In vitro study of the antibiotic activity of diterpenes.

The antibiotic activity of 16 diterpenes and of 2 phenanthrene derivatives of diterpene origin, isolated from Brazilian plants was investigated against bacteria, yeasts, dermatophytes and aflatoxin-producing fungi. Eight of the compounds were completely inactive. None showed inhibitory activity against the Gram-negative bacteria assayed or against the Aspergillus species. The phenanthrene derivatives, chemically very similar to phytoalexins isolated from orchids, were especially active.