Molecular Characterization and Bioactivity of Coumarin Derivatives from the Fruits of Cucumis bisexualis

Cucumis bisexualis (Cucurbitaceae) is known as "mapao egg" or "muskmelon egg", which has been widely used as a wild melon in Chinese folk. Nine new coumarin derivatives (1-9), named 7-hydroxy-3-(4',6'-dihydroxy-5'-isopropyl-3 '',3 '' dimethyl-2H-chromen)-6-prenyl-2H-chromen-2-one (1), 7-hydroxy-3- (5 '-prenyl-3 '',3 ''-dim ethyl-2H-chromen )-6-prenyl-2H-chromen-2-one (2), 3-(6'-hydroxy-S'-prenyl-3 '',3 ''-dimethyl-2H-chromen)-6-prenyl-2H-chromen-2-one (3), 3-(5'-ethyl-3 '',3 '' dimethyl-2H-chromen)-6-prenyl-2H-chromen-2-one (4), 3-(4',6'-dihydroxy-S'-dimeth-ylallyl-3 '',3 ''-dimethyl-2H-chromen)-6-prenyl-2H-chromen-2-one (5), 344',6'-dihydroxy-5'-(2-pro-penyl)-3 '',3 ''-dimethyl-2H-chromenl-14,15-dimethyl-pyrano-chromen-2-one (6), 3-(6'-dihydroxy-5'-isopropanol-3 '',3 ''-dimethyl-2H-chromen)-14,15-dimethyl-pyrano-chromen-2-one (7), 3(5'-iso-pentenol-3 '',3 ''-dimethyl-2H-chromen)-14,15-dimethyl-pyrano-chromen-2-one (8), 3-(4',6'-dihydr-oxy-5'-prenyl-3 '',3 '' dimethyl-2H-chromen)-14,15-dimethyl-pyrano-chromen-2-one (9), together with 12 known compounds (10-21), were isolated and identified by spectroscopic analysis and references from the active site (EtOAc soluble fraction) of the fruits of C. bisexualis for the first time. Compounds (1-21) were evaluated for antiacetylcholinesterase (AChE) and hepatoprotective activities for the first time. Compounds 1, 3, 5, 6, 7, and 9 showed anti-AChE activities with IC50 values ranging from 11.23 to 89.69 mu M, and compounds 2, 4, 12, 15, 17, 18, and 19 (10 mu M) exhibited moderate hepatoprotective activities. These findings shed much light on a better understanding of the anti-AChE and hepatoprotective effects of these coumarin derivatives and provided new insights into developing better anti-AChE and hepatoprotective drugs in the future.