In vitro screening of forty medicinal plant extracts from the United States Northern Great Plains for anthelmintic activity against Haemonchus contortus

An egg hatch assay (EHA) and a larval migration assay (LMA) involving Haemonchus contortus was used to evaluate the anthelmintic activity of methanol extracts from 40 plants that are native or naturalized within the U.S.A. Northern Great Plains. Only one of these 40 plants (i.e. Lotus corniculatus) had been previously evaluated for activity against any gastrointestinal nematode. The various extracts were initially screened at 50 mg/ml diluted either in 0.5% dimethyl sulphoxide (DMSO) or 3-(N-morpholino) propanesulfonic acid (MOPS buffer), and plants showing 100% inhibition at 50 mg/ml, were further evaluated at 8 other concentrations (25-0.19 mg/ml). Extracts with 100% activity with the EHA were again screened with the LMA (50 mg/ml). Two extracts with the highest LMA inhibition were also evaluated at lower concentrations (25-3.1 mg/ml). Of the 40 methanolic extracts screened, 7 (Chrysothamnus viscidiflorus, Ericameria nauseosa, Liatris punctata, Melilotus alba, Melilotus officinalis, Perideridia gairdneri, and Sanguinaria canadensis) showed significant egg-hatch inhibition in DMSO and MOPS buffer. Three extracts (Geranium viscosissimum, L. corniculatus, and Rhus aromatica) only showed significant inhibition in DMSO. The 8 extracts showing 100% efficacy at 50 mg/ml exhibited dose-dependent effects at the 8 lower concentrations, and R. aromatica and E. nauseosa extracts had the lowest ED50 values. Similarly, when these 8 plant extracts were further evaluated with the LMA, the extracts of E. nauseosa and R. aromatica again exhibited the highest activity (p < 0.001), with ED50 values of 4.0 mg/ml and 10.43 mg/ml respectively. Three other extracts (C. viscidiflorus, M. alba and M. officinalis) also showed inhibitory activity in the LMA. These results support the need for additional evaluations of the nematocidal properties for at least these 5 plants.