Neolignans as xanthine oxidase inhibitors from Hyptis rhomboides.

The active fraction from the EtOH extract of Hyptis rhomboides against xanthine oxidase was identified by use of an HPLC microfractionation-centrifugal vacuum evaporation-bioassay hyphenated technique. Scale-up separation of the active subfractions using semi-preparative RP-HPLC provided 13 phenylpropanoid compounds, including O-styrenylneolignans, hyprhombins A-C, epihyprhombin B, and hyprhombin B methyl ester, and O-caffeoylnorneolignans, hyprhombins D and E. All of these compounds shared a common 1,4-benzodioxane skeleton, as established by spectroscopic analyses. Hyprhombin C and epihyprhombin B exhibited better anti-xanthine oxidase activity than allopurinol, with IC50 values of 0.6 and 2.0 μM, respectively.