Xanthine oxidase inhibitors from Archidendron clypearia (Jack.) I.C. Nielsen: Results from systematic screening of Vietnamese medicinal plants

Abstract

Objective: To screen Vietnamese medicinal plants for xanthine oxidase (XO) inhibitory activity and to isolate XO inhibitor(s) from the most active plant.

Methods: The plants materials were extracted by methanol. The active plant materials were fractionated using different organic solvents, including n-hexane, ethyl acetate, and n-butanol. Bioassay-guided fractionation and column chromatography were used to isolate compounds. The compounds structures were elucidated by analysis of spectroscopic data, including IR, MS, and NMR.

Results: Three hundreds and eleven methanol extracts (CME) belonging to 301 Vietnamese herbs were screened for XO inhibitory activity. Among these plants, 57 extracts displayed XO inhibitory activity at 100 μg/mL with inhibition rates of over 50%. The extracts of Archidendron clypearia (A. clypearia), Smilax poilanei, Linociera ramiflora and Passiflora foetida exhibited the greatest potency with IC₅₀ values below 30 μg/mL. Chemical study performed on the extract of A. clypearia resulted in the isolation of six compounds, including 1-octacosanol, docosenoic acid, daucosterol, methyl gallate, quercitrin and (-)-7-O-galloyltricetiflavan. The compound (-)-7-O-galloyltricetiflavan showed the most potent XO inhibitory activity with an IC₅₀ value of 25.5 μmol/L.

Conclusions: From this investigation, four Vietnamese medicinal plants were identified to have XO inhibitory effects with IC₅₀ values of the methanol extracts below 30 μg/mL. Compound (-)-7-O- galloyltricetiflavan was identified as an XO inhibitor from A. clypearia with IC₅₀ value of 25.5 μmol/L.

Keywords: Inhibitor; Medicinal plants; Vietnam; Xanthine oxidase.