Evaluation of bio efficacy of Tylophora indica leaf extracts, fractions and pure alkaloids against Helicoverpa armigera (Hubner)

Crude extracts, fractions and pure alkaloids from Tylophora indica (Burm. f.) Merrill were tested against Helicoverpa armigera larvae and moths. Among the extracts, ethanol extract was more effective than the hexane extract in reducing larval growth with GI50 value (concentration at which 50% reduction in larval weight obtained) of 0.031. Significant reduction in pupal weight was also observed (up to 20%). An average of 221.50 +/- 36.04, 191.25 +/- 17.50, 113.75 +/- 30.92, 42.50 +/- 14.43 at 0.25%, 0.50%, 1.0% and 2.0% concentration respectively compared to 345.00 +/- 54.46 eggs in control jar.

The alkaloids were better than ethanol extract in reducing growth (GI50 = 0.016% and 0.020%) and oviposition (up to 72% at 1.0%). Fractionation of ethanol extract by portioning with different solvents resulted in improved activity and fraction having GI50 of 0.0006%, 155 times better than the ethanol extract. Among the pure alkaloid tylophorinine was found to be the most active alkaloid with LC50 value of 7.1 ppm. The presence of a hydroxyl function on the indolizidine moiety increased the activity significantly and could be attributed to mortality in larvae.