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

Abstract Two new ent -kaurane diterpenoids, 16 α ,17,19-trihydroxy-18-nor- ent -kauran-4 β -ol ( 1 ) and 17-chloro-16 β -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 μg/mL) comparable to reference compound Kanamycin (MIC 3.125 μg/mL). Compounds 4 – 6 further displayed significant antibacterial activity against Gram-(−) bacterium Shigella dysenteriae with MIC value 3.125–12.5 μg/mL.