Hydrolyzable tannins fighting gastrointestinal parasites of ruminants: chemical structure predicts in vitro anthelmintic activity

The use of synthetic drugs against gastrointestinal nematodes of ruminants has led to a situation where resistance to anthelmintics is widespread and there is an urgent need for alternative solutions for parasite control. One promising approach is to use polyphenol-rich bioactive plants in animal feeds as natural anthelmintics [1]. In the present work, the in vitro activity of a series of 33 hydrolyzable tannins (HTs) and their hydrolysis product, gallic acid, against egg hatching and motility of L1 and L2 stage Haemonchus contortus larvae was studied [2]. The effect of the selected compounds on egg and larval structure was further studied by scanning electron microscopy. The in vitro anthelmintic activities of the studied compounds varied between 0% and 100%, depending on the compound and the concentration. The overall results indicated clear relationships between HT structure and in vitro anthelmintic activity (Fig. 1A). Furthermore, the structure-activity comparisons resulted in an equation that enable the prediction of the activities of yet non-studied compounds based on their structural features (Fig. 1B). While HT size, overall flexibility, the types and numbers of functional groups together with the linkage types between monomeric HTs affected the activity differently, the optimal structure was found with pentagalloylglucose.

Fig. 1: The average inhibition activities of the studied hydrolyzable tannins in egg hatch assay (EHA) (A) and the correlation between the measured and the calculated average egg hatching inhibitory activities tannins against Haemonchus contortus (B).

Acknowledgements: Sanjib Saha, Jussi Suvanto, Milla Leppä, Jessica Quijada, Israel Chan Pérez, Elodie Gaudin, Ramzi El Korso and Liza Fonsou are acknowledged for assistance.

Keywords: bioactive plant, polyphenol, tannin, hydrolyzable tannin, nematode, Haemonchus contortus, natural anthelmintic, SEM.

References:

[1] Hoste H, Torres-Acosta JFJ, Sandoval-Castro CA, Mueller-Harvey I, Sotiraki S, Louvandini H, Thamsborg SM, Terrill TH. Tannin containing legumes as a model for nutraceuticals against digestive parasites in livestock. Vet Parasitol 2015; 21: 5 – 17

[2] Engström MT, Karonen M, Ahern JR, Baert N, Payré B, Hoste H, Salminen JP. Chemical structures of plant hydrolyzable tannins reveal their in vitro activity against Egg hatching and motility of Haemonchus contortus nematodes. J Agric Food Chem 2016; 64: 840 – 851

No conflict of interest has been declared by the author(s).