广西瑶族藤茶化学成份的研究

从广西瑶族藤茶,即显齿蛇葡萄(Ampelopsis grossedentata)中提取分离出两种黄酮类化合物,经化学和光谱解析,鉴定为杨梅树皮素(Myricetin,C_(15)H_(10)O_8,结晶Ⅰ),双氢杨梅树皮素(DL-dihydromyricetin,C_(15)H_(12)O_8,结晶Ⅱ),其中杨梅树皮素为首次报道从该植物中获得。     

Molecular inhibitory mechanism of dihydromyricetin on mushroom tyrosinase

Tyrosinase is the rate-limiting enzyme for controlling the production of melanin in the human body, and overproduction of melanin can lead to a variety of skin disorders. In this paper, the inhibitory kinetics of Dihydromyricetin (DHM) on tyrosinase and their binding mechanism were determined using spectroscopy, molecular docking, antioxidant assays, and chromatography. The spectroscopic results indicate that DHM reversibly inhibits tyrosinase in a mixed-type manner through a multiphase kinetic process with the IC₅₀ of 849.88 μM. It is shown that DHM has a strong ability to quench the intrinsic fluorescence of tyrosinase mainly through a static quenching procedure, suggesting that a stable DHM–tyrosinase complex is generated. Molecular docking results suggest that the dominant conformation of DHM does not directly bind to the active site of tyrosinase. Moreover, the antioxidant assays demonstrate that DHM has powerful antioxidant and reducing capacity but does not have the ability to reduce dopachrome to L-DOPA. Interestingly, the results of spectroscopy and chromatography indicate that DHM is a substrate of tyrosinase but not a suicide substrate. The possible inhibitory mechanism is proposed, which will be helpful to design and search for tyrosinase inhibitors.