Methyl p-coumarate, a melanin formation inhibitor in B16 mouse melanoma cells
摘要:
p-Coumaric acid (4-hydroxycinnamic acid) and methyl p-coumarate (methyl 4-hydroxycinnamate) inhibit the oxidation Of L-tyrosine catalyzed by mushroom tyrosinase. However, both were oxidized as monophenol substrate analogues at an extremely slow rate. This oxidation was significantly accelerated as soon as catalytic amounts (0.01 mM) Of L-3,4-dihydroxyphenylalanine (L-DOPA) became available as a co-factor. Methyl p-coumarate significantly suppressed the melanin formation in B16 mouse melanoma cells, whereas p-coumaric acid did not show this activity. (C) 2004 Elsevier Ltd. All rights reserved.
Formation of Strecker Aldehydes from Polyphenol-Derived Quinones and α-Amino Acids in a Nonenzymic Model System
作者:George P. Rizzi
DOI:10.1021/jf052781z
日期:2006.3.1
vegetables contain naturally occurring polyphenolic compounds that can undergo enzyme-catalyzed oxidation during food preparation. Many of these compounds contain catechol (1,2-dihydroxybenzene) moieties that may be transformed into o-quinone derivatives by polyphenoloxidases and molecular oxygen. Secondary reactions of the o-quinones include the Strecker degradation of ambient amino acids to form flavor-important
Degradation of Cyanidin 3-Glucoside by Caffeic Acid <i>o</i>-Quinone. Determination of the Stoichiometry and Characterization of the Degradation Products
formation of brown polymers. The degradationproducts were isolated by gel filtration on Sephadex G-25. The UV-vis spectra and chemical analysis (acidic hydrolysis) of the degradationproducts suggest that they resulted from the condensation of caffeic acid and Cy 3-glc. HPLC analysis showed that the partial purified fraction contained a mixture of complex condensation products.