The Screening,Structural Identification And Inhibition Mechanism,Research Of Xanthine Oxidase In Smilax China L.

Gout is a kind of common metabolic diseases.There is a positive correlation between the formation of gout and level of xanthine oxidase?XO?in Vivo.Therefore,XO Inhibitor become the important target for treatment and prevention of Gout.This experiment aims at the inhibitory effect and mechanism of Smilax china L.on xanthine oxidase.The rhizomes of Smilax china L.were extracted with 90%ethanol then extracted with petroleum ether,chloroform,ethyl acetate and butyl alcohol one after another.Screened out the most effective part and its chemical structures were identified.The inhibitory effect and mechanism of monomers on xanthine oxidase were measured.?1?Ethyl acetate extract exhibits the best inhibitory effect on XO and the inhibition type is competitive.?2?HPLC and HPLC-MS analysis showed that the two substances in the ethyl acetate layer were Quercetin-3-O-rhamoside.and chlorogenic acid.?3?Quercetin-3-O-rhamoside competitively inhibit XO and the IC₅₀ is 99.216?g/mL.?4?The inhibition of chlorogenic acid on XO is noncompetitive and the IC50 is99.473?g/mL.?5?Fluorescence quenching mechanism of Quercetin-3-O-rhamoside with XO was a static quenching procedure.The interaction between Quercetin-3-O-rhamoside and XO is an exothermic reaction and there is only one binding site.A slight blue shift suggesting that Quercetin-3-O-rhamoside bound to XO and induced the increase in hydrophobicity around Tyr residue.A slight red shift suggested the decrease in hydrophobicity around Trp residue.Quercetin-3-O-rhamoside caused the rearrangement of the polypeptide carbonyl hydrogen bonding network,the major conformation of XO was changed.CD spectroscopy showed contents of?-helix increased,?-sheet and random coil decreased.?6?Fluorescence quenching mechanism of chlorogenic acid with XO was a static quenching procedure.There is only one binding site The interaction between chlorogenic acid and XO.Chlorogenic acid induced the increase in?-helix and the decrease in?-turn and random coil.Polarity was redused and hydrophobicity was increased around Tyr residue.Smilax china L.has good XO inhibitory activity,and it can be one of the raw materials for natural xanthine oxidase inhibitors.