Bioactive 30-noroleanane triterpenes from the pericarps of Akebia trifoliata

Two new 30-noroleanane triterpenes, 2α,3β,20α-trihydroxy-30-norolean-12-en-28-oic acid (1), 2α,3β-dihydroxy-23-oxo-30-norolean-12,20(29)-dien-28-oic acid (2), were isolated from the pericarps of Akebia trifoliata, together with four known ones, 3β-akebonoic acid (3), 2α,3β-dihydroxy-30-noroleana-12,20(29)-dien-28-oic acid (4), 3α-akebonoic acid (5) and quinatic acid (6). Their structures were established on the basis of detailed spectroscopic analysis, and they were all isolated from the pericarps of A. trifoliata for the first time. Compounds 3-6 showed in vitro bacteriostatic activity against four assayed Gram-positive bacterial strains. In particular 3 showed antibacterial activity toward MRSA with a MIC value 25 μg/mL, which was more potent than kanamycin (MIC 125 μg/mL). No compounds showed antibacterial activity toward the three Gram-negative bacteria tested. Compounds 4 and 5 showed interesting in vitro growth inhibitory activity against human tumor A549 and HeLa cell lines, with IC50 values ranging from 8.8 and 5.6 μM, respectively. Compounds 1, 2, 5 and 6 were further revealed to show significant in vitro α-glucosidase inhibitory activity with IC50 values from 0.035 to 0.367 mM, which were more potent than the reference compound acarbose (IC50 0.409 mM).