Cyclooxygenase-inhibitory and antioxidant constituents of the aerial parts of Antirhea acutata.

Two new compounds, (6S)-hydroxy-29-nor-3,4-seco-cycloart-4(30),24-dien-3-oic acid (1) and 8-[1-(3,4-dihydroxyphenyl)-3-methoxy-3-oxopropyl]epicatechin (3), were isolated by bioassay-guided fractionation from the aerial parts of Antirhea acutata (DC.) Urb. (Rubiaceae). Compound 1 showed moderate inhibitory activities in cyclooxygenase-1 and -2 assays (IC(50) 43.7 and 4.7 microM, respectively), while compound 3 was active in 1,1-diphenyl-2-picrylhydrazyl free-radical and cytochrome c reduction antioxidant assays (IC(50) 29.1 and 16.3 microM, respectively). Additionally, one further new compound was isolated, (3S,24S)-25-trihydroxy-9,19-cycloartane-29-oic acid (2), but this was inactive in the bioassay systems used. Compound 1 is based on the unprecedented 29-nor-3,4-seco-cycloartane skeleton.