Xanthine oxidase inhibitory activities of some Vietnamese medicinal plants

In the search for novel xanthine oxidase (XO) inhibitors to treat gout and other diseases associated with the XO activity, 165 chloroform, ethanolic and aqueous extracts from 55 parts of 21 plants, belonging to 7 families, selected from Vietnamese medicinal plants, were screened for their XO inhibitory [1] potential. 21 extracts of 7 plants showed the XO inhibitory activity higher than 50% at concentration of 1mg/ml. Of these, 8 extracts belonging to 3 plants still inhibited XO activity higher than 25% at concentration of 0.125mg/ml.

The 2 highest active plants were further investigat, guided by XO assay. From trunk of Flacourtia rukam Zoll. et Mor. (Flacourtiaceae), vanillic acid and poliothrysosid were isolated. Their IC₅₀ (μM) of XO inhibitory activity compared to that of allopurinol were 61, 18 and 22, respectively. From stem woods of Gnetum latifolium Blume (Gnetaceae), 7 pure compounds, i.e. gnetol, trans-resveratrol, gnetifolin A, chrysoeriol, isorhapontigenin, 2,4-dihydroxy-3-methoxystilbene and 4ʹ,5,7-trihydroxy-3ʹ,8-dimethoxyflavone were isolated. IC₅₀ (μM) of gnetol and trans-resveratrol, compared that of allopurinol on XO inhibitory activity were 242, 164 and 23, respectively.

The chloroform extract of Gnetum latifolium was also studied on hyperuricemia pretreated with oxonate. At dose of 150mg/kg, after 7 and 14 day of experiment, the extract revealed the effect of reducing serum uric acid level comparable with that of allopurinol (10mg/kg). The study showed the potential of Vietnamese medicinal plants for XO inhibitors that can be developed, upon further investigation, for treatment of gout and other XO-related disorders.

• References

• 1 Lin. , Huang AM, Tu HY, Weng JR, Hour TC, Wei BL, Yang SC, Wang JP, Pu YS, Lin CN. Phloroglucinols Inhibit and, and -by in and. J Agric Food Chem 2009; 57: 8782-8787