Tyrosinase is a key enzyme in the production of melanins. Phytochemical studies of a Glycyrrhiza uralensis extract were performed by measuring the tyrosinase and melanin synthesis inhibitory activity. Glycyrrhisoflavone and glyasperin C were identified as tyrosinase inhibitors for the first time. Glyasperin C showed a stronger tyrosinase inhibitory activity (IC (50) = 0.13 +/- 0.01 microg/mL) than glabridin (IC (50) = 0.25 +/- 0.01 microg/mL) and a moderate inhibition of melanin production (17.65 +/- 8.8 % at 5 microg/mL). Glycyrrhisoflavone showed a strong melanin synthesis inhibitory activity (63.73 +/- 6.8 % inhibition at 5 microg/mL). These results suggest that glyasperin C and glycyrrhisoflavone could be promising candidates in the design of skin-whitening agents.

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In this report, we have demonstrated that deoxypodophyllotoxin from Anthriscus sylvestris (L.) Hoffm decreases UV-induced skin pigmentation of brown guinea pigs. Deoxypodophyllotoxin (0.05 % in propylene glycol: ethanol: water = 5 : 3:2) was topically applied twice daily for two weeks to dorsal skin of brown guinea pigs that were exposed to UV irradiation using a solar simulator. Visual inspection and Fontana-Masson staining both demonstrated that deoxypodophyllotoxin reduced skin pigmentation and total epidermal melanin when compared to that of vehicle-treated areas, suggesting that deoxypodophyllotoxin maybe applicable to treat hyperpigmentation.

Ten new polyhydroxyolean-12-ene pentacyclic triterpenoidal saponins, named rogchaponins 1-10, were isolated from the methanolic extract of the roots of Camellia sinensis by a series of chromatographic methods (silica gel flash column and C18 MPLC followed by C18 HPLC). Their structures were established by 1D and 2D-NMR techniques along with IR and HR-TOF-MS. Rogchaponins R4 ( 4) and R5 (5) showed inhibitory activities against yeast alcohol dehydrogenase (ADH) with IC (50) values of 16.1 ± 3.2 and 15.4 ± 3.3 µM, respectively. A 4-methylpyrazole positive control exhibited an IC (50) of 2750 ± 50 µM. However, the saponins showed no inhibitory activity against yeast aldehyde dehydrogenase (ALDH).