In this study, the effect of purified quercetin-3-O-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranosid (QCGG) on melanogenesis was investigated. QCGG was isolated from the calyx of a traditional Korean medicinal herb, Persimmon (Diospyros kaki). The hypopigmentation effects of QCGG were determined by examination of cellular melanin contents, tyrosinase activity assay, cAMP assay, and Western blotting of α-MSH-stimulated B16F10 mouse melanoma cells. Our results showed that QCGG inhibited both melanin synthesis and tyrosinase activity in a concentration-dependent manner as well as significantly reduced the expression of melanogenic proteins such as microphthalmia-associated transcription factor (MITF), tyrosinase-related protein-1, tyrosinase-related protein-2, and tyrosinase. Moreover, QCGG inhibited intracellular cAMP levels, cAMP response element-binding protein (CREB), and p38 MAPK expression in α-MSH-stimulated B16F10 cells. Taken together, the suppressive effects of QCGG on melanogenesis may involve down-regulation of MITF and its downstream signaling pathway via phosphorylation of p38 MAPK and CREB along with reduced cAMP levels. These results indicate that QCGG reduced melanin synthesis by reducing expression of tyrosine and tyrosine-related proteins via extracellular signal-related protein kinase (ERK) activation, followed by down-regulation of CREB, p38, and MITF.

Many diseases are associated with oxidative stress caused by reactive oxygen species and free radicals generated in living cells. This study deals with finding naturally occurring antioxidants of plant origin. The study investigated the phytochemistry, antioxidant and free radical scavenging potential of ethanolic leaf extract of Adhatoda vasica (ELEAV) using different antioxidant models. The phytochemical analysis of ELEAV revealed the presence of alkaloids, flavonoids, terpenoids, saponins, phenols and steroids. ELEAV also showed an antioxidant capacity, with inhibition of the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical by 69.23%. ELEAV had potent inhibitory effects on scavenging nitric oxide, superoxide and hydroxyl radicals, by 65.24%, 61.54% and 61.24%, respectively. Moreover, ELEAV displayed a concentration-dependent reducing power activity and potent inhibitory effects on ferric ion-induced lipid peroxidation (68.26%) in bovine brain extract. These findings confirm the biological efficacy of A. vasica as a potential source of natural antioxidants.