Abstract:
Emergence of new and re‐emergence of old infections continue to elude prospects of
reducing morbidity and mortality caused by microbial infections. Trends of resistance to currently in
use antimicrobials and antimalarials threaten to increase mortality caused by these infections. This
study explores the potential of marine invertebrates as a source for new antimicrobials and
antimalarials. The lactate dehydrogenase method was used to assay marine sponges for activity
against Plasmodium falciparum, while the disc diffusion method was used to assay the extracts for
antibacterial and antifungal activity. Extracts of some marine sponges from the Zanzibar Island
exhibited both antiplasmodial and antimicrobial activities. Among the 55 marine sponge extracts that
were tested 23 (41.8%) inhibited Plasmodium falciparum W2 strain by more than 50% at both 250 and 50
μg/ml concentrations. Moderate polar extracts were more active against Plasmodium falciparum W2
strain than polar and non‐polar extracts. None of the 12 extracts that were tested on Plasmodium
falciparum strain D6 exhibited inhibitory activity reaching 50%. Among 18 marine sponge extracts that
were tested for antimicrobial activity 12 (66.7%) showed activity against one or more of the bacteria
and fungi used ranging from weak to strong on an arbitrary criterion. The ethyl acetate extracts of
Agelas mauritania and Oceanopia sp. exhibited high activity against the fungi Candida albicans and
Cryptococcus neoformans. The best antibacterial profile was exhibited by ethyl acetate extracts of
Aplysinopsis sp., Halichondrida sp. 1 and Oceanopia sp. In conclusion, these results support the need for
intensified efforts to search for active antimalarial and antimicrobial compounds from the Zanzibar
marine sponges.
