| In recent years, the incidence of gout and hyperuricemia are rising. Xanthine Oxidase(EC 1.2.3.2) is an important enzyme in the uric acid metabolism, which can catalyzes hypoxanthine and xanthine produce to be uric acid. The content of uric acid will be reduced when xanthine oxidase activity is inhibited. The main kind of drugs for treating gout and hyperuricemia is the inhibitor of xanthine oxidase. Allopurinol is mostly used in clinic, but it has many side effects. So, finding out the new kind of xanthine oxidase inhibitor is very significant. Chinese herbal medicine is plentiful in our coutry and has a long history of application. So, the screening of new XO inhibitor from Chinese herbal medicine can provide the theoretical basement for the development of XO targeting anti-gout drugs and functional foods.In this paper, 17 kinds of Chinese herbal medicines were selected. The vitro xanthine oxidase inhibitory activity of their water extracts and alcohol extracts were studied. Six kinds of water extract and six kinds of alcohol extract were elected from Chinese herbal medicines. The inhibitory mechanism of extract on XO was studied. Then, The inhibition kinetics of active ingredient was analyzed.The screening model of the XO inhibitor was established. It was based on the method of spectrophotography. The wave length was 295 nm.In this paper, the vitro xanthine oxidase inhibitory activity of the water extract of 17 kinds from Chinese herbal medicines were analyzed. The results showed that, 11 kinds of Chinese herbal medicine water extract(5 mg/mL)had the inhibitory activity on xanthine oxidase. The water extracts from cordyceps militaris, kudzu, hawthorn, chrysanthemum, cattail pollen, lotus leaf, notoginseng, terminalia chebula had good inhibitory effect.The xanthine oxidase inhibitory activity of alcohol extracts of 17 kinds of Chinese herbal medicine was evaluated under the same condition. The results showed that, 14 kinds of Chinese herbal medicine water extract(5 mg/mL) had the inhibitory activity on xanthine oxidase.The inhibition mechanism and type of the water extract from terminalia chebula, cordyceps militaris, kudzu, hawthorn, lotus leaf, notoginseng had been determined. The results showed that, the IC50 of the water extract from terminalia chebula, cordyceps militaris, kudzu of were 3.87 mg/mL, 6.45 mg/mL and 5.54 mg/mL. The water extracts of hawthorn, lotus leaf and notoginseng were belong to moderate xanthine oxidase inhibitors and the XO inhibitory rate below 50%. The inhibition type of the six water extract on XO was liner competitive inhibition. The Ki of the extract of terminalia chebula, cordyceps militaris and kudzu aqueous were 1.96 mg/mL, 2.61 mg/mL and 2.17 mg/mL. The Ki of the extract of lotus leaf, notoginseng and hawthorn aqueous were 52.48 mg/mL, 39.8 mg/mL and 50.9 mg/mL.The inhibition mechanism and type of terminalia chebula, cordyceps militaris, kudzu, hawthorn, chrysanthemum morofolium ramat, ginkgo leaf on inhibition and inhibition types were analyzed. The results showed that, The inhibition type of the terminalia chebula alcohol extract Hawthorn alcohol alcohol extract were belong to the anti-competitive inhibition, the IC50 were 5.37 mg/mL and 5.23 mg/mL, and the Ki were 3.43 mg/mL and 4.03 mg/mL. The inhibition type of the Cordyceps alcohol extract, Kudzu alcohol extract and Chrysanthemum morofolium ramat alcohol extract were belong to the competitive inhibition, the IC50 were 2.67 mg/mL, 6.36 mg/mL and 7.41 mg/mL, and the Ki were 2.33 mg/mL, 5.96 mg/mL and 3.64 mg/mL. The Ginkgo biloba leaf alcohol extract was a mild inhibitor on xanthine oxidase and belong to the competitive inhibition, and the Ki was 3.64 mg/mL.The vitro inhibition tests on xanthine oxidase of cordycepin, puerarin, maslinic acid, panax ntoginseng saponins and quercetin had been finished. The resulted show that, maslinic acid and panax ntoginseng saponins had no effects on XO. Puerarin and cordycepin were belong to mild xanthine oxidase inhibitor. Quercetin had good inhibition on the xanthine oxidase, the inhibition rate was as high as 90%, the IC50 11.09 μg/mL, and the Ki was 8.68 μg/mL. Quercetin belong to the mixed inhibition(a mixture of competition and non-competition).The secondary structure of quercetin on xanthine oxidase was analyzed. The results showed that, with the increase of quercetin, the content of α-helix and β-turn increased, and the content of β-sheets and random coil decreased. It indicated that the combination of quercetin and XO made XO’s secondary structure closer, and inhibits the formation of enzyme activity center. |
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