Assessment of the anthelmintic activity of medicinal plant extracts and purified condensed tannins against free-living and parasitic stages of Oesophagostomum dentatum

Abstract

BackgroundPlant-derived condensed tannins (CT) show promise as a complementary option to treat gastrointestinal helminth infections, thus reducing reliance on synthetic anthelmintic drugs. Most studies on the anthelmintic effects of CT have been conducted on parasites of ruminant livestock. Oesophagostomum dentatum is an economically important parasite of pigs, as well as serving as a useful laboratory model of helminth parasites due to the ability to culture it in vitro for long periods through several life-cycle stages. Here, we investigated the anthelmintic effects of CT on multiple life cycle stages of O. dentatum.MethodsExtracts and purified fractions were prepared from five plants containing CT and analysed by HPLC-MS. Anthelmintic activity was assessed at five different stages of the O. dentatum life cycle; the development of eggs to infective third-stage larvae (L3), the parasitic L3 stage, the moult from L3 to fourth-stage larvae (L4), the L4 stage and the adult stage.ResultsFree-living larvae of O. dentatum were highly susceptible to all five plant extracts. In contrast, only two of the five extracts had activity against L3, as evidenced by migration inhibition assays, whilst three of the five extracts inhibited the moulting of L3 to L4. All five extracts reduced the motility of L4, and the motility of adult worms exposed to a CT-rich extract derived from hazelnut skins was strongly inhibited, with electron microscopy demonstrating direct damage to the worm cuticle and hypodermis. Purified CT fractions retained anthelmintic activity, and depletion of CT from extracts by pre-incubation in polyvinylpolypyrrolidone removed anthelmintic effects, strongly suggesting CT as the active molecules.ConclusionsThese results suggest that CT may have promise as an alternative parasite control option for O. dentatum in pigs, particularly against adult stages. Moreover, our results demonstrate a varied susceptibility of different life-cycle stages of the same parasite to CT, which may offer an insight into the anthelmintic mechanisms of these commonly found plant compounds.

Tannin containing legumes as a model for nutraceuticals against digestive parasites in livestock

“…compound structures) can also modulate the bioactivity. Recent data obtained with GIN models from cattle, small ruminants, and pigs (Novobilský et al, 2011(Novobilský et al, , 2013Quijada et al, 2015;Williams et al, 2014a) lend support to the hypothesis first raised by Molan et al (2003a) that bioactivity is linked to the prodelphinidin/procyanidin (PD/PC) ratio in plants. These recent studies have also revealed that tannin size is an important structural feature that contributes to the extent of the AH effects.…”

Benefits of Condensed Tannins in Forage Legumes Fed to Ruminants: Importance of Structure, Concentration, and Diet Composition

“…An important constraint in the quest for valid tannin data is the requirement for high purity standards for quantitation, which means that the CT concentration and purity of the standards needs to be assessed by CT-specific methods such as thiolysis (Gea et al, 2011;Grabber et al, 2013;Williams et al, 2014a) or nuclear magnetic resonance spectroscopy (Zeller et al, 2015a). We emphasize that the widely used elution of plant extracts with 70% aqueous acetone from Sephadex LH-20 columns for tannin "purification" can lead to CT concentrations as low as ~13 g CTs 100 g −1 "purified sample" (Williams et al, 2014b). Their use would overestimate CT concentrations, so additional steps are required to increase their purity Fryganas, 2016;Brown et al, 2017;Ropiak et al, 2017).…”

Structure–Activity Relationship of Condensed Tannins and Synergism with trans-Cinnamaldehyde against Caenorhabditis elegans

“…Condensed tannin (CT) content; mean degree of polymerization (mDP); molar percentages of: procyanidin, cis-flavan-3-ols and galloylation in fractions from various plant materials and estimated effective concentration of CT to reduce C. elegans motility by 50% (EC50). CT 0.45 -1 Note: data are presented for clarity purposes and literature references are provided, F2fraction 2, F3fractions 3; CT content has been reported 37 (calculated with mass response factor calculations); ( a ) data have been corrected for CT content (CT g/100 g of fraction); (n) number of independent experiments (composed of triplicate measurements at each CT concentration treatment); (nd) not detected; (-) not determined. Standard deviation in parentheses.…”

“…C. elegans has been used in pharmacological studies of synthetic AH drugs, 31 natural products [32][33][34][35] and even highthroughput screening. 36 Studies on the AH properties of CT against adult GIN are scarce 21,37,38 and culturing of adult C. elegans allowed us to avoid the sacrifice of experimental ruminants or monogastric animals. We screened nematocidal activity of CT in purified fractions derived from model plant materials.…”