Chemical composition, in vitro antioxidant and antiparasitic properties of the essential oils of three plants used in traditional medicine in Benin

Sclerocarya birrea (Sb), Psidium guajava (Pg) and Eucalyptus camaldulensis (Ec) are widely used in traditional medicine for the treatment of many diseases, some of which were related to oxidative stress and parasitic diseases. Their essential oils (EO) were analyzed by GC/MS and FID and tested in vitro for their antioxidant activities (DPPH), their anti-trypanosomal and anti-plasmodial activities against Trypanosoma brucei brucei (Tbb) (strain 427) and Plasmodium falciparum (Pf) (strain 3D7), respectively. Cytotoxicity was evaluated in vitro against CHO and WI38 cells (MTT) to evaluate the selectivity. They were shown to possess low antioxidant but a strong anti-trypanosomal and a good antiplasmodial activity with a good selectivity, except Ec oil whose anti-plasmodial activity was less interesting. Sb oil was the most active against Tbb(IC50 = 0.46 ± 0.28 µg/ml) and Pf (5.21 ± 1.12 µg/ml). All tested oils had low or no cytotoxicity against CHO and WI38 cells. GC/MS and GC/FID analysis revealed that composition of Sb (49 compounds) was characterised by the presence as main constituents of 7-epi-α-selinene, α-muurolene and valencene; Pg (60 compounds) by β-bisabolene, ar-curcumene and β-bisabolol; Ec (43 compounds) by γ-terpinene and p-cymene. The activity of these oils seems to be the result of a synergistic action of all their constituents, including minor ones. This study shows that essential oils of Sb and Pg can be good sources of anti-trypanosomal and anti-plasmodial agents. Key words: Essential oil, S. birrea, P. guajava, E. camaldulensis, antimalarial, antitrypanosomal, antioxidant.