The antihelminthic activity of methanolic extracts of leaf, stembark and root of Azadirachtaindica were evaluated in vitro againstHaemonchuscontortus larvae. Phytochemical screening conducted on the extracts of all the plant parts revealed the presence of carbohydrates, cardiac glycoside, saponins, flavonoids, tannins and alkaloids, leaf had steroids, while stembark and root had triterpenes. The quantitative estimation of the phytochemical constituents revealed a high percentage in flavonoids followed by alkaloids and tannins with least quantitative percentages insaponins: 20.21, 27.50, 20.95; 5.25, 5.48, 5.48; 4.95, 4.93, 4.15 and 0.75, 0.68, 0.67respectively. Eggs of H.contortus were cultured in culture plates maintained at 27°C in an incubator. The infective third stage larvae (L3) were recovered from 7-9 day old sterilefaecal cultures. The larvae harvested were concentrated at 1000 rpm for 15 minutes, 0.1 ml of the larvae containing 120 L3 were put into wells of microtitre plate and concentrations of each of the extracts (leaf, stembark and root) at 0.1mg/ml, 1.0mg/ml, 10.0mg/ml, 100mg/ml, negative control (water) and positive control (Levamisole) were added to each of the wells with six replication. After addition of the treatments, it was viewed under the microscope once in 6 hours for a period of 48 hours and the number of mortality recorded. The lethal concentration (LC50/ EC) value for the leafis 12.30mgml 1,12.58mgml-1 for the stem bark and 15.84mgml-1 for the root extract. Mortalities of the parasites increased with increase in the concentration and with the time of exposure. At the peak time of exposure (48 hours) and at the highest concentration of 100mgml-l, mortalities were higher than those of the least time of exposure (6 hours) and with the lowest concentration of 0.1mgml-1. The data showed highly significant differences between the plant parts, time of exposure, concentration of the extracts, the time of exposure and concentration and between the plant parts and concentration (p=0.001). Although, mortality of the parasites increased with increase in time, there were no significant differences between the plant parts and the time of exposure (p=0.92) and between the plant parts, time of exposure and concentration (p=0.99).Mortalities recorded were high in the positive control wells with increase in mortality as the time of exposure increased but in the negative control wells, mortalities were not recorded. The study concludes that mortalities recorded were due to the effects of the extracts on the parasites. Validation of the efficacy of the extracts of this plant is suggested to determine the effects of natural or experimental haemonchosis in ruminants.
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