Antifilarial activity of marine sponge Haliclona oculata against experimental Brugia malayi infection

The present study incorporates the findings on in vitro and in vivo antifilarial activity in the marine sponge, Haliclona oculata using an experimental rodent infection of human lymphatic filarial parasite, Brugia malayi. The in vitro antifilarial action was determined on both adult female worms as well as microfilariae using two parameters viz. adverse effect on motility and inhibition in MTT reduction by the treated adult parasite over control worm. The antifilarial activity could be located in the methanol extract and one of its four fractions (chloroform). Bioactivity guided fractionation of chloroform fraction led to localization of in vitro activity in one of its eight chromatographic fractions. Methanol extract, chloroform fraction and one of the chromatographic fractions revealed IC₅₀ values of 5.00, 1.80, and 1.62μg/ml, respectively when adult B. malayi were exposed to these test samples for 72h at 37°C. Under similar exposure conditions, the IC₅₀ values for microfilariae were 1.88, 1.72 and 1.19μg/ml, respectively. The active test samples were found to be safe revealing >10 selectivity indices (SI) on the basis of cytotoxicity to Vero cells (monkey kidney cells) and therefore selected for in vivo evaluation against primary (adult B. malayi intraperitoneal transplanted jird) and secondary (subcutaneous infective larvae induced mastomys) screens. In primary jird model, the three test samples at 100mg/kg for five consecutive days by subcutaneous route demonstrated significant macrofilaricidal efficacy to the tune of 51.3%, 64% and 70.7% by methanol extract, chloroform and chromatographic fraction, respectively. The three samples demonstrated 45–50% macrofilaricidal activity with moderate embryostatic effect in secondary model at 5×500, 5×250 and 5×125mg/kg by oral route. Chromatographic fraction possessing highest antifilarial action was primarily found to be a mixture of four alkaloids Mimosamycin, Xestospongin-C, Xestospongin-D and Araguspongin-C in addition to few minor compounds.