In Vitro Ovicidal Activity of Two Chemotypes of the Yarrow (Achillea millefolium L.) Essential Oil against Ovine Gastrointestinal Nematode Eggs

Abstract

Economic losses caused by the gastrointestinal nematodes of small ruminants have been on increase mainly due to the development of anthelmintic resistance. Therefore, researchers from all around the world are searching for new, alternative strategies to control these parasites. Being a valuable natural resource, medicinal plants and their products have emerged as a viable option. This study aimed to evaluate the in vitro ovicidal activity of two chemotypes of yarrow (Achillea millefolium L.) essential oil against ovine gastrointestinal nematode eggs. Nematode eggs obtained from the faeces of naturally infected sheep on two farms located in Southern Italy were subjected to the egg hatch test. On both farms, the coproculture examination identified the presence of species belonging to four genera of sheep gastrointestinal nematodes: Haemonchus, Trichostrongylus, Teladorsagia and Chabertia. The main components of the yarrow essential oil identified by GC-MS analysis were 1,8-cineole (41.69%), camphor (8.37%) and trans-chrysanthenyl acetate (4.90%) in the oil type 1 and β-pinene (28.53%), β-caryophyllene (18.71%) and 1,8-cineole (11.69%) in type 2. The in vitro ovicidal activity was evaluated at six oil concentrations (50, 12.5, 3.125, 0.781, 0.195 and 0.049 mg/mL), whereby the inhibitory effect of the essential oil on egg hatchability varied from 46.5-99.5% (type 1) and from 69.6-97.25% (type 2). All concentrations tested showed a significantly higher efficacy compared to the negative control (p<0.0001). The inhibitory effect on egg hatching was similar (p>0.05) to the positive control (98.0%) at concentrations of 50 mg/mL (99.5%), 12.5 mg/mL (98.0%) and 3.125 (95.25%) of the oil type 1, and at concentrations of 50 mg/mL (97.25%) and 12.5 mg/mL (90.0%) of the type 2. The obtained results suggested that the A. millefolium essential oil has high anthelmintic potential, especially the chemotype rich in 1,8-cineole and camphor, which requires confirmation in further in vivo studies.

Ekonomski gubici koje prouzrokuju gastrointestinalne nematode malih preživara u poslednje vreme rastu usled razvoja rezistencije na antihelmintike. Zbog toga istraživači širom sveta tragaju za novim, alternativnim strategijama za kontrolu ovih parazita. Kao dragocen prirodan resurs, lekovite biljke i njihovi proizvodi nametnuli su se kao moguća opcija. Cilj ovog istraživanja je bio utvrditi in vitro ovicidnu aktivnost dva hemotipa etarskog ulja hajdučke trave (Achillea millefolium L.) protiv jaja gastrointestinalnih nematoda ovaca. Jaja nematoda su izolovana iz fecesa prirodno inficiranih ovaca sa dve farme locirane u južnoj Italiji kako bi se sproveo test izleganja larvi (eng. egg hatch test). Na obe farme, koprokulturološkim ispitivanjima je utvrđeno prisustvo vrsta četiri roda gastrointestinalnih nematoda ovaca: Haemonchus, Trichostrongylus, Teladorsagia i Chabertia. Najzastupljenije komponente etarskog ulja hajdučke trave identifikovane GC-MS analizama bile su 1,8-cineol (41,69%), kamfor (8,37%) i trans-hrizantenil acetat (4,90%) u ulju tipa 1, odnosno β-pinen (28,53%), β-kariofilen (18,71%) i 1,8-cineol (11,69%) u tipu 2. In vitro ovicidna aktivnost je testirana u šest različitih koncentracija (50; 12,5; 3,125; 0,781; 0,195 i 0,049 mg/mL). Inhibitorni efekat etarskog ulja na izleganje jaja je varirao od 46,5-99,5% (ulje tipa 1), odnosno 69,6-97,25% (tip 2), dok je kod svih ispitivanih koncentracija efekat bio značajno veći u poređenju sa negativnom kontrolom (p<0.0001). Pored toga, inhibitorni efekat na izgleganje larvi je bio sličan (p>0.05) pozitivnoj kontroli (98,0%) pri koncentracijama 50 mg/mL (99,5%), 12,5 mg/mL (98,0%) i 3,125 mg/mL (95,25%) ulja tipa 1, odnosno pri koncentracijama od 50 mg/mL (97,25%) i 12,5 mg/mL (90,0%) kod tipa 2. Dobijeni rezultati ukazuju na to da etarsko ulje hajdučke trave, naročito tipa 1 koje je bogato 1,8-cineolom i kamforom, poseduje visok antihelmintički potencijal, što zahteva potvrdu u daljim in vivo ispitivanjima.