- 60CO-irradiation as an alternate method for sterilization of Penicillin G, neomycin, novobiocin, and dihydrostreptomycin
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The effects of the use of 60Co-irradiation to sterilize antibiotics were evaluated. The antibiotic powders were only occasionally contaminated with microorganisms. The D-values of the products and environmental isolates were 0.028, 0.027, 0.015, 0.046, 0.15, 0.018, and 0.19 Mrads for Aspergillus species (UC 7297, 7298), A. fumigatus (UC 7299), Rhodotorula species (UC 7300), Penicillium oxalicum (UC 7269), Pseudomonas maltophilia (UC 6855), and a biological indicator microorganism, Bacillus pumilus spores (ATCC 27142). An irradiation dose of 1.14 Mrads, therefore, was sufficient to achieve a six-log cycle destruction of B. pumilus spores. Based on the bioburden data, a minimum irradiation dose of 1.05 Mrads was calculated to be sufficient to obtain a 10-6 probability of sterilizing the most radioresistant isolate, Pen. oxalicum. To determine the radiolytic degradation scheme and the stability of the antibiotics following irradiation, high-performance liquid chromatographic (HPLC) methods were developed. The resulting rates of degradation for the antibiotics were 0.6, 1.2, 2.3, and 0.95%/Mrad for penicillin G, neomycin, novobiocin, and dihydrostreptomycin, respectively. Furthermore, radiolytic degradation pathways for the antibiotics were identified and found to be similar to those commonly encountered when antibiotics are subjected to acidic, basic, hydrolytic, or oxidative treatments. No radiolytic compounds unique to 60Co-irradiation were found.
- Tsuji,Rahn,Steindler
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Read Online
- New triterpenoid saponin from the stems of Albizia adianthifolia (Schumach.) W.Wight
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As part of our continuing study of apoptosis-inducing saponins from Cameroonian Albizia genus, one new triterpenoid saponin, named adianthifolioside J (1), together with the known gummiferaoside E (2), were isolated from Albizia adianthifolia stems. The s
- Toukea, Daniel Djou,Kamto, Eutrophe Le Doux,Simo, Line Made,Mbing, Joséphine Ngo,Antheaume, Cyril,Haddad, Mohamed,Noté, Olivier Placide,Pegnyemb, Dieudonné Emmanuel
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p. 780 - 788
(2020/08/19)
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- Oleanane-type saponins and prosapogenins from Albizia julibrissin and their cytotoxic activities
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Two undescribed oleanane-type saponins, julibrosides K–L, along with three undescribed oleanane-type prosapogenins, julibrosides M–O, were isolated from the stem bark of Albizia julibrissin Durazz. and the mild alkaline hydrolysate of the total saponin, r
- Han, Qinghua,Qian, Yi,Wang, Xuda,Zhang, Qingying,Cui, Jingrong,Tu, Pengfei,Liang, Hong
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- Synthesis, Radiosynthesis, and in vitro Studies on Novel Hypoxia PET Tracers Incorporating [18F]FDR
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We report the synthesis of five radiotracers incorporating different oxyamine spacers between the hypoxia-reactive 2-nitroimidazole moiety and the 5-[18F]-fluorodeoxyribose ([18F]FDR, 12) prosthetic group: three linear alkyl chains w
- Musolino, Manuele,Fleming, Ian N.,Schweiger, Lutz F.,O'Hagan, David,Dall'Angelo, Sergio,Zanda, Matteo
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p. 1429 - 1439
(2021/02/26)
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- Dihydronicotinamide riboside: synthesis from nicotinamide riboside chloride, purification and stability studies
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In the present work, we describe an efficient method for scalable synthesis and purification of 1,4-dihydronicotinamide riboside (NRH) from commercially available nicotinamide riboside chloride (NRCl) and in the presence of sodium dithionate as a reducing agent. NRH is industrially relevant as the most effective, synthetic NAD+precursor. We demonstrated that solid phase synthesis cannot be used for the reduction of NRCl to NRH in high yield, whereas a reduction reaction in water at room temperature under anaerobic conditions is shown to be very effective, reaching a 55% isolation yield. For the first time, by using common column chromatography, we were able to highly purify this sensitive bio-compound with good yield. A series of identifications and analyses including HPLC, NMR, LC-MS, FTIR, and UV-vis spectroscopy were performed on the purified sample, confirming the structure of NRH as well as its purity to be 96%. Thermal analysis of NRH showed higher thermal stability compared to NRCl, and with two major weight losses, one at 218 °C and another at 805 °C. We also investigated the long term stability effects of temperature, pH, light, and oxygen (as air) on the NRH in aqueous solutions. Our results show that NRH can be oxidized in the presence of oxygen, and it hydrolyzed quickly in acidic conditions. It was also found that the degradation rate is lower under a N2atmosphere, at lower temperatures, and under basic pH conditions.
- Abbaspourrad, Alireza,Enayati, Mojtaba,Khazdooz, Leila,Madarshahian, Sara,Ufheil, Gerhard,Wooster, Timothy J.,Zarei, Amin
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p. 21036 - 21047
(2021/07/01)
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- New dammarane-type triterpenoid saponins from Panax notoginseng leaves and their nitric oxide inhibitory activities
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Inflammation is a very common and important pathological process that can cause many diseases. The discovery of anti-inflammatory drugs and the treatment of inflammation are particularly essential. Dammarane-type triterpenoid saponins (PNS) were demonstrated to show anti-inflammatory effects in the leaves of Panax notoginseng. Chromatographies and spectral analysis methods were combined to isolate and identify PNS. Moreover, the nitric oxide (NO) inhibitory activities of all compounds were examined in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. As a result, eleven new dammarane-type triterpenoid saponins, notoginsenosides NL-A1-NL-A4 (1-4), NL-B1-NL-B3 (5-7), NL-C1-NL-C3 (8-10), and NL-D (11) were isolated, and their structures were identified by using various spectrometric techniques and chemical reactions. Among them, compounds 4 and 11 were characterized by the malonyl substitution at 3-position. The 3-malonyl substituted dammarane-type terpennoids were first obtained from natural products. In addition, compounds 1, 2, 5, 6, and 8-10 were found to play an important role in suppressing NO levels at 50 μM, without cytotoxicity. All inhibitory activities were found to be dose-dependent.
- Hao, Mimi,Ruan, Jingya,Sun, Fan,Wang, Tao,Wu, Lijie,Xiang, Guilin,Yan, Jiejing,Zhang, Yi,Zhang, Ying,Zhao, Wei
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- Lebbeckoside C, a new triterpenoid saponin from the stem barks of Albizia lebbeck inhibits the growth of human glioblastoma cells
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One new acacic acid-type saponin, named lebbeckoside C (1), was isolated from the stem barks of Albizia lebbeck. Its structure was established on the basis of extensive analysis of 1D and 2D NMR (1H, 13C NMR, DEPT, COSY, TOCSY, ROESY, HSQC and HMBC) experiments, HRESIMS studies, and by chemical evidence as 3-O-[β-d-xylopyranosyl-(l→2)-β-d-fucopyranosyl-(1→6)-[β-d-glucopyranosyl(1→2)]-β-d-glucopyranosyl]-21-O-{(2E,6S)-6-O-{4-O-[(2E,6S)-2,6-dimethyl-6-O-(β-d-quinovopyranosyl)octa-2,7-dienoyl]-4-O-[(2E,6S)-2,6-dimethyl-6-O-(β-d-quinovopyranosyl)octa-2,7-dienoyl]-β-d-quinovopyranosyl}-2,6-dimethylocta-2,7-dienoyl}acacic acid 28 O-[β-d-quinovopyranosyl-(l→3)-[α-l-arabinofuranosyl-(l→4)]-α-l-rhamnopyranosyl-(l→2)-β-d-glucopyranosyl] ester. The isolated saponin (1) displayed significant cytotoxic activity against the human glioblastoma cell line U-87 MG and TG1 stem-like glioma cells isolated from a patient tumor with IC50 values of 1.69 and 1.44?μM, respectively.
- Noté, Olivier Placide,Ngo Mbing, Joséphine,Kilhoffer, Marie-Claude,Pegnyemb, Dieudonné Emmanuel,Lobstein, Annelise
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p. 2292 - 2299
(2018/02/26)
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- Isolation, purification, characterization and antioxidant activity of polysaccharides from the stem barks of Acanthopanax leucorrhizus
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A novel water-soluble polysaccharide (named ALP-1) was successfully isolated from the stem barks of Acanthopanax leucorrhizus by hot-water extraction, and further purified by Cellulose DEAE-52 and Sephadex G-100 chromatography. The structure of ALP-1 was characterized by HPLC, HPGPC, partial acid hydrolysis, periodate oxidation, Smith degradation, methylation, together with UV, IR and NMR spectral analysis. The antioxidant activities also were evaluated in vitro. Structural analysis revealed that ALP-1 was a homogeneous galactan with the average molecular weight of 169 kDa, composed of galactose, glucose, mannose and arabinose in a molar ratio of 6.1:2.1:1.1:1.0, owning a backbone structure of 1,6-linked α-D-Galp residues with some branches of α-D-Manp-(1 → 3)-α-L-Araf residues at O-3 and α-D-Galp residues at O-4 of 1,6-linked α-D-Galp. Antioxidant assay showed that ALP-1 exhibited strong DPPH[rad] and HO[rad] scavenging activities, as well as ferric-reducing antioxidant power. These results provide a scientific basis for the further use of polysaccharides from A. leucorrhizus.
- Hu, Hao-Bin,Liang, Hai-Peng,Li, Hai-Ming,Yuan, Run-Nan,Sun, Jiao,Zhang, La-La,Han, Ming-Hu,Wu, Yun
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p. 359 - 367
(2018/05/29)
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- Anti-allergic inflammatory components from Sanguisorba officinalis L.
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Sanguisorba officinalis L. was well known as a traditional herbal medicine to treat inflammation and allergic skin diseases. The aim of this research was to indentify compounds with anti-allergic inflammatory property. Twenty-five compounds (1–25) were isolated from S. officinalis including two new compounds (1 and 8), and their chemical structures were identified by NMR and ESIMS analysis. Consequently, the anti-allergic inflammatory activities of these isolates were investigated by inhibiting β-hexosaminidase and IL-4 production in PMA/A23187-stimulated RBL-2H3 cells. Compounds 6, 8, 13, 17–18 and 25 significantly inhibited β-hexosaminidase release and IL-4 production. Additionally, compounds 8, 17 and 25 effectively suppressed the activation of NF-κB and NF-κB p65 translocation into the nucleus. Anti-inflammatory effects of isolated compounds were evaluated in LPS-stimulated RAW264.7 macrophages, and they showed dramatic inhibition on LPS-induced overproduction of nitric oxide (NO) and TNF-α. Consistently, the protein levels of iNOS and COX-2 were remarkably decreased by the single compounds 8, 13 and 25. These results showed that compounds 8, 13 and 25 from S. officinalis may have a therapeutic potential for allergic inflammatory diseases.
- Su, Xiang Dong,Guo, Rui Hong,Li, Hong Xu,Ma, Jin Yeul,Kim, Young Ran,Kim, Young Ho,Yang, Seo Young
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supporting information
p. 2210 - 2216
(2018/05/23)
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- Melanogenesis-Inhibitory and Cytotoxic Activities of Triterpene Glycoside Constituents from the Bark of Albizia procera
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Five oleanane-type triterpene glycosides including three new ones, proceraosides E-G (1-3), were isolated from a MeOH-soluble extract of Albizia procera bark. The structures of 1-3 were determined by use of NMR spectra, HRESIMS, and chemical methods. Compounds 1-5 exhibited inhibitory activities against the proliferation of the A549, SKBR3, AZ521, and HL60 human cancer cell lines (IC50 0.28-1.8 μM). Additionally, the apoptosis-inducing activity of compound 2 was evaluated by Hoechst 33342 staining and flow cytometry, while the effects of 2 on the activation of caspases-9, -8, and -3 in HL60 cells were revealed by Western blot analysis.
- Zhang, Jie,Akihisa, Toshihiro,Kurita, Masahiro,Kikuchi, Takashi,Zhu, Wan-Fang,Ye, Feng,Dong, Zhen-Huan,Liu, Wen-Yuan,Feng, Feng,Xu, Jian
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supporting information
p. 2612 - 2620
(2019/01/04)
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- Structural and biochemical characterization of the nucleoside hydrolase from C. elegans reveals the role of two active site cysteine residues in catalysis
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Nucleoside hydrolases (NHs) catalyze the hydrolysis of the N-glycoside bond in ribonucleosides and are found in all three domains of life. Although in parasitic protozoa a role in purine salvage has been well established, their precise function in bacteria and higher eukaryotes is still largely unknown. NHs have been classified into three homology groups based on the conservation of active site residues. While many structures are available of representatives of group I and II, structural information for group III NHs is lacking. Here, we report the first crystal structure of a purine-specific nucleoside hydrolase belonging to homology group III from the nematode Caenorhabditis elegans (CeNH) to 1.65? resolution. In contrast to dimeric purine-specific NHs from group II, CeNH is a homotetramer. A cysteine residue that characterizes group III NHs (Cys253) structurally aligns with the catalytic histidine and tryptophan residues of group I and group II enzymes, respectively. Moreover, a second cysteine (Cys42) points into the active site of CeNH. Substrate docking shows that both cysteine residues are appropriately positioned to interact with the purine ring. Site-directed mutagenesis and kinetic analysis proposes a catalytic role for both cysteines residues, with Cys253 playing the most prominent role in leaving group activation.
- Singh, Ranjan Kumar,Steyaert, Jan,Versées, Wim
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p. 985 - 996
(2017/05/01)
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- Bioactive diphenyl ethers and isocoumarin derivatives from a gorgonian-derived fungus Phoma sp. (TA07-1)
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Three new diphenyl ether derivatives-phomaethers A-C (1-3) and five known compounds-including a diphenyl ether analog, 2,30-dihydroxy-4-methoxy-50,6-dimethyl diphenyl ether (4); and four isocoumarin derivatives, diaportinol (5), desmethyldiaportinol (6), citreoisocoumarinol (7), and citreoisocoumarin (8)-were isolated from a gorgonian-derived fungus Phoma sp. (TA07-1). Their structures were elucidated by extensive spectroscopic investigation. The absolute configurations of 1 and 2 were determined by acid hydrolysis reactions. It was the first report to discover the diphenyl glycoside derivatives from coral-derived fungi. Compounds 1, 3, and 4 showed selective strong antibacterial activity against five pathogenic bacteria with the minimum inhibiting concentration (MIC) values and minimum bactericidal concentration (MBC) values between 0.156 and 10.0 μM.
- Shi, Ting,Qi, Jun,Shao, Chang-Lun,Zhao, Dong-Lin,Hou, Xue-Mei,Wang, Chang-Yun
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- New Cytotoxic Triterpenoid Saponins from the Roots of Albizia gummifera (J.F.Gmel.) C.A.Sm.
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As part of our search for new bioactive saponins from Cameroonian medicinal plants, two new oleanane-type saponins, named gummiferaosides D and E (1 and 2), along with one known saponin, julibroside J8 (3), were isolated from the roots of Albizia gummifera. Their structures were established on the basis of extensive 1D- and 2D-NMR (1H- and 13C-NMR, DEPT, COSY, TOCSY, NOESY, HSQC, HSQC-TOCSY, and HMBC) and HR-ESI-MS studies, and by chemical evidence. The apoptotic effect of saponins 1?–?3 was evaluated on the A431 human epidermoid cancer cell. Flow cytometric analyses showed that saponins 1?–?3 induced apoptosis of human epidermoid cancer cell (A431) in a dose-dependent manner.
- Simo, Line Made,Noté, Olivier Placide,Mbing, Joséphine Ngo,Aouazou, Sarah Ali,Guillaume, Dominique,Muller, Christian Dominique,Pegnyemb, Dieudonné Emmanuel,Lobstein, Annelise
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- Acylated oleanane-type triterpene saponins from the flowers of Bellis perennis show anti-proliferative activities against human digestive tract carcinoma cell lines
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Seven oleanane-type triterpene saponin bisdesmosides, perennisaponins N–T (1–7), were newly isolated from a methanol extract of daisy, the flowers of Bellis perennis L. (Asteraceae). The structures were determined based on chemical and physicochemical data and confirmed using previously isolated related compounds as references. The isolates, including 13 previously reported perennisaponins A–M (8–20), exhibited anti-proliferative activities against human digestive tract carcinoma HSC-2, HSC-4, and MKN-45 cells. Among them, perennisaponin O (2, IC50?=?11.2, 14.3, and 6.9?μM, respectively) showed relatively strong activities. The mechanism of action of 2 against HSC-2 was found to involve apoptotic cell death.
- Ninomiya, Kiyofumi,Motai, Chiaki,Nishida, Eriko,Kitagawa, Niichiro,Yoshihara, Kazuya,Hayakawa, Takao,Muraoka, Osamu,Li, Xuezheng,Nakamura, Seikou,Yoshikawa, Masayuki,Matsuda, Hisashi,Morikawa, Toshio
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p. 435 - 451
(2016/07/16)
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- Novel dammarane-type triterpene saponins from Panax ginseng root
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Four phytochemical constituents were isolated from Panax ginseng root by repeated column chromatography (CC), medium pressure liquid chromatography (MPLC), high-speed counter current chromatography (HSCCC), and semi-preparative HPLC. Their structures were elucidated as the dammarane-type triterpene saponins ginsenoside-Rg18 (1), 6-acetyl ginsenoside-Rg3 (2), ginsenoside-Rs11 (3), and ginsenoside-Re7 (4) based on spectral data. Compounds 1-4 from P. ginseng root were new compounds from nature. They showed good hydroxyl radical scavenging activity and anti-bacterial activity against Escherichia coli and Staphylococcus aureus. However, they did not show any anti-inflammatory activity. In addition, they inhibited the growth of adenocarcinoma gastric stomach cells. Among them, ginsenoside-Rs11 (3) showed the best anti-oxidative, anti-bacterial, and anti-cancer activities.
- Lee, Dong Gu,Lee, Ah Young,Kim, Kyung-Tack,Cho, Eun Ju,Lee, Sanghyun
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p. 927 - 934
(2016/02/03)
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- A general and enantioselective approach to pentoses: A rapid synthesis of PSI-6130, the nucleoside core of sofosbuvir
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An efficient route towards biologically relevant pentose derivatives is described. The de novo synthetic strategy features an enantioselective α-oxidation reaction enabled by a chiral amine in conjunction with copper(II) catalysis. A subsequent Mukaiyama aldol coupling allows for the incorporation of a wide array of modular two-carbon fragments. Lactone intermediates accessed via this route provide a useful platform for elaboration, as demonstrated by the preparation of a variety of C-nucleosides and fluorinated pentoses. Finally, this work has facilitated expedient syntheses of pharmaceutically active compounds currently in clinical use.
- Peifer, Manuel,Berger, Rapha?lle,Shurtleff, Valerie W.,Conrad, Jay C.,Macmillan, David W. C.
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supporting information
p. 5900 - 5903
(2014/05/20)
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- A new flavonol glycoside from the aerial part of Rudbeckia laciniata
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The phytochemical investigation of Rudbeckia laciniata L. obtained a new flavonol glycoside (1), together with four flavonol glycosides (2-5) and eight quinic acid derivatives (6-13). The structure was elucidation by means of spectroscopic methods and chemical evidence. The isolated compounds were tested for cytotoxicity against four human tumor cell lines in vitro using the sulforhodamine B bioassay.
- Lee, Seung Young,Shin, Young June,Choi, Sang Un,Lee, Kang Ro
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p. 834 - 838
(2014/08/05)
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- Mandshunosides C-E from the roots and rhizomes of Clematis mandshurica
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Abstract Three new triterpene saponins, mandshunosides C-E (1-3) together with four known triterpene saponins (4-7) were isolated from the roots and rhizomes of Clematis mandshurica. Their structures were elucidated on the basis of spectroscopic evidence
- Li, Ling,Gou, Mei-Ling,He, Yu-Xin
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p. 570 - 574
(2013/10/08)
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- Cytotoxic triterpenoid saponins from Aesculus glabra Willd.
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Twenty-four acylated polyhydroxyoleanene saponins were isolated from the seeds of Aesculus glabra. Sixteen of them, namely aesculiosides G1-G16 (1-16), were determined as compounds by spectroscopic and chemical analysis. The structural features of all 24 saponins are: (1) arabinofuranosyl units affixed to C-3 of the glucuronopyranosyl unit in the trisaccharide chain; (2) no 24-OH substitution; (3) C-2 sugar moiety substitution of the 3-O-glucuronopyranosyl unit is either glucopyranosyl or galactopyranosyl. The features of these isolated saponin structures provide more evidence for chemical taxonomy within the genus Aesculus. The cytotoxicity of the aesculiosides (1-16) were tested against A549 and PC-3 cancer cell lines with GI50 from 5.4 to >25 μM.
- Yuan, Wei,Wang, Ping,Deng, Guangrui,Li, Shiyou
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experimental part
p. 67 - 77
(2012/04/04)
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- Hydrolytic hydrogenation of hemicellulose over metal modified mesoporous catalyst
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The hydrolytic hydrogenation of hemicellulose arabinogalactan, into sugars, sugar alcohols and furfurals was carried out in a batch reactor using modified mesoporous MCM-48 material incorporated with ruthenium metal into the framework. The bi-functional catalytic materials, MCM-48 and Ru-MCM-48 were synthesized, characterized and investigated in the title reaction at total pressure of 20 bar hydrogen, using an initial arabinogalactan concentration of 0.4 wt%, at 458 K. The transformation of the hemicellulose consists of arabinogalactan hydrolysis to the monosaccharides, l-arabinose and d-galactose followed by the subsequent hydrogenation to sugar alcohols, arabitol and galactitol or dehydration of the monomers to furfural and 5-hydroxymethylfurfural. The yields of the main products, i.e. sugars, sugar alcohols and furfurals were varied depending on the strength of the acid sites and the presence of metal in the structure of the ruthenium modified catalyst. Ru-MCM-48 displayed high catalytic activity and the sugar alcohols were obtained selectively from the hemicellulose. The catalytic performance of the mesoporous MCM-48 catalysts with respect to the catalyst structure, acidity and presence of the metal was evaluated.
- Kusema, Bright T.,Faba, Laura,Kumar, Narendra,M?ki-Arvela, P?ivi,Díaz, Eva,Ordó?ez, Salvador,Salmi, Tapio,Murzin, Dmitry Yu.
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- Steroidal saponins from Paris polyphylla var. yunnanensis
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Eleven steroidal saponins, along with seven known steroidal saponins, were isolated from rhizomes of Paris polyphylla var. yunnanensis. Their chemical structures were elucidated on the basis of spectroscopic analyses and acid hydrolysis. Two of these compounds contained a spirostanol saponin aglycone, hitherto unknown in Nature. The isolated compounds were tested for their cytotoxic effects on human nasopharyngeal carcinoma epithelial (CNE) cells, and seven compounds displayed more potent inhibitory effects than cisplatin (the positive control). One compound with diosgenin and tetrasaccharide moieties possessed the strongest inhibitory effect on CNE cells through the induction of apoptosis and cell cycle arrest.
- Wu, Xia,Wang, Lei,Wang, Hui,Dai, Yi,Ye, Wen-Cai,Li, Yao-Lan
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experimental part
p. 133 - 143
(2012/10/08)
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- Antioxidant activity of a new C-glycosylflavone from the leaves of Ficus microcarpa
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By bioactive-guided fractionation of methanol extract of the Ficus microcarpa leaves, one new C-glucosylflavone, ficuflavoside (1), one new megastigmane glycoside, ficumegasoside (8), and twelve known compounds including flavonoids (2-6), phenylpropanoids (7), megastigmanes (9-11) and sterol derivatives (12-14) were isolated. Their chemical structures were elucidated by mass, 1D, and 2D NMR spectroscopies. The antioxidant activities of these compounds were measured using the oxygen radical absorbance capacity methods. Compounds 1-6 exhibited potent antioxidant activities of 6.6-9.5 μM Trolox equivalents at the concentration of 2.0 μM. The results indicated 2, 3, and 5 having meaningful reducing capacity of copper (I) ions concentration of 6.1-8.4 μM.
- Kiem, Phan Van,Cuong, Nguyen Xuan,Nhiem, Nguyen Xuan,Thu, Vu Kim,Ban, Ninh Khac,Minh, Chau Van,Tai, Bui Huu,Hai, Truong Nam,Lee, Sang Hyun,Jang, Hae Dong,Kim, Young Ho
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experimental part
p. 633 - 637
(2011/02/27)
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- Purification, characterization and mass spectrometric identification of two thermophilic xylanases from Sporotrichum thermophile
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Two xylanases were purified to electrophoretic homogeneity from the thermophilic fungus Sporotrichum thermophile grown in a submerged liquid culture using wheat straw as carbon source. The enzymes, StXyn1 and StXyn2, have molecular masses of 24 kDa and 48 kDa, respectively, and are optimally active at pH 5 and at 60 °C. Both enzymes displayed remarkable stability up to 50 °C for 1 h, exhibiting a half-life of 60 min (StXyn1) and 115 min (StXyn2) at 60 °C. Biochemical characterization of the two xylanases against poly- and oligosaccharides indicated that StXyn1 and StXyn2 hydrolytic profiles match those of xylanase family 11 and family 10, respectively. LC-MS/MS analysis provided peptide mass and sequence information that assisted the identification of the corresponding xylanase genes from the S. thermophile genome and the classification of the two purified StXyn1 and StXyn2 as a family GH11 and GH10 endo-1,4-β-xylanases, respectively.
- Vafiadi, Christina,Christakopoulos, Paul,Topakas, Evangelos
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experimental part
p. 419 - 424
(2011/10/31)
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- Synthesis of 5′-seleno-xylofuranosides
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The synthesis of selenium derivatives of naturally occurring chiral molecules is becoming increasingly important in recent years. In this context, we describe herein an easy, straightforward synthetic route for the preparation of a series of chiral seleno-furanosides, starting from the readily available carbohydrate d-xylose. In addition, selected compounds were screened as inhibitors of the δ-aminolevulinate dehydratase (δ-ALA-D) enzyme. Diselenide 4 was found to reduce significantly the enzymatic activity, while seleno-furanoside 1a increased δ-ALA-D activity.
- Braga, Hugo C.,Stefani, Hélio A.,Paix?o, Márcio W.,Santos, Francielli W.,Lüdtke, Diogo S.
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body text
p. 3441 - 3446
(2010/06/19)
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- A novel pentose synthesis via palladium(II)-catalyzed cyclization of an unstable hemiacetal
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PdCl2(PhCN)2 (5 mol%)-catalyzed cyclization of a hemiacetal derived from (E,2S,3R)-2,3-isopropylidenedioxy-6-(tetrahydro-2H- pyran-2-yl)-4-hexenal and methanol gave substituted furanoside in moderate yield, exclusively via 5-exo-mode cyclization, without the need for a reoxidant. New stereogenic centers at C1 and C4 on the tetrahydrofuran ring showed preferential 1R and 4R stereochemistry due to anomeric effect (n oσ*c-o) and A1,2 strain, respectively. This methodology was applied to stereocontrolled synthesis of pentoses: D-ribose and L-lyxose. The Japan Institute of Heterocyclic Chemistry.
- Awasaguchi, Ken-Ichiro,Miyazawa, Masahiro,Uoya, Ikuyo,Inoue, Koichi,Nakamura, Koji,Yokoyama, Hajime,Hirai, Yoshiro
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p. 2105 - 2121
(2011/04/24)
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- New benzophenone and quercetin galloyl glycosides from Psidium guajava L.
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New benzophenone and flavonol galloyl glycosides were isolated from an 80% MeOH extract of Psidium guajava L. (Myrtaceae) together with five known quercetin glycosides. The structures of the novel glycosides were elucidated to be 2,4,6-trihydroxybenzophenone 4-O-(6′-O-galloyl)-β-D- glucopyranoside (1, guavinoside A), 2,4,6-trihydroxy-3,5-dimethylbenzophenone 4-O-(6′-Ogalloyl)-β-D-glucopyranoside (2, guavinoside B), and quercetin 3-O-(5′-O-galloyl)-a-L-arabinofuranoside (3, guavinoside C) by NMR, MS, UV, and IR spectroscopies. Isolated phenolic glycosides showed significant inhibitory activities against histamine release from rat peritoneal mast cells, and nitric oxide production from a murine macrophage- like cell line, RAW 264.7. The Author(s) 2010.
- Matsuzaki, Keiichi,Ishii, Rie,Kobiyama, Kaori,Kitanaka, Susumu
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experimental part
p. 252 - 256
(2011/02/28)
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- New glycosidic constituents of abutilon Pakistanicum
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Pakisides A and B (1 and 2, resp.), new catalpol-type iridoid glycosides, and a new glycoside, 3, of scutellarein have been isolated from the AcOEt-soluble fraction of the whole plant of Abutilon pakistanicum, along with buddlejoside and lapachol. The structures of new compounds were elucidated by spectroscopic techniques including 1H-and 13C-NMR (DEPT), and 2D-NMR experiments. Copyright 2010 Verlag Helvetica Chimica Acta AG, Zuerich, Switzerland.
- Ali, Bakhat,Fatima, Itrat,Malik, Abdul,Ahmed, Zaheer
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experimental part
p. 2245 - 2250
(2011/01/12)
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- A method for the rapid discovery of naturally occurring products by proteins immobilized on magnetic beads and reverse affinity chromatography
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A highly efficient screening method for naturally occurring products that bind to a specific target protein was demonstrated by using hVDR magnetic beads. The native ligand 1α, 25(OH)2 VD3 (1) was selectively bound by hVDR magnetic b
- Arai, Midori A.,Kobatake, Eiji,Koyano, Takashi,Kowithayakorn, Thaworn,Kato, Shigeaki,Ishibashi, Masami
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experimental part
p. 1802 - 1808
(2010/04/30)
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- β-D-ribosidase activity indicators with a chromogenic substrate
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This invention provides a method of detecting enzyme activity on a solid medium. The enzyme substrate has a chromogenic portion comprising a catechol residue, in which a derivitising moiety is linked to the aromatic ring of the catechol via a bond, and an enzyme cleavable group which is attached via an ester or ether linkage to the oxygen atom derived from a hydroxyl group of the catechol residue. If the enzyme substrate contacts an enzyme capable of cleaving the enzyme cleavable groups and the cleaved compound contacts a chelatable metal ion, a substantially non-diffusable coloured precipitate is formed.
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Page/Page column 18-19
(2009/05/29)
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- New terpenoids from Stachys parviflora Benth
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Two new triterpenoidal saponins were isolated from the n-butanolic extract of Stachys parviflora (Lamiaceae). Their structures were elucidated on the basis of spectral data as stachyssaponin A; 3β, 15α, 19α, 21β, 22α-pentahydroxyolean-12-ene-28-oic acid 3-O-{α-L-rhamnopyranosyl-(1 → 3)-β-D-glucopyranoside)-22-O-{α-L-arabinofuranosyl-(1 → 3)-β-D-glucopyranoside) (1) and stachyssaponin B; 2β, 3β, 15α, 21β-tetrahydroxyolean-12-ene-28-oic acid 2-O-[a-L- arabinofuranoside]-3, 21-bis-O-[β-D-glucopyranoside] (2). Copyright
- Ahmad, Viqar Uddin,Arshad, Saima,Bader, Sadia,Iqbal, Shazia,Khan, Afsar,Khan, Saleha Suleman,Hussain, Javid,Tareen, Rasool Bakhsh,Ahmed, Amir
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experimental part
p. 986 - 989
(2009/05/30)
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- Nucleoside synthesis from 3-alkylated sugars: Role of 3β-oxy substituents in directing nucleoside formation
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Using Vorbrueggen's protocol, reaction of persilylated uracil with xylofuranose derivatives having 3β-oxy-3α-alkyl substitution produced both α- and β-nucleosides. Only the β-nucleosides were formed from substrates having the reverse stereochemistry at C-3 or lacking the 3-alkyl substituent. Participation of the 3β-oxy substituent in stabilizing the incipient C-1 carbonium ion (or oxonium ion) intermediate has been suggested from analysis of energy-minimized conformations. The Royal Society of Chemistry 2006.
- Sahabuddin, Sk.,Ghosh, Ramprasad,Achari, Basudeb,Mandal, Sukhendu B.
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p. 551 - 557
(2008/02/02)
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- Phosphate activation in the ground state of purine nucleoside phosphorylase
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Phosphate and ribose 1-phosphate (R1P) bound to human purine nucleoside phosphorylase (PNP) have been studied by FTIR spectroscopy for comparison with phosphate bound with a transition state analogue. Bound phosphate is dianionic but exists in two distinct binding modes with similar binding affinities. The phosphate of bound R1P is also dianionic. Bound R1P slowly hydrolyzes to ribose and phosphate even in the absence of nucleobase. The C-OP bond is cleaved in bound R1P, the same as in the PNP-catalyzed reaction. Free R1P undergoes both C-OP and CO-P solvolysis. A hydrogen bond to one P-..O group is stronger than those to the other two P-..O groups in both the PNP·R1P complex and in one form of the PNP·PO4 complex. The average hydrogen bond strength to the P-..O bonds in the PNP·R1P complex is less than that in water but stronger than that in the PNP·PO4 complex. Hydrolysis of bound R1P may be initiated by distortion of the phosphate moiety in bound R1P. The unfavorable interactions on the phosphate moiety of bound R1P are relieved by dissociation of R1P from PNP or by hydrolysis to ribose and phosphate. The two forms of bound phosphate in the PNP·PO4 complex are interpreted to be phosphate positioned as the product in the nucleoside synthesis direction and as the reactant in the phosphorolysis reaction; their interconversion can occur by the transfer of a proton from one PO bond to another. The electronic structure of phosphate bound with a transition state analogue differs substantially from that in the Michaelis complexes.
- Deng, Hua,Murkin, Andrew S.,Schramm, Vern L.
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p. 7765 - 7771
(2007/10/03)
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- Mitochondrially targeted antioxidants
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The invention provides mitochondrially targeted antioxidant compounds comprising a lipophilic cation moiety covalently coupled to a glutathione peroxidase mimetic. These compounds can be used to treat patients who would benefit from the reduction of oxidative stress.
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- Biosynthesis of the thiamin pyrimidine: The reconstitution of a remarkable rearrangement reaction
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The conversion of 5-aminoimidazole ribonucleotide (AIR) into 4-amino-2-methyl-5-hydroxymethylpyrimidine (HMP) is a fascinating reaction on the thiamin biosynthetic pathway in bacteria and is probably the most complex unresolved rearrangement in primary metabolism. We have successfully reconstituted this reaction in a cell-free system. The E. coli thiC gene product and an additional unidentified E. coli protein are required for the reaction. In addition, SAM and nicotinamide cofactors are required for full activity. Labeling studies to determine the origin of most of the atoms in the pyrimidine are described. Based on these studies, a new mechanism for HMP formation is proposed.
- Lawhorn, Brian G.,Mehl, Ryan A.,Begley, Tadhg P.
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p. 2538 - 2546
(2007/10/03)
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- Adenosine Kinase Inhibitors. 3. Synthesis, SAR, and Antiinflammatory Activity of a Series of L-Lyxofuranosyl Nucleosides
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Chronic inflammatory diseases, such as arthritis and rheumatoid arthritis, remain major health problems worldwide. We previously demonstrated that adenosine kinase inhibitors (AKIs) exhibit antiinflammatory effects by inhibiting TNF-α production, neutroph
- Ugarkar, Bheemarao G.,Castellino, Angelo J.,DaRe, Jay S.,Ramirez-Weinhouse, Michele,Kopcho, Joseph J.,Rosengren, Sanna,Erion, Mark D.
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p. 4750 - 4760
(2007/10/03)
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- Substrate specificity of the α-L-arabinofuranosidase from Rhizomucor pusillus HHT-1
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The α-L-arabinofuranosidase (AF) from the fungus Rhizomucor pusillus HHT-1 released arabinose at appreciable rates from (1→5)-α-L-arabinofuranooligosaccharides, sugar beet arabinan and debranched arabinan. This enzyme preferentially hydrolyzed the terminal arabinofuranosyl residue [α-(1→5)-linked] of the arabinan backbone rather than the arabinosyl side chain [α-(1→3)-linked residues]. The enzyme-hydrolyzed arabinan reacted at and debranched the arabinan almost at the same rate, and the degree of conversion for both cases was 65%. Methylation analysis of arabinan showed that the arabinosyl-linkage proportions were 2:2:2:1, respectively, for (1→5)-Araf, T-Araf, (1→3, 5)-Araf and (1→3)-Araf, while the ratios for the AF-digested arabinan shifted to 3:1:2:1. Enzyme digestion resulted in an increase in the proportion of (1→5)-linked arabinose and a decrease in the proportion of terminal arabinose indicated this AF cleaved the terminal arabinosyl residue of the arabinan back bone [α-(1→5)-linked residues]. Peak assignments in the 13C NMR spectra also confirmed this linkage composition of four kinds of arabinose residues. Both 1H and 13C NMR spectra are dominated by signals of the α-anomeric configuration of the arabinofuranosyl moieties. No signals were recorded for arabinopyranosyl moieties in the NMR spectra. Methylation and NMR analysis of native and AF-digested arabinan revealed that this α-L-arabinofuranosidase can only hydrolyse α-L-arabinofuranosyl residues of arabinan.
- Rahman, A.K.M. Shofiqur,Kato, Koji,Kawai, Shingo,Takamizawa, Kazuhiro
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p. 1469 - 1476
(2007/10/03)
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- Studies on kinetics and mechanism of iridium(III) catalysed cerium(IV) oxidation of D-mannitol and D-glucose in aqueous acid media
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The kinetics and mechanism of Ce(IV) oxidation of D-mannitol and D-glucose in aqueous H2SO4 media in the presence and absence of Ir(III) have been studied and compared under the conditions. [S]T?[Ce(IV)]T?[Ir]T, where [S]T gives the total substrate (D-mannitol or D-glucose) concentration and [Ir]T denotes the total concentration of Ir(III) catalyst added. Ir(III) has been found to catalyse the title reactions very efficiently even at trace concentration (ca. 10-6 to 10-7 mol dm-3). Under the kinetic conditions, both the uncatalysed and catalysed reactions take place simultaneously. The overall process shows a first order dependence on [Ce(IV)] and [S]T. The catalytic path is first order in [Ir]T suggested to involve the Ir(III)/Ir(IV) catalytic cycle. The process is acid catalysed and inhibited by [HSO4]. From the HSO4 dependence, both Ce(SO4)2+ and Ce(SO4)2 have been found kinetically active in D-mannitol oxidation while in D-glucose oxidation Ce(SO4)2 is the main kinetically active species under comparable conditions. The different kinetic parameters for both the Ir(III) catalysed and uncatalysed paths have been estimated.
- Roy, Aparna,Das, Asim K.
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p. 2468 - 2474
(2007/10/03)
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- New cycloartane and flavonol glycosides from Corchorus depressus
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Two new monodesmosidic cycloartane triterpene glycosides, depressosides E and F, and two new flavonol glycosides, depressonol A and B, were isolated from the butanol-soluble part of the EtOH extract of Corchorus depressus L. The structures of the new comp
- Zahid, Muhammad,Ali, Akbar,Ishurd, Omar,Ahmed, Amir,Ali, Zulfiqar,Ahmad, Viqar Uddin,Pan, Yuanjiang
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p. 689 - 697
(2007/10/03)
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- Metal ion-promoted cleavage of mRNA 5′-cap models: Hydrolysis of the triphosphate bridge and reactions of the N7-methylguanine base
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Reactions of mRNA 5′-cap model compounds were studied to evaluate the potential of these reactions in the development of artificial RNases. Diadenosine triphosphate was used as a model for the triphosphate bridge, and its hydrolysis was studied in the pre
- Valakoski, Satu,Heiskanen, Suvi,Andersson, Sanna,L?hde, Mari,Mikkola, Satu
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p. 604 - 610
(2007/10/03)
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- The stability of 6-mercaptopurine riboside in neutral and basic medium
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The kinetics of hydrolysis of 6-mercaptopurine riboside (R-6-MP) was studied in aqueous solutions over the pH range of 6.11 - 12.13 at 353 K. The decomposition was investigated by HPLC method. At the pH range from 6.11 to 12.13 hydrolysis of 6-mercaptopurine riboside includes: spontaneous hydrolysis of non-protonated R-6-MP molecules mono- and di-anions R-6-MP molecules under the effect of water.
- Jelinska,Magdziarz
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p. 407 - 409
(2007/10/03)
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- Stability of disodium salt of inosine phosphate in aqueous solutions
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The HPLC method for the separation of the disodium salt of inosine phosphate (PIN) and the product of its transformation, inosine (IN) and hypoxanthine (HP) were developed and validated. The hydrolysis kinetics of disodium salt of inosine phosphate was studied in aqueous solution at 353 K over a pH range of 0,45-12,13.
- Jelinska,Lewandowski
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p. 331 - 335
(2007/10/03)
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- Isolation and properties of glucose-1-phosphatase from mycelia of Pholiota nameko.
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An acid phosphatase with a very high substrate specificity for glucose-1-phosphate was isolated for the first time from mycelia of Pholiota nameko. The molecular weight of the enzyme was estimated to be 31,000 on gel filtration and 35,000 on SDS-PAGE. The activity was inhibited by Cu2+, Hg2+, molybdate, and tartaric acid. The sequence of N-terminal 20 amino acid residues was analyzed.
- Joh,Yazaki,Suzuki,Hayakawa
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p. 2251 - 2253
(2007/10/03)
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- Electrochemical and peroxidase catalysed oxidation of 9-β-D-ribofuranosyluric acid 5′-monophosphate
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The electrochemical oxidation of 9-β-D-ribofuranosyluric acid 5′-monophosphate (UA-9R-5′-P) in aqueous solution has been studied in the pH range 2.10-10.0. The evidence strongly indicates that UA-9R-5′-P is oxidized in a 2e-, 2H+ reaction to give an unstable diimine which subsequently decomposes. A UV absorbing intermediate is observed during electrooxidation which decays in a pseudo first-order reaction to give alloxan, urea and ribosyl phosphate at pH 3.0. Controlled potential electrolysis results in the transfer of 2.0 ± 0.2 electrons per molecule and three major products are obtained at pH 7.0; allantoin, 5-hydroxyhydantoin-5-carboxamide and D-ribose. Tentative reaction schemes are proposed to explain the formation of these products. Oxidation of UA-9R-5′-P in the presence of peroxidase and H2O2 also generates an intermediate which has spectral and kinetic properties identical to those of the intermediate generated electrochemically. Thus, it is believed that electrochemical and enzymic oxidation of UA-9R-5′-P proceed by identical reaction mechanisms.
- Goyal, Rajendra N.,Rastogi, Arshi
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p. 2423 - 2429
(2007/10/03)
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- Chemical evaluation of Betula species in Japan. I. Constituents of Betula ermanii
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The constituents of Betula ermanii CHAM. in Japan were identified as follows. Fresh leaves: 20(S),24(R)-epoxydammmaran-3β,11α,25-triol (1), 3- O-β-D-glucopyranoside of 1 (2), 2'-acetate of 2 (3), 11,2'-diacetate of 2 (4), dammar-24-en-3β,11α,20(S)-triol (5), 3-O-β-D-2-O- acetylglucopyranoside of 5 (6). Outer bark: betulin (7), betulin 3-caffeate (8), oleanolic acid (9). Inner bark: (+)-lyoniresinol 3α-O-α-L- rhamnopyranoside (10), (-)-lyoniresinol 3α-O-β-D-xylopyranoside (11), 9,9'- di-O-feruloyl-(-)-secoisolariciresinol (12), acerogenin E (13), 3,4,5- trimethoxyphenol β-D-apiofuranosyl-(1→6)-β-D-glucopyranoside (14), 4-(4- hydroxyphenyl)-2-butanol 2-O-β-D-apiofuranosyl-(1→6)-β-D-glucopyranoside (15), (+)-catechine 7-O-β-D-xylopyranoside (16), lupeol (17), monogynol A (18). Root outer bark: lupeol caffeate (19), betulin 3-caffeate (8), oleanolic acid caffeate (20), dammarendiol II 3-caffeate (21). Compounds 2, 3, 4, 6, 19 and 21 are new.
- Fuchino,Satoh,Tanaka
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p. 1937 - 1942
(2007/10/03)
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- Mode of action of (1→4)-β-D-arabinoxylan arabinofuranohydrolase (AXH) and α-L-arabinofuranosidases on alkali-extractable wheat-flour arabinoxylan
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Arabinoxylan-derived oligosaccharides were treated with (1→4)-β-D-arabinoxylan arabinofuranohydrolase (AXH) and two types of α-L-arabinofuranosidase, A and B. Analysis of reaction products by high performance anion-exchange chromatography indicated the removal of arabinofuranosyl groups from singly substituted xylopyranosyl residues. In addition, differences in the specificity of these enzymes towards the various differently substituted oligosaccharides were observed. 1H NMR spectroscopy and methylation analysis of alkali-extractable wheat-flour arabinoxylan treated with AXH confirmed the specificity of AXH towards (1→3)-linked arabinofuranosyl groups on singly substituted xylopyranosyl residues. With these techniques, α-L-arabinofuranosidase B was found to cause minor changes in (1→2)- and (1→3)-linked arabinofuranosyl groups on doubly substituted xylopyranosyl residues. Arabinoxylan-derived oligosaccharides were treated with (1 → 4)-B-D-arabinoxylan arabinofuranohydrolase (AXH) and two types of A-L-arabinofuranosidase, A and B. Analysis of reaction products by high performance anion-exchange chromatography indicated the removal of arabinofuranosyl groups from singly substituted xylopyranosyl residues. In addition, differences in the specificity of these enzymes towards the various differently substituted oligosaccharides were observed. 1H NMR spectroscopy and methylation analysis of alkali-extractable wheat-flour arabinoxylan treated with AXH confirmed the specificity of AXH towards (1 → 3)-linked arabinofuranosyl groups on singly substituted xylopyranosyl residues. With these techniques, A-L-arabinofuranosidase B was found to cause minor changes in (1 → 2) and (1 → 3) linked arabinofuranosyl groups on doubly substituted xylopyranosyl residues.
- Kormelink,Gruppen,Voragen
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p. 345 - 353
(2007/10/02)
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- New method of synthesis of D-ribose and D-lyxose
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An attempt has been made to synthesize D-ribose from D-xylose using only commercial products and a minimum number of steps. D-xylose was transformed into pentenofuranoside which then was hydrolyzed. In the pyranose series, the unsaturated derivative could
- Lacourt-Gadras,Grignon-Dubois,Rezzonico
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p. 281 - 288
(2007/10/02)
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- Kinetics of oxidation of some monosaccharides by pyridinium chlorochromate (PCC)
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The oxidation kinetics of glucose, considered as a model compound for reducing sugars, with pyridinium chlorochromate in perchloric acid medium has revealed a linear correlation between the observed rate constant kobs and , +>.A comparison of D-glucose oxidation with its various C-1 and C-2 substituted derivatives shows that inductive, steric and shielding effects may all be important which explains the reactivity as 2-deoxy-D-glucose above D-glucose above 1-o-methyl-α-D-glucopyranoside above 2-amino-2-deoxy-D-glucose hydrochloride.A comparison between α and β-anomers of some monosaccharides reveals that β-anomer is oxidised faster than α-anomers.Further, activation energy and thermodynamic parameters have been evaluated for D-glucose oxidation and mechanism consistent with experimental observation is attempted.
- Dhar, Raj K
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- Ionization of purine nucleosides and nucleotides and their components by 193-nm laser photolysis in aqueous solution: Model studies for oxidative damage of DNA 1
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The effect of 20-ns pulses of 193-nm laser light on aqueous solutions of purine bases, (2′-deoxy)nucleosides, and (2′-deoxy)nucleotides was investigated, and monophotonic ionization was observed. Although (deoxy)ribose and (deoxy)ribose phosphates are also ionized by 193-nm light, the photoionization of the (deoxy)nucleosides and -tides takes place predominantly (90%) at the purine moiety, due to the much higher extinction coefficients at 193 nm of the bases as compared to the (deoxy)ribose phosphates. The quantum yields of photoionization (φPl) of the purines are in the range 0.01 to 0.08, based on φ(Cl-) at 193 nm of 0.46. As shown by comparison with data obtained from pulse radiolysis, the ionized purines, i.e., the radical cations, deprotonate in neutral solution, yielding neutral radicals. The radical cation of 1-methylguanosine, produced by photoionization in oxygen-saturated aqueous solution, deprotonates with the rate constant 3.5 × 105 s-1. In the absence of oxygen, the hydrated electrons resulting from the photoionization react with the untransformed purine derivatives to yield the corresponding radical anions. As these are rapidly protonated by water (as concluded from pulse radiolysis), the photoionization in deaerated neutral solution results in two different neutral radicals: a deprotonated radical cation and a protonated radical anion.
- Candeias,Steenken
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p. 699 - 704
(2007/10/02)
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- The 18O Isotope Shift in 13C Nuclear Magnetic Resonance Spectroscopy. 14. Kinetics of Oxygen Exchange at the Anomeric Carbon of D-Ribose and D-2-Deoxyribose
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The kinetics of the oxygen-exchange reaction at the anomeric carbon atoms of D-ribose and D-2-deoxyribose (2-deoxy-D-erythro-pentose) were compared using the 18O isotope induced shift in 13C NMR spectroscopy.Measurements were made at a number of temperature and pH values.The oxygen-exchange reaction for these sugars is strongly pH-dependent, displaying regions of acid, water, and base catalysis.At 25 deg C the oxygen-exchange rate of D-ribose was found to be approximately 20-fold greater than the rate for D-glucose between pH 2 and 9.In turn, the oxygen-exchange rate for D-2-deoxyribose was greater than the rate for D-ribose by approximately 5-fold above pH 4 and by greater than 10-fold below pH 4.The results are analyzed in terms of steric and inductive effects on the hydration kinetics of the open-chain forms and by comparison with the hydration reaction of simple aldehydes.The study also includes quantitative data, based upon 13C NMR line intensities, for the various anomeric forms that exist in solutions of these sugars at the different temperature and pH values used in the kinetic measurements reported here.In each case, the oxygen-exchange reactions of the anomers are slow relative to the rate of anomerization, so that the anomers appear to exchange oxygen at the same rate.
- Cortes, Sergio J.,Mega, Tony L.,Etten, Robert L. van
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p. 943 - 947
(2007/10/02)
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