Antimicrobial ent-abietane diterpenoids from the leaves of Croton cascarilloide

Three new ent-abietane diterpenoids, 6β-hydroxy-ent-abieta-7,13-dien-3-one (1), 2β,13α,15-trihydroxy-ent-abieta-8(14)-en-3-one (2), and 2β,9α,13β,15-tetrahydroxy-ent-abieta-7-en-3-one (3), were isolated from 90% ethanol extract of the leaves of Croton cascarilloide. Their structures were determined by spectral methods such as 1D and 2D (¹H-¹H COSY, HMQC, NOESY, and HMBC) NMR spectroscopy, in addition to electronic circular dichroism (ECD) spectra. The isolated diterpenoids were tested in vitro for antimicrobial activity against 6 pathogenic microorganisms. As a result, compounds 1-3 exhibited antimicrobial activity against the tested Gram positive bacteria with minimum inhibitory concentration values less than 50 μg/ml.