Inhibition of melanogensis by a novel origanoside from Origanum vulgare

BackgroundNatural and synthetic substances are becoming increasingly utilized as tyrosinase inhibitors of depigmentation and developed cosmetics industry. However, few have been employed as skin-whitening agents, primarily because of numerous safety concerns.ObjectiveA novel compound was found, and then its safe concentrations and inhibition effect of hyperpigmentation by the regulation of the tyrosinase family of proteins were examined.MethodsA novel phenolic glucoside, origanoside (1), was isolated from Origanum vulgare. The structure of the origanoside (1) was established on the basis of spectral evidence and the safe concentrations were determined by MTT assay. Skin-whitening capacity in skin fibroblast Hs68 and melanoma B16 cells and in vivo animal test for origanoside (1) were investigated.ResultsOriganoside (1) is non-toxic in concentrations of 0–100 μg/ml in both cells. The ability of origanoside (1) to inhibit cellular tyrosinase and DOPA oxidase in B16 cells was investigated. Origanoside (1) significantly reduced expressions of microphthalmia-associated transcription factor (MITF), tyrosinase and tyrosinase-related proteins 2 (TRP-2) in vitro and in vivo, suggesting that origanoside (1) is responsible for the antimelanogenic effect. Smearing origanoside (1)-gel samples on 12 mice for 10 days increased L*, reduced a* and erythema-melanin (E/M), and b* was almost unchanged compared with those of samples and untreated groups, indicating that the skin lightened.ConclusionExperimental data demonstrate that origanoside (1) causes depigmentation and may be useful for novel food additives and skin-whitening cosmetics.