title: Synergistic inhibition of Haemonchus contortus exsheathment by flavonoid monomers and condensed tannins.
abstract: This study investigated the separate and combined anthelmintic (AH) effects of different phenolic compounds, including condensed tannins and flavonoids, all of which are known to occur in willow leaves, a potentially valuable dry season feed. A range of contrasting model tannins, which span the whole range of willow tannins, were isolated from tilia flowers, goat willow leaves, black currant leaves and red currant leaves. All together, the tested compounds represented the major tannin types (procyanidins and prodelphinidins) and flavonoid types (flavonols, flavones and flavanones). The larval exsheathment inhibition assay (LEIA) was used to assess their in vitro effects on Haemonchus contortus third stage larvae. Arbutin, vanillic acid, and taxifolin proved to be ineffective whereas naringenin, quercetin and luteolin were highly effective at 250 μM concentrations. Procyanidin (PC) tannins tended to be less active than prodelphinidin tannins (PD). Experiments with combinations of tannins and quercetin or luteolin revealed for the first time the existence of synergistic AH effects between tannins and flavonoid monomers. They also provided evidence that synergistic effects appear to occur at slightly lower concentrations of PC than PD. This suggests that the AH activity of condensed tannins can be significantly enhanced by the addition of quercetin or luteolin. This information may prove useful for plant breeding or selection and for designing optimal feed mixtures.
authors.affiliation: Chemistry and Biochemistry Laboratory, School of Agriculture, Policy and Development, University of Reading, P O Box 236, Reading RG6 6AT, UK.
authors.forename: Chaweewan
authors.initials: C
authors.lastname: Klongsiriwet
authors.affiliation: UMR IHAP 1225 INRA/ENVT, Ecole Nationale Veterinaire de Toulouse, 31076, 23 Chemin des Capelles, Toulouse Cedex, France.
authors.forename: Jessica
authors.initials: J
authors.lastname: Quijada
authors.affiliation: Faculty of Health and Medical Sciences, University of Copenhagen, 1871 Frederiksberg C, Denmark.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Williams
authors.affiliation: Chemistry and Biochemistry Laboratory, School of Agriculture, Policy and Development, University of Reading, P O Box 236, Reading RG6 6AT, UK.
authors.forename: Irene
authors.initials: I
authors.lastname: Mueller-Harvey
authors.affiliation: School of Pharmacy, P O Box 226, Whiteknights, Reading RG6 6AP, UK.
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Williamson
authors.affiliation: UMR IHAP 1225 INRA/ENVT, Ecole Nationale Veterinaire de Toulouse, 31076, 23 Chemin des Capelles, Toulouse Cedex, France.
authors.forename: Hervé
authors.initials: H
authors.lastname: Hoste
mesh_terms: D000818:Animals; D005419:Flavonoids / Q000737:chemistry / Q000494:pharmacology*; D006189:Haemonchus / Q000187:drug effects* / Q000502:physiology*; D007814:Larva / Q000187:drug effects / Q000502:physiology; D015394:Molecular Structure; D010944:Plants / Q000737:chemistry; D044945:Proanthocyanidins / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D005419:Flavonoids; D044945:Proanthocyanidins
keywords: Flavan-3-ols; Luteolin; Mean degree of polymerisation; Nematodes; Proanthocyanidins; Procyanidins; Prodelphinidins; Quercetin