Phytochemical investigation of the stem bark of the recently described species Monodoracarolinae (Annonaceae) afforded prenylindole derivatives (E)-4-(1H-indol-6-yl)-but-3-en-2-one (1), 5-formylindole (2), fatty acid (Z)-hexade-7-enoic acid (3) and the lignanamide cannabisin B (4). The structures of the isolated compounds were established using NMR and MS analyses. The antimycobacterial activities of the extracts and isolated compounds were evaluated against Mycobacterium madagascariense (MM) and M. indicus pranii (MIP) using the two-fold microtitre dilution method. While the extracts exhibited minimum inhibitory concentration (MIC) ranging from 500 €“ 1000 μg/mL, the isolated compounds were 125 €“ 250 μg/mL, indicating very low activity. Cytotoxic effects were evaluated using brine shrimp larvae whereby the ethanolic extract of the root bark exhibited the lowest LC50 (< 3μg/mL). Isolation of prenylindole derivatives is of chemotaxonomic significance that affirms taxonomic placement of this plant species into the genus Monodora. This is the first time cannabisin B is reported from the genus Monodora.
