Antiplasmodial activity of extracts of 25 cyanobacterial species from coastal regions of Tamil Nadu

Abstract

Context: Marine cyanobacteria offer considerable potential to isolate new antimalarials to meet a pressing need of our times.Objective: To explore the antiplasmodial properties of marine cyanobacteria.Materials and methods: Cyanobacterial samples collected from the coastal regions of Tamil Nadu were identified using light microscopy, and the strains were cultivated in ASN-III medium. Organic extracts (0–100 µg mL−1) of 25 in vitro mass-cultivated cyanobacteria, prepared using methanol: chloroform mixture (1:1 v/v) were evaluated for their antiplasmodial activity against chloroquine-sensitive and -resistant strains of Plasmodium falciparum by fluorescence-based SYBR Green I assay where chloroquine was used as a control. To detect the toxic effects of cyanobacterial extracts against red blood cells, the invasion, maturation, and growth rate of malarial parasites in cyanobacterial extracts pre-treated versus untreated erythrocytes were quantified microscopically. Mammalian cell line (HeLa) was used to determine cyanobacterial extract toxicity using the MTT assay.Results: The extracts of Lyngbya aestuarii Liebm. ex Gomont CNP 1005 (C12) Oscillatoria boryana BDU 91451 (C22) and Oscillatoria boryana Bory ex Gomont BDU 141071 (C18) showed promising antiplasmodial activity (IC50 = 18, 18, and 51 μg mL−1 respectively) against Pf3D7. Pretreatment of red blood cells with IC100 of C12, C18, and C22 (40, 100, and 40 µgmL−1, respectively) did not significantly influence the invasion, maturation, and growth rate of malarial parasites in comparison with untreated RBC controls suggesting a lack of toxicity to host cells. MTT assay based IC50 (>200 μg mL−1) of these extracts against HeLa cell line also indicates their high selectivity against the malaria parasite.Discussion and conclusion: These exploratory studies suggest the possibilities of development of new antimalarial compounds from marine cyanobacteria.