Melanin Biosynthesis Inhibitory and Antioxidant Activities of Quercetin-3′-0-jff-D-glucoside Isolated from Allium cepa

In the course of searching for new whitening agents, we have found that the methanol extract of dried skin of Allium cepa shows potent melanin biosynthesis inhibitory activity in B16 melanoma cells. Bioassay-guided fractionation led to the isolation of quercetin-3′-0-8- D-glucoside (1) from the methanol extract of dried skin of A. cepa, which inhibited melanin formation in B16 melanoma cells with an IC₅₀value of 38.8 im and mushroom tyrosinase with an IC₅₀value of 6.5 jiM using L-tyrosine and 48.5 im using L-dihydroxyphenylalanine as substrates, respectively. In addition, the antioxidant activity of 1 was evaluated in the oxygen radical absorbance capacity assay; it showed 3.04 imol Trolox equivalents/mmol. 1 was shown to be a promising ingredient that could be useful for treating hyperpigmentation and for protecting against oxidative stress.