Abstract
The objective of this study was to evaluate the effects of protein extracts obtained from the plant Leucaena leucocephala on the nematode parasite Haemonchus contortus. The seeds, shell and cotyledon of L. leucocephala were separated and their proteins extracted using a sodium phosphate buffer, and named as TE (total seed extract), SE (shell extract) and CE (cotyledon extract). Soluble protein content, protease, protease inhibitory and chitinase activity assays were performed. Exsheathment inhibition of H. contortus larvae were performed at concentrations of 0.6 mg mL-1, and egg hatch assays were conducted at protein concentrations of 0.8, 0.4, 0.2, 0.1 and 0.05 mg mL-1. The effective concentration for 50% hatching inhibition (EC50) was estimated by probit. Different proportions of soluble proteins, protease and chitinase were found in TE and CE. Protease inhibitory activity was detected in all extracts. The EC50 of the CE and TE extracts were 0.48 and 0.33 mg mL-1, respectively. No ovicidal effects on H. contortus were detected in SE extracts, and none of the protein extracts demonstrated larvicidal effects on H. contortus. We therefore conclude that protein extracts of L. leucocephala had a detrimental effect on nematode eggs, which can be correlated with the high protease and chitinase activity of these extracts.
Highlights
Infections with gastrointestinal nematodes are a primary cause of the loss of small ruminant livestock (HOUNZANGBEADOTE et al, 2005; CEZAR et al, 2008)
We conclude that protein extracts of L. leucocephala had a detrimental effect on nematode eggs, which can be correlated with the high protease and chitinase activity of these extracts
This study aims to examine the anthelmintic activity of protein extracts of L. leucocephala on the gastrointestinal nematode H. contortus and to verify the activities of some proteins that could be related to the bioactivity of the extracts against this parasite
Summary
Infections with gastrointestinal nematodes are a primary cause of the loss of small ruminant livestock (HOUNZANGBEADOTE et al, 2005; CEZAR et al, 2008). The nematode Haemonchus contortus is considered the most important because. Plants have a variety of defense and protection response mechanisms (SHARMA et al, 2011). Anthelmintic activity of L. leucocephala protein extracts on H. contortus function is to both store nutrients for germination and growth and act as defense proteins against pathogens, especially proteases, protease inhibitors, and chitinases (CARLINI & GROSSI-DE-SÁ, 2002). It is thought that proteases and chitinases may be have potential nematicidal properties because of their ability to break down important macromolecules that constitute the cuticle of these parasites. Nematodes feature a morphologically complex cuticle composed of resistant proteins such as collagen, which functions as a protective barrier between the parasite and the external environment (SHAMANSKY et al, 1989; RHOADS & FETTERER, 1990). The cuticle of H. contortus eggs has three layers: an internal layer composed of lipids with some associated proteins; an intermediate layer composed of chitin fibers surrounded by proteins; and an outer layer composed of proteins and lipids (MANSFIELD et al, 1992)
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