Anthelminthic activity of methanol extracts of Diospyros anisandra and Petiveria alliacea on cyathostomin (Nematoda: Cyathostominae) larval development and egg hatching.

Methanol extracts of plant structures are promising alternatives to traditional pharmaceutical anthelminthic treatments. An in vitro evaluation was done of how methanol extracts of Diospyros anisandra bark and leaves, and Petiveria alliacea stems and leaves, collected during the rainy and dry seasons, effected cyathostomin larval development and egg hatching. Seven concentrations (600, 300, 150, 75, 37.5, 18.7 and 9.3µg/ml) were tested using the egg hatch assay. An ANOVA was applied to identify differences between the concentrations and the controls. Fifty percent lethal concentration (LC50) and the 95% confidence interval were calculated with a probit analysis. At and above 37.5µg/ml, the D. anisandra bark extracts from both seasons exhibited ≥95% egg hatch inhibition (EHI), while the D. anisandra leaf extracts had >90% EHI at and above 75µg/ml. For P. alliacea, the extracts from leaves and stems from either season exhibited >97% EHI at and above 300µg/ml, although similar efficacy was also observed at lower concentrations with the rainy season stems (75µg/ml) and leaves (150µg/ml). Values for LC50 were lowest for the rainy season D. anisandra bark (10.2µg/ml) and leaf extracts (18.4µg/ml), followed by the rainy season P. alliacea stems extract (28.2µg/ml). In the D. anisandra extracts, EHI was largely due to its ovicidal activity (≥96% beginning at 37.5µg/ml), whereas in the P. alliacea extracts it was due to L1 larval hatch failure (≥90% beginning at 75µg/ml). Overall, the rainy season D. anisandra bark extracts had a strong in vitro anthelminthic effect against cyathostomins by inhibiting larval development, and the rainy season P. alliacea stem extracts had a strong effect by preventing egg hatching. Both are possible control alternatives for these nematodes.

Plant products and secondary metabolites with acaricide activity against ticks.

The present review documents the results of studies evaluating the acaricidal activity of different plant products and secondary metabolites against ticks that are resistant and susceptible to conventional acaricides. Studies published from 1998 to 2016 were included. The acaricidal activity of plant extracts, essential oils and secondary compounds from plants have been evaluated using bioassays with ticks in the larval and adult stages. There is variable effectiveness according to the species of plant and the concentrations used, with observed mortalities ranging from 5 to 100% against the Rhipicephalus (Boophilus), Amblyomma, Dermacentor, Hyalomma, and Argas genera. A number of plants have been reported to cause high mortalities and/or affect the reproductive capacity of ticks in the adult phase. In the majority of these trials, the main species of plants evaluated correspond to the families Lamiaceae, Fabaceae, Asteraceae, Piperaceae, Verbenaceae, and Poaceae. Different secondary metabolites such as thymol, carvacrol, 1,8-cineol and n-hexanal, have been found to be primarily responsible for the acaricidal activity of different essential oils against different species of ticks, while nicotine, dibenzyldisulfide and dibenzyltrisulfide have been evaluated for plant extracts. Only thymol, carvacrol and 1,8-cineol have been evaluated for acaricidal activity under in vivo conditions. The information in the present review allows the conclusion that the secondary metabolites contained in plant products could be used as an alternative for the control of ticks that are susceptible or resistant to commercial acaricides.