Chemical analyses and evaluation of the anthelmintic effects of Origanum majorana essential oil, in vitro and in vivo studies

Because of the development of resistance in helminths against major anthelmintic drugs, the search for alternatives is necessary. Medicinal plants are being studied as an alternative source of anthelmintics against gastrointestinal nematodes. The objective of this study is to analyse the chemical composition and evaluate the anthelmintic efficacy of Origanum majorana essential oil. The determination of the chemical composition by gas chromatography/mass chromatography (GC/MS) revealed that the essential oil was dominated by terpenoids, particularly carvacrol (35.65%) and terpenic hydrocarbons p-cymene (15.82%). The in vitro anthelmintic effects against Haemonchus contortus were assessed by an egg hatch assay (EHA) and an adult worm motility assay (AWMA) compared with the reference drug albendazole. The essential oil showed ovicidal activity at all the tested concentrations (1, 2, 4 and 8 mg/ml) and more than 80% egg hatching inhibition was observed at the highest dose (8 mg/ml). Exposure to 0.5 mg/ml of the essential oil for eight hours induced a 50% inhibition in the worm motility. The in vivo study was performed on H. polygyrus by measuring the egg count reduction (ECR) and adult worm count reduction (AWCR) following the treatment of the animals with different doses (2 000, 4 000 and 5 000 mg/kg) of the plant essential oil, and 22 mg/kg of albendazole as the positive control. The results showed that 5 000 mg/kg of the essential oil inhibited the egg count and adult worm count by 76.3 and 74.0%, respectively, seven days post treatment. These findings support the possible use of O. majorana essential oil to control gastrointestinal nematodes.