(±)-Gnetuparin A: a pair of stilbene enantiomers from Gnetum parvifolium and their xanthine oxidase inhibitory activity.

(±)-Gnetuparin A (1a/1b), a pair of stilbene enantiomers characterized by a 6/5/5 tricyclic ring system, were isolated from the stems of . The racemic mixture of 1a/1b was separated on a chiral high-performance liquid chromatography (HPLC) column. The absolute configurations of the enantiomers were established by comprehensive spectral analysis in combination with a quantum chemical calculation. Structurally, compounds 1a/1b feature a novel skeleton based on a stilbenoid coupled with a methylcyclopentanone, forming a rare cyclopenta[]furan-6-one motif. A hypothetical biosynthetic pathway for 1a/1b was proposed. Biological investigations showed that 1a and 1b exhibited good xanthine oxidase inhibitory activities with IC values of 74.9 and 56.1 µM, respectively. Moreover, an enzyme kinetic analysis revealed that compound 1b acted as a noncompetitive inhibitor of xanthine oxidase with a value of 54.72 μM. This study not only revealed the structure and inhibitory activity of 1a/1b against xanthine oxidase but also provides a theoretical basis for the development of new uric-acid-lowering drugs from .