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
