Bioactive Constituents from Mesona Chinensis: Chemical Evidence for Its Antihyperuricemic Activity

Mesona chinensis Benth. (Lamiaceae) has been shown antihyperuricemic effect in vivo. This study was aimed to provide chemical evidence for such bioactivity. Three new compounds (3, 4, and 8) together with 14 known were isolated from the n-BuOH soluble fraction of its aerial part. All the structures were elucidated based on the spectroscopic analysis. This effort also revised the reported structure for mesonolate B. Except for 2 and 6, the remaining 15 isolates are reported for the first time from the title plant. Preliminary quantification of four majors (1, 5, 6, 8) by liquid chromatography-mass spectroscopy (LC-MS) (EIC) indicated their content in the dried aerial part to be 788, 146, 177, and 97 ppm (w/w), respectively. Among these isolates, 3-O-(6-O-feruloyl-beta-d-glucosyl)-rosmarinic acid (3) was shown xanthine oxidase inhibition besides the reported rosmarinic acid (1), lithospermic acid A (5), isoquercitrin (11), and ursolic acid (13). In addition, compounds 2-4, 6 and 7, and 12 could be hydrolyzed to the corresponding active metabolites 1, 5, and 11 in the GI tract. Thus, this chemical investigation verified the reported hypouricemic effect of M. chinensis. Accordingly, this herbal medicine should have great potential to be developed as an antihyperuricemic nutraceutical.