- 5,6,7-TRISUBSTITUTED FLAVONES FROM GOMPHRENA MARTIANA
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Two 5,6,7-trisubstituted flavones have been isolated from Gomphrena martiana and indentified as 5,6-dimethoxy-7-hydroxyflavone and 5,6-dihydroxy-6-methoxyflavone.Key Word Index -Gomphrena martiana; Amaranthaceae; flavonoids; 5,6-dimethoxy-7-hydroxyflavone; 5,7-dihydroxy-6-methoxyflavone.
- Buschi, C. A.,Pomilio, A. B.,Gros, E. G.
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- An unambiguous and practical synthesis of Oroxylin A: a commonly misidentified flavone
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Oroxylin A, a major flavonoid in the extracts of Oroxylum indicum as well as Scutellaria baicalensis possesses useful medicinal properties. Many of the published routes claiming the synthesis of Oroxylin A (1) have in fact led to a regioisomer Negletein that was misinterpreted as Oroxylin A. In the present work, we describe a novel, straight-forward and scalable semi-synthetic approach for rapid access to the title compound, the structure of which is unambiguously secured by NMR and X-ray crystallographic analysis of a derivative. This work also encompasses the synthesis of a glycosylated derivative of Oroxylin A viz OAGME (2), which has marked pharmacological importance.
- Hemantha, Hosahalli P.,Ramanujam, Rajendran,Majeed, Muhammed,Nagabhushanam, Kalyanam
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p. 1413 - 1420
(2019/08/22)
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- Synthetic method of oroxylin
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The invention relates to a synthetic method of oroxylin. The method disclosed by the invention comprises the following steps: carrying out acetylation reaction on 5, 6, 7-trihydroxy flavone and aceticanhydride in pyridine at room temperature; reacting an obtained acetylate with benzyl bromide or benzyl chloride in the presence of an inorganic base, and carrying out hydrolysis reaction on a product in alkaline water; and reacting with methyl iodide in the presence of an inorganic base, and finally debenzylating in the presence of concentrated sulfuric acid to obtain the target product oroxylin. The method for synthesizing oroxylin provided by the invention has the advantages of simple and feasible operation, high product purity, high reaction yield and the like, and is easier for industrial production compared with the existing method.
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- Crystal structures of the flavonoid Oroxylin A and the regioisomers Negletein and Wogonin
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The flavonoid Oroxylin A (6-methoxychrysin or 5,7-dihydroxy-6-methoxy-2- phenyl-4H-chromen-4-one, C16H12O5) and its regioisomers are of increasing interest for a variety of bioactive functions and their pharmaceutical formulation is of importance. Previous difficulties in the separation and misidentification of Oroxylin A from its regioisomers Wogonin (8-methoxychrysin or 5,7-dihydroxy-8-methoxy-2-phenyl-4H-chromen-4-one) and Negletein (5,6- dihydroxy-7-methoxyflavone or 5,6-dihydroxy-7-methoxy-2-phenyl-4H-chromen- 4-one) render its full structural and powder X-ray characterization highly desirable. The low-temperature (100 K) crystal structures of Oroxylin A, Negletein and Wogonin sesquihydrate are reported for the first time. Wogonin crystallizes in two related but distinct hydrated forms. These have very similar powder diffractograms, indicating that such issues need to be addressed for its pharmaceutical formulation.
- Grano, Ruel Valerio Robles De,Nisar, Madiha,Sung, Herman H.-Y.,Vashchenko, Elena V.,Vashchenko, Valerii V.,Williams, Ian D.
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p. 490 - 499
(2020/05/18)
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- Process for synthesis of Oroxylin A
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Disclosed is a novel, simple, scalable and environment friendly process for the synthesis of Oroxylin A from Baicalin. Baicalin is esterified to obtain a methyl ester which is further selectively methylated to provide Oroxylin A glucuronide methyl ester which on de-glycosylation results in the formation of Oroxylin A.
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Page/Page column 4; 13
(2019/09/23)
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- Process for Preparing Oroxylin A
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A process for preparing oroxylin A includes: subjecting baicalin to a methylation reaction using a methylating reagent in the presence of a base to methylate the 6-hydroxyl group of baicalin, so as to form a methylated compound; and subjecting the methylated compound to a deglucuronidation reaction in the presence of an acid, so as to form oroxylin A.
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Paragraph 0033-0038
(2019/03/08)
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- Synthesis of oroxylin A starting from naturally abundant baicalin
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– A new approach to oroxylin A, a monomethylated trihydroxyflavone, is described. The starting material was baicalin, a representative naturally abundant flavonoid glucuronide. First, conditions for the cleavage of the glycosidic bond were established, using a mixture of water and conc. sulfuric acid (5:2) at 121 °C for 40 min. The hydrolysis was performed in a high-pressure steam sterilizer so that the temperature and reaction time were precisely controlled. Subsequent acetylation of the crude material furnished baicalein 6,7-diacetate on a preparative scale and in a reproducible manner. Next, the C-7 position was protected site-selectively with a methoxymethyl (MOM) group, taking advantage of an unexpected sequential migration of the two acetyl groups among the C-5, C-6, and C-7 positions under basic conditions. The removal of the two remaining acetyl groups followed by site-selective methylation of the C-6 position furnished 5-hydroxy-6-methoxy-7-methoxymethoxyflavone (oroxylin A C-7 MOM ether). Finally, by the deprotection of the MOM ether, oroxylin A was obtained in 6 total steps and 62% overall yield from baicalin.
- Fujita, Rie,Hanaya, Kengo,Higashibayashi, Shuhei,Sugai, Takeshi
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p. 1165 - 1174
(2019/07/31)
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- Method for synthesizing oroxylin A in which baicalin is used as an initiator for conveniently and efficiently synthesizing oroxylin by a chemical synthesis method
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Provided is a method for synthesizing oroxylin A, which utilizes baicalin as an initiator for conveniently and efficiently synthesizing oroxylin by a chemical synthesis method. The method for synthesizing oroxylin A comprises a methylation step for using baicalin as an initiator, and subjecting the initiator to a methylation reaction in an alkaline first reaction solution, so that a 6-hydroxyl group of the initiator is methylated to obtain an intermediate product, wherein the first reaction solution is composed of an inorganic base and a methylating agent; and a protecting group removal step for removing a carbohydrate group of the intermediate product in an acidic second reaction solution to form a hydroxyl group, thereby completing the synthesis of the oroxylin A.
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Paragraph 0026-0028
(2018/11/22)
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- Synthetic method for oroxylin A
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The invention provides a synthetic method for oroxylin A. According to the invention, baicalin is used as a starting material, and oroxylin A can be synthesized by using a simple and effective chemical synthesis method.
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Paragraph 0034; 0035; 0036; 0037
(2018/09/14)
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- Enzymatic production of oroxylin A and hispidulin using a liverwort flavone 6-O-methyltransferase
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Oroxylin A and hispidulin, compounds which are abundant in both Scutellaria and liverwort species, are important lead compounds for the treatment of ischemic cerebrovascular disease. Their enzymatic synthesis requires an O-methyltransferase able to interact with the related flavonoid's 6-OH group, but such an enzyme has yet to be identified in plants. Here, the gene encoding an O-methyltransferase (designated PaF6OMT) was isolated from the liverwort species Plagiochasma?appendiculatum. A test of alternative substrates revealed that its strongest preferences were baicalein and scutellarein, which were converted into, respectively, oroxylin A and hispidulin. Allowed a sufficient reaction time, the conversion rate of these two substrates was, respectively, 90% and 100%. PaF6OMT offers an enzymatic route to the synthesis of oroxylin A and hispidulin.
- Zhang, Yu-Ying,Xu, Rui-Xue,Gao, Shuai,Cheng, Ai-Xia
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p. 2619 - 2628
(2017/01/14)
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- Activities of Wogonin Analogs and Other Flavones against Flavobacterium columnare
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In our on-going pursuit to discover natural products and natural product-based compounds to control the bacterial species Flavobacterium columnare, which causes columnaris disease in channel catfish (Ictalurus punctatus), we synthesized flavone and chalcone analogs, and evaluated these compounds, along with flavonoids from natural sources, for their antibacterial activities against two isolates of F. columnare (ALM-00-173 and BioMed) using a rapid bioassay. The flavonoids chrysin (1a), 5,7-dihydroxy-4′-methoxyflavone (11), isorhamnetin (26), luteolin (27), and biochanin A (29), and chalcone derivative 8b showed strong antibacterial activities against F. columnare ALM-00-173 based on minimum inhibition concentration (MIC) results. Flavonoids 1a, 8, 11, 13 (5,4′-dihydroxy-7-methoxyflavone), 26, and 29 exhibited strong antibacterial activities against F. columnare BioMed based upon MIC results. The 24-h 50% inhibition concentration (IC50) results revealed that 27 and 29 were the most active compounds against F. columnare ALM-00-173 (IC50 of 7.5 and 8.5 mg/l, resp.), while 26 and 29 were the most toxic compound against F. columnare BioMed (IC50 of 9.2 and 3.5 mg/l, resp.). These IC50 results were lower than those obtained for wogonin against F. columnare ALM-00-173 and F. columnare BioMed (28.4 and 5.4 mg/l, resp.). However, based on MIC results, none of the compounds evaluated in this study were as active as wogonin (MIC 0.3 mg/l for each F. columnare isolate). Further modification of the wogonin structure to enhance antibacterial is of interest.
- Tan, Cheng-Xia,Schrader, Kevin K.,Khan, Ikhlas A.,Rimando, Agnes M.
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p. 259 - 272
(2015/10/19)
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- Oroxylin A analogs exhibited strong inhibitory activities against iNOS-mediated nitric oxide (NO) production
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A number of oroxylin A analogs were prepared and evaluated for their inhibitory activities against iNOS-mediated nitric oxide (NO) production from LPS-stimulated BV2 cells. The analogs were synthesized from purchased 2′-hydroxy-4,5,6-trimethoxyacetophenone and aldehydes in 3 steps. Among the tested compounds, several analogs (3b, 3c, 3d, 3f) exhibited strong inhibitory activities. Especially, the analog with 4-nitrophenyl group (3b) showed stronger inhibitory activity (IC50 = 4.73 μM) than that of wogonin (IC50 = 7.80 μM).
- Pham, Tuan-Ahn. N.,Che, Haiyan,Phan, Phuong-Thuy T.,Lee, Jae-Won,Kim, Sung-Soo,Park, Haeil
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p. 2534 - 2535
(2012/05/05)
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- Methods of synthesizing flavonoids and chalcones
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Simple and efficient total syntheses of flavonoids including baicalein, oroxylin A and wogonin are described herein. Simultaneous syntheses of oroxylin A and wogonin are also described.
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- Structure-activity relationships for α-glucosidase inhibition of baicalein, 5,6,7-trihydroxyflavone: The effect of A-ring substitution
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In order to estimate the effects of the A-ring hydroxyl group of baicalein (5,6,7-trihydroxyflavone, 1) on rat intestinal α-glucosidase inhibition, flavone, monohydroxyflavones, dihydroxyflavones, and methylated derivatives of 5,6,7-trihydroxyflavone were used for the structure-activity relationship (SAR) study. The importance of the 6-hydroxyl group of baicalein was validated for an exertion of the activity. And also, the tested flavones which lacked a hydroxyl substituent on any of positions 5, 6, or 7, showed no activity. Hence, the 5,6,7-trihydroxyflavone structure was concluded to be crucial for the potent inhibitory activity. In addition, an introduction of electron-withdrawing or electron-donating groups at position 8 of baicalein led to a dramatic decrease for activity, except for 8-fluoro-5,6,7-trihydroxyflavone, which carried a less bulky substituent on position 8. Hence, this result suggested that a sterically bulky substituent on C-8 of baicalein was detrimental for the activity regardless of its electronic nature. Through examining the inhibitory mechanism of baicalein against rat intestinal α-glucosidase, it was suggested to be a mixed type inhibition.
- Gao, Hong,Nishioka, Tetsuo,Kawabata, Jun,Kasai, Takanori
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p. 369 - 375
(2007/10/03)
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- Novel synthesis of flavonoids of Scutellaria baicalensis Georgi.
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A concise and efficient total synthesis of the flavonoids baicalein, oroxylin A and wogonin was described. Intramolecular oxidative cyclization followed by demethylation of chalcone 1, readily prepared from trimethoxyphenol, afforded, depending upon the controlled conditions, baicalein or oroxylin A in excellent yields. Demethylation of 1 yielded 3, which, by oxidation with I(2)/dimethyl sulfoxide (DMSO), was readily converted to oroxylin A and wogonin after column chromatography.
- Huang, Wen-Hsin,Chien, Pei-Yu,Yang, Ching-Huey,Lee, An-Rong
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p. 339 - 340
(2007/10/03)
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- Gastroprotective flavone/flavanone compounds with therapeutic effect on inflammatory bowel disease
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PCT No. PCT/KR97/00144 Sec. 371 Date Jan. 14, 1999 Sec. 102(e) Date Jan. 14, 1999 PCT Filed Jul. 25, 1997 PCT Pub. No. WO98/04541 PCT Pub. Date Feb. 5, 1998The present invention relates to novel flavone/flavanone compounds or their pharmaceutically acceptable salts and process for preparation thereof for protecting gastrointestinal tracts against gastritis, ulcers and inflammatory bowel disease.
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- O-methylation of flavonoids by cell-free extracts of calamondin orange
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Cell-free extracts of calamondin orange (Citrus mitis) catalysed the O-methylation of almost all hydroxyls of a number of flavonoids, indicating the existence in citrus tissues of ortho, meta, para and 3-O-methyltransferases. The latter, hitherto unreported enzyme, catalysed the formation of 3-O-methyl ethers of galangin and quercetin. The stepwise O-methylation of a number of compounds, especially quercetin and quercetagetin, tends to suggest a coordinated sequence of O-methylations on the surface of a multienzyme complex. The methyl acceptor abilities of the flavonoid substrates used are discussed in relation to their hydroxyl substitution patterns and their negative electron density distribution.
- Brunet, Gunter,Ibrahim, Ragai K.
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p. 741 - 746
(2007/10/02)
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