Monosaccharide Composition and Dynamic Mechanism Analysis of Inhibiting Tyrosinase of Bletilla striata Polysaccharides
The content of Bletilla striata polysaccharides was determined by the phenol-sulfuric acid method,the monosaccharide composition was measured by the ion chromatography method,and the dynamic param-eters of inhibiting tyrosinase activity of Bletilla striata polysaccharides were obtained by adopting the enzymoly-sis assay.The results showed that the content of Bletilla striata polysaccharides extracted by the multi-enzyme method was(51.97±1.52)%.By employing ion chromatography,the study found that the monosaccharide com-position of Bletilla striata polysaccharides included seven kinds:Rha,Ara,Gal,Glc,Man,GAL-UA and GLc-UA,and the proportions of monosaccharides were 0.17%,0.36%,1.86%,41.81%,54.21%,0.71%,and 0.88%respectively.In vitro,Bletilla striata polysaccharides exerted an inhibitory effect on tyrosinase's activity,with the IC50 of Bletilla striata polysaccharides being 59.31 mg/mL.Additionally,Bletilla striata poly-saccharides could reduce the initial reaction speed of tyrosinase,which indicated that Bletilla striata polysac-charides had a delayed effect on the catalysis of tyrosinase.Meanwhile,with the increasing mass concentration of Bletilla striata polysaccharides,they had a stronger inhibition effect on tyrosinase's activity,with the char-acteristics of dose-dependency and reversibility.The Lineweaver-Burk double-reciprocal curve showed that with the rising mass concentration of Bletilla striata polysaccharides,the value of the Michaelis constant Km gradually increased,while Vmax gradually decreased.This indicated that the inhibitory effect of Bletilla striata polysaccharides on tyrosinase was a type of non-competitive and competitive mixed inhibition.
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