Abstract—

Brassica campestris L. is the important oil-bearing crop in China. Rapeseed cake is the main byproduct of rapeseed oil extraction. As the main active ingredient in rapeseed cake, sinapine has several important biological activities. Therefore, the inhibitory activity of sinapine on tyrosinase in vitro and its free radical-scavenging rate were determined. Tyrosinase activity in A-375 human melanocytes was also investigated and the effects of sinapine on the melanin content and its antioxidant effects on melanin biosynthesis were studied. The results showed that sinapine had significant antioxidant activity. Sinapine significantly inhibited A-375 human melanocytes in a dose-dependent manner. Sinapine inhibited melanin synthesis in A-375 cells by downregulating the mRNA and protein expression of TRP-1, TRP-2, and MITF factors. The results showed that rapeseed cake sinapine inhibited melanin production and could be used as a potential active ingredient in the development of whitening agents.