Determination of median lethal dose (LD50)

Five groups of six rats each received volatile oil in doses ranging from 1 to 4 g/kg body weight. The toxic symptoms, mortality rate, and postmortem findings in each group were recorded 24 h after administration. The LD₅₀ of the tested extract was calculated according to the following formula:

where, D_m means the largest dose that kills all animals; z means the mean of dead animals between two successive groups; d means the constant factor between two successive doses; N means the number of animals in each group; ∑ means the sum of z × d. One fifth, one tenth and one twentieth of the maximum dose (5 g/kg body weight) of the plant extract that did not cause mortalities or toxic symptoms in rats were chosen to be used for the biological investigation throughout the study.