Anthraquinones from Polygonum cuspidatum as tyrosinase inhibitors for dermal use

Four anthraquinones, physcion (1), emodin (2), citreorosein (3) and anthraglycoside B (6), and two stilbenes, resveratrol (4), and piceid (5), were isolated previously from the root of Polygonum cuspidatum. These bioactive compounds were examined for their antityrosinase potency. No antityrosinase activity was detected with treatment using stilbenes. On the other hand, the anthraquinones showed moderate to strong inhibition of tyrosinase. Physcion exhibited the most potent tyrosinase inhibition among the four anthraquinones examined, which was comparable to kojic acid. The ability of anthraquinones to permeate the skin was also examined. Based on the same thermodynamic activity, physcion showed a higher permeation compared with emodin (48-fold), suggesting it as a potent candidate for dermal use. As naturally occurring tyrosinase inhibitors, anthraquinones from P. cuspidatum may be useful as skin-whitening agents to inhibit tyrosinase for dermal use.