Anti-Oxidant and Anti-Tyrosinase natural products of nymphaea stellata
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Date
2009
Authors
Gayani, Pathirage Anusha
Journal Title
Journal ISSN
Volume Title
Publisher
University of Peradeniya
Abstract
In search of anti-oxidants and anti-tyrosinase natural sources, the anti-oxidant and anti- tyrosinase activities of Nymphaea stellata stamens (Manel, Nilmanel, Nymphaeaceae) were identified. Air-dried stamens of N. stellata were sequentially extracted into hexane, ethyl acetate and ethanol. Bio-assay guided fractionation of the sequential ethanol extract by chromatography followed by recrystallization afforded six compounds. Structure elucidation of compound 6 was achieved by '<chemical formulaa> and DEPT spectroscopic techniques. The structure of compound 6 was tentatively established as cyanidin derivative, which is cyanidin 3-O-(2"-O-galloyl-β-galactopyranoside) and exhibited very good anti-oxidant activity (<chemical formulaa> = 5.44 ± 1.02 ppm).
<chemical structure>
Compound 6, cyanidin 3-O-(2"-O-galloyl-β-galactopyranoside)
Anti-oxidant activity of extracts and fractions were evaluated using in vitro 1,1- diphenyl-2-picrylhydrazyl (DPPH) assay. The sequential ethanol extract of N. stellata demonstrated the highest anti-oxidant activity (<chemical formular> =12.37 ±0.25 ppm). All extracts were inferior to that of L-ascorbic acid (<chemical formular>) =3.61± 0.05 ppm). Among the chromatography fractions, F1 to F13 obtained from the sequential ethanol extract, the fraction F11 possessed the highest anti-oxidant activity (<chemical formular> =5.97 ± 0.23 ppm). Fraction F14 isolated from total ethanol extract also possessed good activity (<chemical formular> =6.94 ± 0.37 ppm). Anti-tyrosinase activity of extracts of N. stellata was evaluated using 3,4-dihydroxy-L- phenylalanine (L-DOPA) as a substrate and the sequential ethanol extract demonstrated the highest anti-tyrosinase activity (<chemical formular>=378.58 ± 48.62 ppm). All extracts were inferior to those of L-ascorbic acid (<chemical formular>=74.17 +5.46 ppm). Polyphenol content of stamen extracts of total ethanol and sequential extracts of hexane, ethyl acetate and ethanol was determined by Folin-Ciocalteu method using gallic acid as a standard. Sequential ethanol extract showed the highest polyphenol content (254.55 ± 3.99 GAE mg/g). The Highest anti-oxidant and anti-tyrosinase activity of the sequential ethanol extract may be correlated to the phenolic content of this extract. The activity data further suggest that sequential ethanol extract could be developed as a natural ingredient for cosmetic products such as natural skin-whitening agent. However, the toxicity of these extracts needs to be evaluated before use in such products.
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Keywords
Chemical sciences , Analytical chemistry , Natural products