An inhibitory effect of magnesium L-ascorbyl-2-phosphate (VC-PMG, a stable derivative of ascorbic acid) on melanogenesis has been described. Furthermore, glabridin in licorice is known to have inhibitory effects on melanogenesis and widely used for raw materials for depigmenting agents.

The purposes of this study are to provide objective data by measuring the visual clinical effects of VC-PMG with the colorimeter and to promote the development of de-pigmenting agents.

20 volunteers joined the study. With an artificial UVB irradiation, eight tanned areas were made on the inner side of the forearm. During two months, each tanned area was treated with five whitening cosmetics with 3% VC-PMG and increasing concentration of licorice from 0% to 3%. Darkness degree of each area was measured weekly by the colorimeter and the visual assessment.

For all cosmetics, whitening effect was measured by colorimeter and visual as-sessment. The cosmetic containing VC-PMG 3% and licorice 1% had more whitening effect than any other cosmetics of different concentrations. Moreover, VC-PMG 3% alone also had whitening effect in some volunteers.

VC-PMG was clinically found to have whitening effect.