Acute toxicity studies
Experimental procedure and handling of animals
was carried out according to the OECD testing
guidelines [39]. One measure of acute toxicity is the lethal dose 50 (LD50), i.e., the dose of a
substance that kills 50 % of the animals tested. The animals (n = 6) were treated with a single
dose of 5000 mg/kg ofMentha spicata extract by oral gavage (with the volume of 10 ml/kg body
weight of the rats) after overnight fast. The
control group received only the vehicle (0.5 % Tween 80).
Utmost care was taken to avoid the entry of the gavage to the breathing system of
the rats during the gavage feeding. After the extract was administered, feed but not water was
withheld for 3-4 h and the animals was
monitored for 14 days. Mortality rate and body weight were recorded weekly. At the end of the experiment, the rats were anesthetized using diethyl ether and blood was drawn using direct
cardiac puncture. At the end of the experiment, the rats were anesthetized using diethyl ether,
sacrificed by cervical dislocation, and subjected to gross necropsy and dissection. Major vital
whole organs (liver, kidney, heart, spleen and lungs) were removed and stored in formalin
pending histopathological studies.