Extracts of the cyanobacteria Microcystis flos-aquae contain potent anti- Trypanosoma compounds

To find new compounds for future development of anti- Trypanosoma drugs, we investigated cyanobacteria for secondary metabolites that kill trypanosomes, the parasites causing trypanosomiasis. Crude methanolic extracts of four cyanobacteria ( Microcystis aeruginosa EAWAG198, Microcystis flos-aquae UTEX 2677, Microcystis wesenbergii NIES-104, and Oscillatoria sp.) were prepared and tested on Trypanosoma brucei brucei for trypanosome-killing activity. The most active crude extract was fractionated by liquid column chromatography. Trypanocidal fractions were identified by incubating each fraction with trypanosomes and monitoring parasite death under 400× microscopic magnification. A crude extract of M. flos-aquae was also used to treat rats infected with T. b. brucei . The crude extract of M. flos-aquae exhibited the highest in vitro trypanocidal activity, with percentage inhibitions of 98.44 and 42.18% at 2.5 and 0.3125 mg mL -1 , respectively, and an IC 50 value of 0.414 mg mL -1 . The most active fraction E exhibited the highest in vitro activity against the parasite, with a percentage inhibition of 74.21 % at 0.625 mg mL -1 and an IC 50 value of 0.299 mg mL -1 . The active sub-fraction of E ( Es ) exhibited 76% inhibition at the same concentration. Interestingly, the crude extract of M. flos-aquae also suppressed parasite proliferation in treated animals and improved the weight and PCV of rats treated with dosages above 60 mg kg -1 body weight. The GC/MS profile of fraction Es revealed the presence of Cedran-diol, Ethyl-5-(furan-2-yl)-1,2-oxazole-3-carboxylate,5-amino-1-tetrazolylacetic acid, 2-amino-4-(2-methylpropanyl)-pyrimidine-5-carboxylic acid, and others. In conclusion, our findings demonstrate that cyanobacteria could be considered promising sources of lead compounds for the development of new trypanocidal drugs.