Effect of browse species, storage conditions and Extraction solvents on concentration of extractable Condensed tannin and in vitro anti-haemonchus Contortus activity

Abstract

The study was carried out to evaluate effects of the selected indigenous tannin rich tree species, storage conditions and extraction solvents on concentration of extractable condensed tannins (ECT) and to quantify and compare the in vitro anthelmentic activity of the plant species at different storage time and extraction methods against Haemonchus contortus activity. Albizia gummifera, Carissa edulis, Ficus ovata, Maytenus obscura and Rhus glutinosa species suspected with high content of tannins were collected from their natural habitat in Omo Nada Woreda of Jimma Zone, South West Ethiopia. The plant species were subjected to extractable condensed tannin analysis. Fresh leaves, fresh leaves dried at 55 °C and ground immediately and the dried and ground plant materials that have been preserved for 1.5 years at room temperature were used. Two levels of aqueous acetone and ethanol, each having 50 and 70% v/v), were incorporated for the extraction of plant samples. The extracts were prepared to obtain 50 mg /ml concentrations and accompanied by controls: distilled water (negative control) and Albendazole (positive control). The inhibitory effects of ECT on egg hatchability, larvae development and adult mortality of Haemonchus contortus also studied. The data were subjected to a three ways analysis of variance following the general linear model procedure of statistical analysis system in a 5x4x3 factorial arrangement. Interspecies variations were significant for ECT concentration across the storage conditions (P<0.001). ECT concentration in dried and dried-preserved leaves of all the plants were found to be above the threshold value that affects nutrient value of feedstuffs (50 g/kg DM). ECT values obtained by both levels acetone tended to be higher than the values determined by ethanol 50 and 70%. Plant extracts induced anthelmintic effects on the three life-cycle stages of H.contortus and these effects were significantly different when they were compared to the positive and negative control group (P<0.001). All the plants showed anthelmintics activity in three-life cycle of the parasite. However, variations in the efficiency were observed depending on the storage conditions and plant species. The organic solvent that has high capacity to extract condensed tannins from livestock feeds would be better choices determining tannins. The potential bioactive substances used in vitro may not always correspond to in vivo bioavailability. Therefore, in vitro assays should always be accompanied by in vivo trials when used to validate anthelmintic activity of plant remedies