Antifeedant Property and Physiological Effect of Total Alkaloids of Peganum harmala L. against Spodoptera litura F.

Total alkaloids extracts were isolated by the primary separation of ethanol extract of the seed of Peganum harmala (ESPH). Separation of chloroform fraction was performed through silica gel column; 16 fractions were isolated; the 4th and 14th fractions produced prisms. Bioactivity of all fractions were compared. The most active fraction were fraction 4, 12 and 14. The bioactivity test showed that fraction 4, 12 and 14 at 1 000 μg/mL possessed very high strong antifeedant property against the 3rd-instar larvae of Spodoptera litura in no-choice test, and the antifeedant rates were 96.04%, 92.07% and 100.00% after 24 h, and 98.82%, 96.05% and 98.08% after 48 h, respectively. Mechanism of three active fractions showed that active substance of P. harmala could disturb normal physiological function of insect. Against the 4th-instar larvae of S. litura, the protein content of haemolymph was significantly reduced in the larvae, and the total body sugar was reduced obviously when treated with the 12th and 14th fractions at 500 μg/mL.