Hyun Sook Kyung, Lee Won-Hee, Jeong Da Mi, Kim Youngsoo, Choi Jae Sue
Division of Food Science and Biotechnology, Pukyong National University, Busan 608-737, Korea.
Biol Pharm Bull. 2008 Jan;31(1):154-8. doi: 10.1248/bpb.31.154.
Previously, it was reported that some prenylated flavonoids contained in the dichloromethane fraction of the ethanolic extract of Sophora flavescens, such as kuraridin, sophoraflavanone G, kurarinone, and kushenol F, are tyrosinase inhibitors; however, based on the level of these inhibitors in the extract, its inhibitory effect on tyrosinase activity was higher than expected. This has led us to further investigate other possible constituents that may contribute to the extract's strong inhibitory activity. The results of this study indicate that kurarinol (1), kuraridinol (2), and trifolirhizin (3), from the ethyl acetate fraction of Sophora extract, can inhibit tyrosinase activity. Compared with kojic acid (16.22+/-1.71 microM), compounds 1-3 possessed potent tyrosinase inhibitory activity with IC(50) values of 8.60+/-0.51, 0.88+/-0.06, and 506.77+/-4.94 microM, respectively. These three compounds were further tested for their inhibitory effects on melanogenesis. In cultured B16 melanoma cells, 1-3 markedly inhibited (>50%) melanin synthesis at 50 microM. This is the first study indicating that 1-3 exert varying degrees of inhibition on tyrosinase-dependent melanin biosynthesis, and therefore, are candidates as skin-whitening agents.
此前有报道称，苦参乙醇提取物二氯甲烷部分所含的一些异戊烯基黄酮，如苦参啶、苦参黄酮G、苦参酮和苦参醇F，是酪氨酸酶抑制剂；然而，基于提取物中这些抑制剂的含量，其对酪氨酸酶活性的抑制作用高于预期。这促使我们进一步研究其他可能对提取物强大抑制活性有贡献的成分。本研究结果表明，苦参提取物乙酸乙酯部分的苦参醇（1）、苦参啶醇（2）和三叶豆紫檀苷（3）可抑制酪氨酸酶活性。与曲酸（16.22±1.71微摩尔）相比，化合物1 - 3具有较强的酪氨酸酶抑制活性，IC50值分别为8.60±0.51、0.88±0.06和506.77±4.94微摩尔。进一步测试了这三种化合物对黑色素生成的抑制作用。在培养的B16黑色素瘤细胞中，1 - 3在50微摩尔时显著抑制（>50%）黑色素合成。这是第一项表明1 - 3对酪氨酸酶依赖性黑色素生物合成有不同程度抑制作用的研究，因此，它们有望成为美白剂。
