Rickards, RodneyRothschild, JenniferWillis, Anthonyde Chazel, NolaKirk, JKirk, KiaranSaliba, KevinSmith, Geoffrey D2015-12-130040-4020http://hdl.handle.net/1885/92065Cell extracts from photoautrophic cultures of two cyanobacterial Calothrix isolates inhibited the growth in vitro of a chloroquine-resistant strain of the malaria parasite, Plasmodium falciparum, and of human HeLa cancer cells, in a dose-dependent manner. Bioassay-directed fractionation of the extracts led to the isolation and structural characterization of calothrixins A (1) and B (2), pentacyclic metabolites with an indolo[3,2- j]phenanthridine ring system unique amongst natural products, which exert their growth-inhibitory effects at nanomolar concentrations.Keywords: calothrixin a; calothrixin b; indole derivative; phenanthridine derivative; unclassified drug; article; bacterium culture; bacterium isolate; cancer cell; cyanobacterium; drug isolation; drug structure; hela cell; human; human cell; malaria; nonhuman; pla Anticancer; Antiplasmodial; Cyanobacteria; Polycyclic heterocyclic compounds199910.1016/S0040-4020(99)00833-92015-12-12