In the present study, acute toxicity of methanolic root extract (MREt) of Rauwolfia serpentina (10-250 mg/kg) was observed in terms of hypoglycemic activity and behavior pattern including sedation and mortality rate in different groups of normoglycemic wister mice (6/group). Orally administrated MREt (10 to 60 mg/kg) was found non-sedative and showed hypoglycemic activity by reducing the mean blood glucose level from 80 to 62 mg/dL after 30 min of administration while the doses (100-250 mg/kg) of same extract showed sedation and mortality rate from 17 to 100% within 4 h. The value of median lethal dose (LD 50) of MREt of R. serpentina was 141.25 mg/kg (log LD50 = 2.15 mg/kg) from graph plotted between log-doses verses probits. In oral glucose tolerance test, MREt (10, 30 and 60 mg/kg) showed significant hypoglycemic activity at 0, 30 and 60 min by deceasing blood glucose level ranging from 31-65%, 39-49% and 25-51% respectively compared to control and negative control (treated with 0.05% dimethylsulfoxide @ 1 mL/kg) groups. However, MREt (100 mg/kg), though hypoglycemic from 0 to 120 min, induced slight sedation and mortality in experimental mice. The results indicated that the MREt (10-60 mg/kg) was non-sedative and effective in lowering the blood glucose level in mice but showed lethal effect in terms of sedation and mortality at doses ≥ 100 mg/kg. Therefore, MREt of R. serpentina in small doses can improve the glucose tolerance either at pancreatic or extra-pancreatic level.

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