The use of tannin-rich plants against gastro-intestinal nematodes is an alternative currently investigated to avoid the exclusive use of anthelmintic (AH) synthetic drugs and prevent the spread of resistance among these nematode populations. Studies of AH effects on cattle nematodes using tannin-rich legumes such as Onobrychis viciifolia have been carried out in vitro but the contribution of all structural parameters from their condensed tannins has not been yet completely elucidated.
The aim of this study was to investigate the relationship between structure and AH activity in vitro. A series of condensed tannins extracts and fractions from various plants was chosen according to their monomeric composition (prodelphinidin/procyanidin ratio) and also characterised for their degree of polymerisation (mDP) and cis/trans ratio by thiolytic degradation. These tannins have been examined for their AH activity using the Larval Feeding Inhibition Assay (LFIA) and the Larval Exsheathment Inhibition Assay on Cooperia oncophora.
Preliminaries results with the LFIA showed that high AH activity was due to tannins with increasing prodelphinidin/procyanidin and cis/trans ratios. The variation in mDP between plants was very limited and the influence on AH activity could not be assessed. These findings should be confirmed with further in vitro assays including others tannin fractions. Furthermore, hazelnut skin crude extract presented a total inhibition of larval exsheathment at 600 µg/ml suggesting that some agro-industrial resources could likewise be helpful in sustainable control of cattle nematodes.