In vitro ovicidal effect of a Senecio brasiliensis extract and its fractions on Haemonchus contortus

Abstract

Background: Haemonchosis affects sheep husbandry and its treatment is often compromised due to the development of anthelminthic resistance. Plant-derived bioactive compounds have been studied as alternative to control Haemonchus contortus. The objective of this study was to evaluate the effect of Senecio brasiliensis extracts on H. contortus egg hatching and infective larvae migration.

Results: The aqueous extract from dried and fresh plant and alkaloid-enriched fraction of the previously dried leaves of S. brasiliensis inhibited H. contortus egg hatching. The main plant compound in alkaloid fraction was integerrimine, a pyrrolizidine alkaloid (PA). However, the aqueous extract from dried plant displayed higher efficacy when compared to their alkaloid enriched or non-polar fractions, meaning that, although PAs contributed to the ovicidal effect, other compounds in the plant can also contribute to their effect. Furthermore, the aqueous extract from dried plant also had higher efficacy than aqueous extract from fresh plant in larvae migration inhibition. Finally, extract from dried plant presented low in vitro cytotoxic effect.

Conclusion: Taken together our results suggest a good anthelmintic effect of S. brasiliensis, especially when aqueous extract is prepared from dried plant. Further in vivo studies should be performed focused on forms of administration of this extract in rearing sheep.

Keywords: Anthelmintic; Egg hatching; Infective larvae migration; Plant extract; Pyrrolizidine alkaloids; Small ruminants.

Fig. 1

Optical microscopy of eggs and hatched larvae: representative image of H. contortus eggs with larva failing eclosion (white arrow) and larva (black arrow). Eggs were treated with dried plant extract during 24 h. 100x magnification

Fig. 2

Effect of Senecio brasiliensis extracts on Haemonchus contortus egg hatching inhibition: a Dried plant extract (DP); b Fresh plant extract; c Alkaloid fraction of DP extract; d Non-polar fraction of DP extract. Different letters mean difference between groups (p < 0.05; one-way ANOVA followed by Tukey’s post-hoc test)

Fig. 3

Effect of Senecio brasiliensis extracts on Haemonchus contortus larval migration inhibition: a Dried plant extract; b Fresh plant extract. Different letters mean difference between groups (p < 0.05; one-way ANOVA followed by Tukey’s post-hoc test)

Fig. 4

Cytotoxic effect of dried Senecio brasiliensis extract on Vero cells. Different letters mean difference between groups (p < 0.05; one-way ANOVA followed by Tukey’s post-hoc test)