Anticholinesterase and acaricidal activities of steroids isolated from trianthema portulacastrum L. against Rhipicephalus annulatus tick

Abstract

The anticholinesterase and acaricidal activities of two plants of family Aizoaceae; Trianthema portulacastrum L. and Aizoon canariensis L. against Rhipicephalus annulatus tick were performed. Acaricidal activity was evaluated using adult and larval immersion tests of different concentrations (12.5, 25, 50, 100, and 150 mg/ml). Anti-acetylcholinesterase activity of plant extracts and isolated compounds were performed spectrophotometrically using different concentrations (0.25, 0.5, and 1 mg/ml). Trianthema portulacastrum crude hydroalcoholic (CH) extract showed 100% adult and larval mortality, while A. canariensis L. showed only 20% and 25%, respectively (p ≥ 0.05). The bioassay-guided fractionation of T. portulacastrum hydroalcoholic extract was performed for the acaricidal activity and both n-hexane fraction and the unsaponifiable matter (USM) retained a significant activity in immersion tests. Its column chromatography (CC) led to the isolation of a β-sitosterol (1)-stigmasterol (2) mixture (1:1). Ethyl acetate (EA) fraction showed 70% adult mortality and the compound 20-hydroxyecdysone (3) was isolated as a major compound. The hydroalcoholic extract of T. portulacastrum, hexane fraction, and 20-hydroxyecdysone (3) produced the most potent inhibitory effect on acetylcholinesterase (AChE). In conclusion, T. portulacastrum L. contains secondary metabolites with acaricidal activities that provide promising natural products for controlling bovine tick. These acaricidal effects may be mediated, at least in part, via AChE inhibitory activities.