Two new ent-kaurane diterpenoids from Wedelia trilobata (L.) Hitchc

Two new ent-kaurane diterpenoids, 16 alpha, 17,19-trihydroxy-18-nor-ent-kauran-4 beta-ol (1) and 17-chloro-16 beta-hydroxy-ent-kauran-19-oic acid (2) were isolated from the whole plant of Wedelia trilobata, together with five known ones (3-7). Their structures were elucidated on the basis of extensive spectroscopic analyses, including NMR and MS techniques. Compound 1 is an 18-nor-ent-kaurane type diterpenoid which is rare in nature, and compound 2 is the first chlorine-containing ent-kaurane diterpenoid so far isolated from plant family of Asteraceae. Known compound 4 was obtained from the genus Wedelia for the first time. Compounds 4-6 selectively showed in vitro antibacterial activity against three assayed Gram-(+) bacteria, especially 5 and 6 which showed the antibacterial activity against Staphylococcus aureus with MIC values (3.125-6.25 mu g/mL) comparable to reference compound Kanamycin (MIC 3.125 mu g/mL). Compounds 4-6 further displayed significant antibacterial activity against Gram-(-) bacterium Shigella dysenteriae with MIC value 3.125-12.5 mu g/mL. (C) 2015 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.