Antiprotozoal Activity of a Thymus vulgaris Methanol Extract and Its Fractions

Introduction: Thymus vulgaris is used in traditional medicine to treat gastrointestinal diseases because of its antifungal, antibacterial, and antispasmodic activity. Objective: To verify whether Thymus vulgaris also has antiprotozoal activity against Trichomonas vaginalis, Giardia lamblia and Entamoeba histolytica trophozoites. Materials and methods: Conventional cultures of parasites were measured on the third day during the logarithmic
growth phase. The antiprotozoal activity of the methanol extract and its fractions were evaluated comparing growth in cultures with and without extracts.
Next, the extract was fractionated by polarity-based partitioning. Then, the
purity of each fraction was determined by thin layer chromatography (TLC).
The percentage of growth inhibition was calculated with respect to untreated
controls. The 50% inhibitory concentration (IC50) of each extract was calculated by PROBIT analysis. Results: We found that a methanol extract of the
aerial parts of Thymus vulgaris, at 300 μg/mL, inhibited the in vitro growth of
G. lamblia and T. vaginalis, while E. histolytica growth was poorly inhibited.
The methanol extract was further separated into mixtures of ursolic, oleanolic,
and betulinic acids. The IC50 values of ursolic acid against G. lamblia and T.
vaginalis were 8.12 μg/mL and 5.51 μg/mL, respectively. Conclusions: The
methanol extract fraction containing ursolic acid obtained from Thymus vulgaris has antiprotozoal activity against G. lamblia and T. vaginalis trophozoites