| Xanthine Oxidase (EC 1.1.3.2.2, XOD), a key enzyme in the process of purine metabolism, catalyses the oxidation of hypoxanthine to xanthine and subsequently to uric acid, hydrogen peroxide and superoxide. The high concentration of uric acid in body would cause hyperuricemia and finally lead to gout, and persistent hyperuricemia would reduce hypertension, hyperlipaemia, cardiovascular disease and chronic nephrosis. In recent years, the XOD inhibitor as a effective anti-hyperuricemia drug has garnered widespread concern of research scholars at home and abroad. However, most of the xanthine oxidase inhibitors used in clinical application generally suffer from many adverse side effects. Therefore, searching for new XOD inhibitors from natural bioactivator with efficient inhibition and few side effects would provide a new direction for the study of anti-hyperuricemia drug.In this reasearch, we studied the inhibitory effect of polysaccharide and polyphenol from Sargassum thunbergii Kuntze and Laminaria japonica Aresch on XOD, and we determined their IC50 on XOD in vitro. Their inhibition mechanism, inhibition types and inhibition constant were studied by enzyme kinetic analysis. The joint inhibitor effects of the polysaccharide and polyphenol from two seaweeds with allopurinol were examined using a toxic equivalency method. This research also determined the free radical scavenging activity of the polysaccharide and polyphenol from two seaweeds in vitro. we also studied the influence of L. japonica polysaccharide on mice of hyperuricimia by establishing a hyperuricemic animal model pretreated with potassium oxonate. The concerte results were as follows:The results demonstrated that both of S. thunbergii polyphenol and polysaccharide had a remarkblely inhibited activity on XOD. And the IC50 of S. thunbergii polyphenol and polysaccharide were 0.58mg/mL and 1.21mg/mL, respectively. The inhibition kenitic analyzed revealed that the inhibition type of them were competitive inhibiton, and the Ki were 0.07mg/mL and 0.46mg/mL. The IC50 of L. japonica polyphenol and polysaccharide were 0.88mg/mL and 1.63mg/mL. The inhibition type of L japonica polysaccharide was competitive inhibiton, and its Ki was 0.30mg/mL. While L. japonica polyphenol was a noncompetitive inhibitor, and its Ki was 0.21mg/mL. In this study, we also determined the type of associated inhibion of polyphenol and polysaccharide from two seaweeds, and the result showed that the mixture of allopurinol and S. thunbergii polysaccharide has synergistic inhibitory effect against XOD, and the similar results existed with L. japonica polysaccharide and polyphenol. While the joint inhibitor effect of S. thunbergii with allopurinol was weak synergistic inhibitory effect.The polysaccharide and polyphenol from S. thunbergii and L. japonica revealed high scavenging activity on both OH- and O2- in vitro. Both of polysaccharide and polyphenol from S. thunbergii had high clearance rate on OH- which was over than 50%, and the clearance rate would increase with the increase of scavenger concentration. However, the scavenging activity on O2- was much weaker, and the highest clearance rate was 61.86%, whose dose-response relationship was not significant. L. japonica polyphenol and polysaccharide showed a stronger scavenging activity on OH-, and the highest clearance rate could reach 92.13%, and the dose dependent effect is remarkable. While the scavenging activity on 02-was not good as OH-, the dose dependent effect was neither remarkable.After 7 days of administration of L. japonica polysaccharide with different doses, L. japonica polysaccharide high-dose group and middle-dose group made the serum uric acid level of hyperuricemic mice significantly lower than the model group (P<0.05), and the hepatic XOD activities were reduced significantly (P<0.05) either, which proved that L. japonica polysaccharide can significantly reduce the serum uric acid level of hyperuricemic mice and produce significant decreases in XOD activities in mouse liver. Meanwhile, the serum uric acid values of high-dose group and middle-dose group had no significant differences (P>0.05) with normal group, which proves that the serum uric acid of hyperuricemic mice has been restored to normal levels. In addition, we also found that the mice of L. japonica polysaccharide groups had good growth conditions and mental state, and there was no death was discovered. It is concluded that L. japonica polysaccharide can be expected to be a drug which is safe and reliable for the treatment of hyperuricaemia.The polysaccharide and polyphenol from S. thunbergii and L. japonica have high inhibited capability on XOD and strong scavenging activity on both OH- and O2- in vitro. The L. japonica polysaccharide possesses potent anti-hyperuricemic effects on models of hyperuricemia in mice pretreated with potassium oxonate. Futhermore, L. japonica is a kind of edible algae, which is safe, abundant on nutrition and has a variety of biological activities. As a normal seaweed along the coast, S. thunbergii is widespreading and full-year growth, which has not been fully development and utilization. Therefore, the polysaccharide and polyphenol from S. thunbergii and L. japonica serve as anti-hyperuricemia drugs and antioxidant have good development prospect, and this article provides a new research idea for further development and application of S. thunbergii and L. japonica. |
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