151133-79-8Relevant articles and documents
Nitrosation and analysis of amino acid derivatives by isocratic HPLC
Ulusoy, Songül,Ulusoy, Halil Ibrahim,Pleissner, Daniel,Eriksen, Niels Thomas
, p. 13120 - 13128 (2016/02/12)
The objective of this study was to characterize the nitrosation of the classical amino acids by N2O3. Nitrosation of amino acids results in the formation of mainly α-hydroxy-acids that are suitable for isocratic HPLC analysis and subsequent quantification of amino acids in biological samples. The method is particularly suitable for detection of amino acids in e.g. fermentation media as the α-hydroxy-acids can be quantified in parallel to a variety of other organic substrates and products. The amino acids were transformed into their corresponding α-hydroxy-acids in acidic KNO2 solutions. The reactions were terminated by NaOH addition and the α-hydroxy-acids separated by isocratic HPLC and quantified by refractive index or UV absorption detection. Nitrosation of 18 of the classical amino acids; glycine, l-alanine, l-valine, l-leucine, l-isoleucine, l-methionine, l-serine, l-threonine, l-asparagine, l-glutamine, l-aspartic acid, l-glutamic acid, l-proline, l-cysteine, l-phenylalanine, l-lysine, l-tyrosine, and l-tryptophane formed detectable nitrosation products. l-Lysine, however, needed incubation in 96 mM formic acid to produce a detectable product, while l-phenylalanine had to be incubated in 120 mM HNO3 and 100 mM HCl. Optimal reaction conditions for most amino acids included 40 min of incubation of up to 5 g L-1 amino acid in 160 mM KNO2 in 100 mM HCl at 45 °C to maximize product yields.
Three bioactive cyclic dipeptides from the Bacillus sp. N strain associated with entomopathogenic nematode
Nishanth, Sasidharan Kumar,Nambisan, Bala,Dileep
, p. 59 - 69 (2014/05/06)
In continuation of our search for new bioactive secondary metabolites from Bacillus cereus associated with entomopathogenic nematode (EPN), three cyclic dipeptides (CDPs), cyclo(l-Leu-d-Arg) (1), cyclo(2-hydroxy-Pro-l-Leu) (2), and cyclo(l-Val-l-Pro) (3) were purified from the ethyl acetate extract of B. cereus. The chemical structure of the compounds was identified by 1D, 2D NMR and HR-ESI-MS. Cyclo(l-Leu-d-Arg) recorded best antifungal activity and the highest activity was recorded against Cryptococcus neoformans (1 μg/mL), which is better than the standard antifungal agent amphotericin B. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was used for finding cell proliferation inhibition and cyclo(l-Leu-d-Arg) recorded significant activity against breast cancer cell line (MDAM-B231) (IC50 value: 25 μM) and the three cyclic dipeptides recorded no toxicity against normal human cell (fore skin (FS) normal fibroblast) up to 50 μM except cyclo(l-Val-l-Pro). Cyclo(l-Leu-d-Arg) induced significant morphological changes and DNA fragmentation associated with apoptosis in MDAM-B231 cells by acridine orange/ethidium bromide staining and flow cytometry analysis. Out of three cyclic dipeptides tested only cyclo(2-hydroxy-Pro-l-Leu) recorded significant antioxidant activity. The hydroxyl radical scavenging activity of cyclo(2-hydroxy-Pro-l-Leu) is greater than BHA, the standard antioxidant agent. Cyclo(l-Leu-d-Arg) was isolated for the first time from a natural source with a d-arginine residue. To the best of our knowledge, this is the first time that the bioactivity of the isolated cyclic dipeptides is reported against medically important fungi and cancer cells. This study is a significant contribution to the knowledge of cyclo(l-Leu-d-Arg) from B. cereus as potential sources of new drugs in the pharmacological industry, especially as potent antifungal and anticancer agent.
