Abstract
Two flavonols, quercetin (1) and quercitrin (2), were isolated from the leaves of Zanthoxylum piperitum. Their structures were established by UV, one- and two-dimensional NMR, and mass spectroscopic methods. Quercetin showed significant inhibition against mushroom tyrosinase with an IC50 value of 3.8 microg/ml, and appeared to inhibit the polyphenol oxidase activity of tyrosinase in a competitive manner (Ki = 10 +/- 0.20 microM) when L-tyrosine was used as a substrate, although it did not inhibit the melanin production of Streptomyces bikiniensis.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Agaricales / enzymology
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Catechol Oxidase / antagonists & inhibitors
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Enzyme Inhibitors / isolation & purification*
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Enzyme Inhibitors / pharmacology
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Flavonols / isolation & purification
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Flavonols / pharmacology
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Fungal Proteins
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Inhibitory Concentration 50
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Kinetics
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Magnetic Resonance Spectroscopy
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Mass Spectrometry
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Melanins / biosynthesis
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Molecular Structure
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Monophenol Monooxygenase / antagonists & inhibitors*
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Plant Leaves / enzymology
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Quercetin / analogs & derivatives*
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Quercetin / isolation & purification
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Quercetin / pharmacology
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Zanthoxylum / enzymology*
Substances
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Enzyme Inhibitors
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Flavonols
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Fungal Proteins
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Melanins
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quercitrin
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Quercetin
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Catechol Oxidase
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Monophenol Monooxygenase