Abstract
Thymol is a monoterpene and acetylation form of this compound can reduce the toxicity and enhance its biological effects. The objective of this study was to evaluate the effect of thymol and thymol acetate (TA) on egg, larva and adult Haemonchus contortus and the cuticular changes, acute toxicity in mice and the efficacy on sheep gastrointestinal nematodes. In vitro tests results were analyzed by analysis of variance (ANOVA) and followed by comparison with Tukey test or Bonferroni. The efficacy of in vivo test was calculated by the BootStreet program. In the egg hatch test (EHT), thymol (0.5 mg/mL) and TA (4 mg/mL) inhibited larval hatching by 98% and 67.1%, respectively. Thymol and TA (8 mg/mL) inhibited 100% of larval development. Thymol and TA (800 µg/mL) reduced the motility of adult worms, by 100% and 83.4%, respectively. Thymol caused cuticular changes in adult worm teguments. In the acute toxicity test, the LD50 of thymol and TA were 1,350.9 mg/kg and 4,144.4 mg/kg, respectively. Thymol and TA reduced sheep egg count per gram of faeces (epg) by 59.8% and 76.2%, respectively. In in vitro tests thymol presented better anthelmintic activity than TA. However TA was less toxic and in in vivo test efficacy was similar.
Highlights
Gastrointestinal nematodes, especially Haemonchus contortus, cause economic losses in sheep and goat production worldwide (PERRY & RANDOLPH, 1999; MARIE-MAGDELEINE et al, 2010; QI et al, 2015)
The effect of these oils is associated with its biocomposites that act in synergism and that interact with multiple molecular targets during various stages of nematode development, interfering with their biochemical and physiological functions (MACEDO et al, 2013; NORDI et al, 2014)
Considering the potential use of bioactive compounds that are isolated from essential oils in the control of helminths, the aim of this study was to evaluate the anthelmintic effect of thymol and thymol acetate (TA) on sheep gastrointestinal nematodes and to evaluate their toxicity in mice
Summary
Gastrointestinal nematodes, especially Haemonchus contortus, cause economic losses in sheep and goat production worldwide (PERRY & RANDOLPH, 1999; MARIE-MAGDELEINE et al, 2010; QI et al, 2015) This nematode causes weight loss, decreases milk production, and reduces fertility, and may lead to death in cases of high infection (BESIER et al, 2016). Essential oils are among the class of natural products that have anthelmintic activity and may be an alternative treatment for the control of gastrointestinal nematode infection of small ruminants (RIBEIRO et al, 2014) The effect of these oils is associated with its biocomposites that act in synergism and that interact with multiple molecular targets during various stages of nematode development, interfering with their biochemical and physiological functions (MACEDO et al, 2013; NORDI et al, 2014)
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