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 evaluatedusing adult and larval immersion tests of different concentrations (12.5, 25, 50, 100, and 150 mg/ml). Antiacetylcholinesterase activity of plant extracts and isolated compounds were performed spectrophotometrically usingdifferent concentrations (0.25, 0.5, and 1 mg/ml). Trianthema portulacastrum crude hydroalcoholic (CH) extractshowed 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 acaricidalactivity and both n-hexane fraction and the unsaponifiable matter (USM) retained a significant activity in immersiontests. Its column chromatography (CC) led to the isolation of a β-sitosterol (1)-stigmasterol (2) mixture (11). Ethylacetate (EA) fraction showed 70% adult mortality and the compound 20-hydroxyecdysone (3) was isolated as a majorcompound. The hydroalcoholic extract of T. portulacastrum, hexane fraction, and 20-hydroxyecdysone (3) producedthe most potent inhibitory effect on acetylcholinesterase (AChE). In conclusion, T. portulacastrum L. containssecondary 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.