<i>In vitro</i> anthelmintic activity of an aqueous extract of <i>Glycyrrhiza glabra</i> and of glycyrrhetinic acid against gastrointestinal nematodes of small ruminants
Michela Maestrini, Marcelo Beltrão Molento, Mario Forzan, Stefania Perrucci
Abstract
This study evaluated the in vitro anthelmintic activity of a liquorice ( Glycyrrhiza glabra ) root aqueous extract and of glycyrrhetinic acid at 30, 10, 5, 1, and 0.5 mg/mL against sheep gastrointestinal nematodes (GINs), using the egg hatch test (EHT), the larval development test (LDT), and the larval migration inhibition test (LMIT). The compounds were applied on a mixture of GIN eggs and larvae, mainly Trichostrongylus spp. and Teladorsagia/Ostertagia spp. Cytotoxicity assays were also performed. In the EHT, both candidates showed significant concentration-dependent efficacy and were significantly more effective ( p < 0.001) at the highest concentrations (30 and 10 mg/mL) than the lowest ones. In the LDT, only G. glabra showed a concentration-dependent effect ( R 2 = 0.924), but glycyrrhetinic acid ( R 2 = 0.910) had significantly higher efficacy than G. glabra root extract. Moreover, the efficacy of glycyrrhetinic acid at 30, 10, and 5 mg/mL was significantly higher ( p < 0.001) than at lower concentrations. In the LMIT, G. glabra showed concentration-dependent efficacy ( R 2 = 0.971), while considerably reduced efficacy was observed for glycyrrhetinic acid ( R 2 = 0.855) at the lowest concentrations. These data suggest that the two compounds may have different mechanisms of action. In the LMIT, the 50% lethal concentration (LC 50 ) of glycyrrhetinic acid (~5.12 mg/mL) was > 2.0-fold lower when compared to G. glabra (12.25 mg/mL). Analysis and previous findings indicated low toxicity for both compounds. The results obtained encourage in vivo studies aimed at evaluating the potential use of the tested compounds as natural de-wormers in ruminants.