Shin N H, Ryu S Y, Choi E J, Kang S H, Chang I M, Min K R, Kim Y
College of Pharmacy, Chungbuk National University, Cheongju, Korea.
Biochem Biophys Res Commun. 1998 Feb 24;243(3):801-3. doi: 10.1006/bbrc.1998.8169.
Oxyresveratrol (2,3',4,5'-tetrahydroxystilbene), a naturally occurring compound particularly found in Morus alba L., exhibited a potent inhibitory effect on dopa oxidase activity of tyrosinase which catalyzes rate-limiting steps of melanin biosynthesis. Oxyresveratrol with 0.3 to 5 microM exhibited potent and dose-dependent inhibitions (25 to 84%) on the enzyme activity, where 50% of inhibition was shown at the concentration of about 1 microM. Oxyresveratrol seemed to inhibit the dopa oxidase activity of tyrosinase via a noncompetitive manner (Ki = 9.1 x 10(-7) M) when L-dopa was used as a substrate. Oxyresveratrol exhibited about a 150-fold more potent inhibitory effect than resveratrol (3,4',5-trihydroxystilbene). The more hydroxy groups of the hydroxystilbenes are methylated to be methoxy groups, while the less inhibitory effects on the enzyme activity were exhibited. The results indicate that both the number and positions of hydroxy groups in oxyresveratrol seem to play a critical role in exerting the inhibitory effect on dopa oxidase activity of mushroom tyrosinase.
氧化白藜芦醇（2,3',4,5'-四羟基茋）是一种天然存在的化合物，尤其在桑白皮中被发现，它对催化黑色素生物合成限速步骤的酪氨酸酶的多巴氧化酶活性表现出强烈的抑制作用。浓度为0.3至5微摩尔的氧化白藜芦醇对该酶活性表现出强烈的剂量依赖性抑制（25%至84%），在约1微摩尔的浓度下显示出50%的抑制率。当以L-多巴作为底物时，氧化白藜芦醇似乎通过非竞争性方式抑制酪氨酸酶的多巴氧化酶活性（Ki = 9.1×10⁻⁷ M）。氧化白藜芦醇的抑制作用比白藜芦醇（3,4',5-三羟基茋）强约150倍。羟基茋的羟基甲基化程度越高，形成甲氧基的数量越多，对酶活性的抑制作用就越弱。结果表明，氧化白藜芦醇中羟基的数量和位置似乎在对蘑菇酪氨酸酶的多巴氧化酶活性发挥抑制作用中起着关键作用。
