RESUMO
This study evaluated the depressant effects V. doniana stem bark ethanolic extract. The stem bark of V. doniana (2kg) was macerated for five days with 95% ethanol, filtered and evaporated in vacuo and the extracts concentrate yields was calculated to be 14.8%w/w. The intraperitoneal LD50 in rats estimated with 95% confidence limit was 2154.06mg/kg while no mortality was recorded with the oral route even on administration of 5000mg/kg extract. Thus the extract can be administered with a certain degree of safety. Pre-liminary phytochemical analysis was conducted to ascertain the primary and secondary metabolites present in the extract using standard procedures. The results revealed the presence of tannins, phlobatannins, saponins, carbohydrates, cardioactive glycoside, flavonoids, steroids and terpenes. Alkaloids and anthracenosides were absent in the extract. The administration of doses of 50 mg/mL and 100 mg/mL of the extract produced 70% and 80% local anesthesia respectively on rabbits. Xylocaine exerted local anesthetic effect of 35% and 50% at a concentration of 0.3 and 1.0 mg/ml respectivel. The result shows that the extract has significant (P< 0.01) local anesthetic effect when compared to xylocaine. Antinociceptive activity of the ethanolic extract was evaluated using acetic acid induced pain and heat. The extract demonstrated significant antinociceptive activities dose dependently when compared to control .The activity being more pronounced at highner dose of 600mg/kg which gave the high percentage protection of the abdominal constriction induced by acetic acid . About 80 and 100% of the treated rats with 400mg/kg and 600mg/kg of the extracts slid down the board. Effect of the extract of pentobarbitone sleep time in Albino Wister rats was also evaluated. The ethanolic stem bark extract of V. doniana increase the sleeping time together with the pentobarbitone from 72.3±3.07 at a doses(100mg/kg of extract and 35 mg/kg of the pentobarbitone) to 181±0.35 at a dose of 400mg/kg and 35 mg/kg) respectively.