Paenidigyamycin A, Potent Antiparasitic Imidazole Alkaloid from the Ghanaian Paenibacillus sp. DE2SH

A new alkaloid paenidigyamycin A (1) was obtained from the novel Ghanaian Paenibacillus sp. isolated from the mangrove rhizosphere soils of the Pterocarpus santalinoides tree growing in the wetlands of the Digya National Park, Ghana. Compound 1 was isolated on HPLC at t(R) = 37.0 min and its structure determined by MS, 1D, and 2D-NMR data. When tested against L. major, 1 (IC(50) 0.75 µM) was just as effective as amphotericin B (IC(50) 0.31 µM). Against L. donovani, 1 (IC(50) 7.02 µM) was twenty-two times less active than amphotericin B (IC(50) 0.32 µM), reinforcing the unique effectiveness of 1 against L. major. For T. brucei brucei, 1 (IC(50) 0.78 µM) was ten times more active than the laboratory standard Coptis japonica (IC(50) 8.20 µM). The IC(50) of 9.08 µM for 1 against P. falciparum 3d7 compared to artesunate (IC(50) 36 nM) was not strong, but this result suggests the possibility of using the paenidigyamycin scaffold for the development of potent antimalarial drugs. Against cercariae, 1 showed high anticercaricidal activity compared to artesunate. The minimal lethal concentration (MLC) and minimal effective concentration (MEC) of the compound were 25 and 6.25 µM, respectively, while artesunate was needed in higher quantities to produce such results. However, 1 (IC(50) > 100 µM) was not active against T. mobilensis.