Antiprotozoal and cytotoxic potential of British and Irish red algae

Marine algae are a prolific source of diverse natural products, but their biomedical potential has barely been explored. As part of our continuing research on seaweeds [1], we have screened crude extracts of 23 marine red algae (Rhodophyta) collected from Britain and Ireland. Algal material was extracted with CHCl₃: MeOH mixtures (3:1 and 1:1) at room temperature and evaporated to dryness in vacuo before use in bioassays. The clinically important blood-stage life forms of Trypanosoma brucei rhodesiense, T. cruzi and Leishmania donovani were used as test organisms in the in vitro assays. The selective toxicity of the extracts was determined towards mammalian skeletal myoblast (L6) cells. All algal extracts showed activity against T. brucei rhodesiense, with Corallina officinalis (Corallinaceae) and Ceramium virgatum (Ceramiaceae) being the most potent (IC₅₀ values 4.8 and 5.4µg/ml, respectively), whilst none of the algal extracts inhibited the growth of T. cruzi. With the exception of a Porphyra leucosticta (Bangiaceae) extract, all seaweed extracts also displayed leishmanicidal activity with IC₅₀ values ranging from 16.5 to 85.6µg/ml. Corallina officinalis was the only seaweed that showed some marginal cytotoxicity (IC₅₀ value 88.6µg/ml), whereas all remaining extracts were non-toxic towards L6 cells at 90µg/ml concentration. To our knowledge, this is the first study reporting antiprotozoal activity of British and Irish red algae.

References: 1. Orhan, I. et al. (2006) Phytomedicine 13:388–393.