Nematicidal Activity of alpha -Chaconine: Effect of Hydrogen-ion Concentration.

alpha-Chaconine, a steroid-glycoalkaloid from Solanum tuberosum L., was increasingly more toxic to a free-living nematode, Panagrellus redivivus, with decreasing acidity from about pH 5 to 7. A study of the toxicity to adult nematodes at three concentrations of alpha-chaconine in buffer from pH 4 to 7.5 indicated that the free base is the nematicidal form of the compound. The median effective doses (ED) of alpha-chaconine to inhibit the motility of P. redivivus were estimated as 85 mug/ml at pH 6.7, 170 mug/ml at pH 6.5, and 340 mug/ml at pH 6.2.