Comparative Nematocidal Activity of Chromatographic Fractions of Leucaena leucocephala. Seed Against Gastrointestinal Sheep Nematodes

Abstract

The anthelmintic effect of chromatographic fractions of leucaena leucocephala. (Lam.) de wit seed extract was investigated to determine the relative efficacy of the seed components as anthelmintic against gastrointestinal sheep nematodes. The fractions were obtained by thin-layer chromatographic (TLC) fingerprinting of eluates from gradient vacuum liquid chromatography (VLC) of the seed ethanol extract. These were evaluated for nematocidal activity by a larval development viability assay (LDVA) in vitro.. The effect of the test extracts on the transformation of L₁ to L₃ and the survival rate of infective larvae (L₃), of strongyles of sheep, predominantly Haemonchus contortus. (Rudolphi), was used to determine relative bioactivity. Best-fit LC₅₀ values were computed using global model of nonlinear regression curve-fitting. The composition of the fractions was identified by phytochemical screening. The extracts killed infective larvae of H. contortus. of sheep in a concentration-dependent manner. Best-fit LC₅₀ values are 77.66, 65.56, 56.72, and 40.80 µg/ml for fractions A, B, C, and D, respectively (95% CI). The fractions are composed of alkaloids (A), alkaloids and tannins (B and C), and flavonoids and tannins (D). Fraction D was significantly more active than all the other fractions (p < 0.001, one-way ANOVA, Tukey's multiple comparison test). The most active fraction (D) contains polar polyphenols, thus providing a scientific justification for the use of aqueous extract in traditional practice. The polyphenol fraction of L. leucocephala. seed could find application in anthelmintic therapy in veterinary practice.

Keywords:

• Chromatographic fractions
• Haemonchus contortus
• Leucaena leucocephala. seed
• Nematocidal activity