New steroidal saponin from Antigonon leptopus Hook. and Arn.

Background: Antigonon leptopus Hook. and Arn., Polygonaceae (cadena de amor), is a herbal remedy for pain and gout-like symptoms in the Philippines. The methanol extract of A. leptopus have shown strong inhibitory action against xanthine oxidase. Objective: To isolate and identify the compound responsible for the xanthine oxidase inhibitory action. Materials and Methods: A bioassay-guided isolation scheme using an in vitro assay for the inhibition of xanthine oxidase was employed. The structure was established using spectroscopic analysis and chemical methods. Results: The isolated compound was determined to be a noncompetitive inhibitor of xanthine with an IC50 of 1.79 μg/mL. Conclusion: The isolated compound may represent a new class of xanthine oxidase inhibitors.