In this study, 15 wine cakes from various sources were collected for the investigation of whitening and moisturizing effects. The fatty acid and free amino acid contents of the wine cakes were analyzed. The results showed that flattened yellow wine cake had the highest free amino acid contents (630 mg/100 g) among all the wine cakes tested. In addition, the fatty acid content of the wine cakes was higher than that of Japanese sake wine. Since the fatty acids and amino acids of wine cake are similar to the natural moisturizing factors and the intercellular lipids in the human epidermis, the wine cakes could be applied as cosmetic humectants.
The ethanolic extracts of wine cakes were subjected to tests for the inhibition zones of tyrosinase, the inhibition rates on tyrosinase
activity, and inhibition of DOPA quinone synthesis via B16 melanoma cell. The inhibition zones of tyrosinase caused by grain sorghum wine cakes and yellow wine cakes were larger than that of arbutin. Reduction of the inhibition rate on tyrosinase activity was in the following order: dry grain sorghum wine cake, flattened yellow wine cake, wet grain sorghum wine cake, dry yellow wine cake and wet yellow wine cake. Moreover, in the tests for inhibition of DOPA quinone synthesis, higher inhibitions were shown for dry grain sorghum wine cake by 1.03-fold, wet grain sorghum wine cake by 0.74-fold, dry yellow wine cake by 0.62-fold, wet yellow wine cake by 0.94-fold, and sake wine cake by 0.78-fold, when compared with arbutin. Our results of the three in vitro inhibition tests for tyrosinase activity indicated that grain sorghum wine cakes and yellow wine cakes can be developed for use as skin-whitening agents and humectants.