Evaluation of natural products as potential cosmetic agents with tyrosinase inhibition activity

Skin whitening effects of a library of plant derived natural products were evaluated for their potential as new cosmetic agents. Specifically, 480 compounds with structurally diverse scaffolds and decoration patterns were screened for their anti-hyperpigmentation properties. The ability of the compounds to inhibit the oxidation of L-DOPA to dopaquinone and subsequently to dopachrome by the enzyme tyrosinase in a cell-free system was examined. The produced amount of dopachrome was measured at 475nm, and kojic acid was used as positive control. Four compounds were found to be very active (IC₅₀<50µg/ml), 3 compounds showed a moderate activity (75µg/ml>IC₅₀>50µg/ml), and 10 compounds were found to be weak inhibitors (150µg/ml>IC₅₀>75µg/ml). Esculetin was the most potent inhibitor of tyrosinase. Its IC₅₀ value was 3.7µM which was lower than that of kojic acid (IC₅₀=11.9µM). On the basis of this screening an extract library derived from approx. 1800 plant species of the worldwide flora has been established.