In vitro activity of selected Ghanaian medicinal plants against parasites: Giardia lamblia, Entamoeba histolytica and Naegleria fowleri

Entamoeba histolytica and Giardia lamblia are parasitic protozoa that cause gastrointestinal disorders such as diarrhea and dysentery. Naegleria fowleri is a free living amoeba that causes primary amoebic meningoencephalitis. However, there are limited treatments for these parasitic diseases. Extracts, fractions from extracts and some isolated compounds from selected Ghanaian medicinal plants were screened against Naegleria fowleri, Giardia lamblia and Entamoeba histolytica in the search for newer and safer agents for the treatment of infections caused by these parasites. Of all the extracts and compounds tested for the activity against E. histolytica, only xylopic acid and geraniin were active with IC50 values of 4.80 μg/mL (13.30 μM) and 34.71 μg/mL (36.44 μM), respectively. Metronidazole, the positive control had an IC50 of 1.287 μM. All other extracts and fractions exhibited IC50 values >100 μg/mL. For G. lamblia, extracts of Albizia glaberrima, Margaritaria nobilis, Maerua angolensis and Ulva fasciata, the ethyl acetate fraction of Erythrophleum ivorense bark extract, and the isolated compound, xylopic acid exhibited IC50 values of 15.91, 44.25, 20.00, 35.86, 13.76 and 11.45 μg/mL, respectively. The IC50 of the positive control agent metronidazole, was 10.47 μM. The extract of A. glaberrima and xylopic acid exhibited IC50 values of 38.70 and 16.06 μg/mL, respectively, against N. fowleri. The IC50 of the reference drug, amphotericin B, was 0.2 μM. Thus, Ghanaian medicinal plant extracts, their fractions and isolated compounds possess anti-parasitic activity.