Antiprotozoal,antimycobacterial and cytotoxic potential of twenty‐three British and Irish red algae

As part of our continuing research on seaweeds, we have screened the crude extracts of 23 red marine algae collected from England and Ireland. The clinically important blood‐stage life forms of Trypanosoma brucei rhodesiense, T. cruzi, Leishmania donovani and Mycobacterium tuberculosis were used as test organisms in the in vitro assays. The selectivity of the extracts was determined by using mammalian skeletal myoblast (L6) cells. All algal extracts showed activity against T. brucei rhodesiense, with Corallina officinalis and Ceramium virgatum being the most potent (IC₅₀ values 4.8 and 5.4 μg/ml), whilst none of the algal extracts inhibited the growth of T. cruzi. Except for Porphyra leucosticta, extracts from all seaweeds also showed leishmanicidal activity with IC₅₀ values ranging from 16.5 to 85.6 μg/ml. Only the crude extract of Calliblepharis jubata showed some weak activity against Mycobacterium tuberculosis (MIC value 256 μg/ml), while the others were inactive at this concentration. Corallina officinalis was the only seaweed that displayed some marginal cytotoxicity (IC₅₀ value 88.6 μg/ml), and all remaining extracts were non‐toxic towards L6 cells at 90 μg/ml concentration. To our knowledge, this is the first study reporting antiprotozoal and antimycobacterial activity of British and Irish red algae. Copyright © 2010 John Wiley & Sons, Ltd.