Antiparasitic activity of flavonoids and isoflavones against Cryptosporidium parvum and Encephalitozoon intestinalis

Abstract

Flavonoids, polyphenolic compounds found in plants, have demonstrated activity against several parasites and can augment the efficacy of other drugs by either increasing the uptake or decreasing the efflux of these drugs. We evaluated 11 of these compounds alone or in combination in order to test the hypothesis that flavonoids are effective against Cryptosporidium parvum and Encephalitozoon intestinalis. Using in vitro cell culture assays, HCT-8 cells or E6 cells were infected with C. parvum and E. intestinalis, respectively, and treated with compounds at doses ranging from 1 to 200 μM. We found that six compounds were active against C. parvum. Naringenin and genistein had the greatest activities with EC50 of 15 and 25 μM, respectively. Two compounds, quercetin and apigenin, had activity against E. intestinalis at EC50 of 15 and 50 μM, respectively. The EC50 of trifluralin, a dinitroaniline compound, was decreased significantly when combined with genistein in an in vitro assay, suggesting that compounds may be used alone on in combination with other moderately active drugs to increase efficacy. In addition, induction of apoptosis by these compounds was studied but not observed to be a significant mechanism of action. © 2006 Federation of European Microbiological Societies Published by Blackwell Publishing Ltd.