Kinetics of Inhibition of Xanthine Oxidase by Lycium arabicum and its Protective Effect against Oxonate- Induced Hyperuricemia and Renal Dysfunction in Mice

I Krache,A Baghiani,L Arrar,N Charef,H Trabsa,S Khennouf,N Boussoualim

doi:10.4314/tjpr.v14i2.9

Abstract

Purpose: To evaluate the in-vitro inhibition of xanthine oxidase (purified from bovine milk) by extracts of Lycium arabicum, as well as it is in vivo hypouricemic and renal protective effects.Methods: Four extracts of Lycium arabicum, methanol (CrE), chloroform (ChE), ethyl acetate (EaE) and aqueous (AqE) extracts, were screened for their total phenolics and potential inhibitory effects on purified bovine milk xanthine oxidase (XO) activity by measuring the formation of uric acid or superoxide radical. The mode of inhibition was investigated and compared with the standard drugs, allopurinol, quercitin and catechin. To evaluate their hypouricemic effect, the extracts were administered to potassium oxonate-induced hyperuricemic mice at a dose of 50 mg/kg body weight.Results: The results showed that EaE had the highest content of phenolic compounds and was the most potent inhibitor of uric acid formation (IC50 = 0.017 ± 0.001 mg/mL) and formation of superoxide (IC50 = 0.035 ± 0.001 mg/ml). Lineweaver-Burk analysis showed that CrE and EaE inhibited XO competitively, whereas the inhibitory activities exerted by ChE and AqE were of a mixed type. Intraperetoneal injection of L. arabicum extracts (50 mg/kg) elicited hypouricemic actions in hyperuricemic mice. Hyperuricemic mice presented a serum uric acid concentration of 4.71 ± 0.29 mg/L but this was reduced to 1.78 ± 0.11 mg/L by EaE, which was the most potent hyporuricemic extract.Conclusion: L. arabicum fractions have a strong inhibitory effect on xanthine oxidase and and also have a significantly lowering effect on serum and liver creatinine and urea levels in hyperuricemic mice.Keywords: Lycium arabicum, Uric acid, Creatinine, Superoxide, Phenolic compounds, Flavonoids, Hyperuricemia

Highlights

Xanthine oxidoreductase (XOR) is part of a group of enzymes known as molybdenum ironsulfur flavin hydroxylases
Each subunit contains a single peptide chain, which binds one molybdopterin cofactor (Mo-pt), two non identical 2Fe–2S centers, and one FAD cofactor. It exists in two interconvertible forms known as xanthine oxidase (XO) and xanthine dehydrogenase (XDH) XOR is involved in the oxidation of hypoxanthine to xanthine and xanthine to urate [1]
The obtained organic layer of each partition was evaporated under reduced pressure on a rotavapor below 45 °C to dryness and to afford hexane, chloroform, ethyl acetate and aqueous fractions coded as HxE, competitive type and the nonglucosidic flavonoids (ChE), EaE and AqE, respectively

Summary

INTRODUCTION

Xanthine oxidoreductase (XOR) is part of a group of enzymes known as molybdenum ironsulfur flavin hydroxylases. The obtained organic layer of each partition was evaporated under reduced pressure on a rotavapor below 45 °C to dryness and to afford hexane, chloroform, ethyl acetate and aqueous fractions coded as HxE, ChE, EaE and AqE, respectively All of these fractions were stored at -20 °C prior to use. The effect of L. arabicum extracts on XO was examined spectrophotometrically at 295 nm by following the production of uric acid using an absorption coefficient of 9600 M-1 cm-1 [9]. Different concentrations of tested compounds and extracts were added to and their effect on the generation of uric acid was used to calculate regression lines. The results are expressed as extract concentration that inhibited 50 % of enzyme activity (IC50).

RESULTS

DISCUSSION

CONCLUSION