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 (IC
50 = 0.017 ± 0.001 mg/mL) and formation of superoxide
(IC
50 = 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.
