Molecular Characterization and Bioactivity of Coumarin Derivatives from the Fruits of <i>Cucumis bisexualis</i>

Abstract

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-2 H-chromen)-6-prenyl-2 H-chro-men-2-one (1), 7-hydroxy-3-(5'-prenyl-3″,3″-dimethyl-2 H-chromen)-6-prenyl-2 H-chromen-2-one (2), 3-(6'-hydroxy-5'-prenyl-3″,3″-dimethyl-2 H-chromen)-6-prenyl-2 H-chromen-2-one (3), 3-(5'-ethyl-3″,3″-dimethyl-2 H-chromen)-6-prenyl-2 H-chromen-2-one (4), 3-(4',6'-dihydroxy-5'-dimeth-ylallyl-3″,3″-dimethyl-2 H-chromen)-6-prenyl-2 H-chromen-2-one (5), 3-[4',6'-dihydroxy-5'-(2-pro-penyl)-3″,3″-dimethyl-2 H-chromen]-14,15-dimethyl-pyrano-chromen-2-one (6), 3-(6'-dihydroxy-5'-isopropanol-3″,3″-dimethyl-2 H-chromen)-14,15-dimethyl-pyrano-chromen-2-one (7), 3-(5'-iso-pentenol-3″,3″-dimethyl-2 H-chromen)-14,15-dimethyl-pyrano-chromen-2-one (8), 3-(4',6'-dihydr-oxy-5'-prenyl-3″,3″-dimethyl-2 H-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 μM, and compounds 2, 4, 12, 15, 17, 18, and 19 (10 μM) 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.