The antiprotozoal and antioxidant activities of Viola tricolor and Laurus nobilis have been reported recently. Thus, the existing study pursued to assess the growth inhibition effect of methanolic extract of V. tricolor (MEVT) and acetonic extract of L. nobilis (AELN) against five Babesia parasites and Theileria equi in vitro and in vivo.

MEVT and AELN suppressed Babesia bovis, B. bigemina, B. divergens, B. caballi, and T. equi growth at half-maximal inhibitory concentration (IC₅₀) values of 75.7 ± 2.6, 43.3 ± 1.8, 67.6 ± 2.8, 48 ± 3.8, 54 ± 2.1 μg/mL, and 86.6 ± 8.2, 33.3 ± 5.1, 62.2 ± 3.3, 34.5 ± 7.5 and 82.2 ± 9.3 μg/mL, respectively. Qualitative phytochemical estimation revealed that both extracts containing multiple bioactive constituents and significant amounts of flavonoids and phenols. The toxicity assay revealed that MEVT and AELN affected the mouse embryonic fibroblast (NIH/3 T3) and Madin–Darby bovine kidney (MDBK) cell viability with half-maximum effective concentrations (EC₅₀) of 930 ± 29.9, 1260 ± 18.9 μg/mL, and 573.7 ± 12.4, 831 ± 19.9 μg/mL, respectively, while human foreskin fibroblasts (HFF) cell viability was not influenced even at 1500 μg/mL. The in vivo experiment revealed that the oral administration of MEVT and AELN prohibited B. microti multiplication in mice by 35.1 and 56.1%, respectively.

These analyses indicate the prospects of MEVT and AELN as good candidates for isolating new anti-protozoal compounds which could assist in the development of new drug molecules with new drug targets.