Bioactivity-guided fractionation of the acetone extract of Elephantopus scaber (ES) yielded a new terpenoid, 6-[1-(10,13-dimethyl-4,5,8,9,10,11,12,13,14,15,16,17-dodecahydro-1H-cyclopenta[α]phenanthren-17-yl)ethyl]-3-methyl-3,6-dihydro-2 H-2-pyranone. The structure of the above mentioned compound was elucidated by interpretation of their spectroscopic data. Biological testing of the compound demonstrated significant antibacterial activity against a few multi drug-resistant ESBL-producing clinical isolates. The crude plant extracts demonstrated zones of inhibition in the range of 5-16 mm against the chosen test bacteria. On the basis of promising activity, acetone extracts were selected to determine their efficacy in terms of Minimal Inhibitory Concentration (MIC), which ranged from 1.6-25 mg mL-1. The acetone extract was subjected to activity-guided fractionation. The most effective fraction had a MIC of 62.5-250 μg mL-1. Phytochemical analysis showed the presence of terpenoids, proteins and traces of steroids. TLC bioautography of the fraction showed the active compound to be terpenoids.
R. Jasmine, P. Daisy and B.N. Selvakumar, 2007. A Novel Terpenoid from Elephantopus scaber with Antibacterial Activity Against Beta-lactamase-Producing Clinical Isolates. Research Journal of Microbiology, 2: 770-775.