Evaluation of physiological and biochemical effects of two Sophora alopecuroides alkaloids on pea aphids Acyrthosiphon pisum

Background: Sophora alopecuroides alkaloids are the main constituents for the broad bioactivities on insect pests, especially on aphids. However, the aphicidal mode of action of S. alopecuroides alkaloids remains unclear. To clarify the aphicidal action, avermectin was selected as a positive control, and matrine, sophocarpine were chosen as the representative alkaloids to determine the physiological and biochemical effects on pea aphids (Acyrthosiphon pisum).

Results: The aphids treated by matrine and sophocarpine developed the intoxication symptoms of convulsions, paralysis, and death. However, avermectin showed no convulsions. Moreover, the two alkaloids had a significant inducing effect on glutamic acid decarboxylase, and the specific enzyme activity was 1.14-1.22 times of the control group. In the meanwhile, both matrine and sophocarpine possessed a dose-response and time-response inhibitory effect on alanine aminotransferase in vivo and in vitro. Furthermore, the glutamate content in pea aphids treated with the two alkaloids increased significantly with time, which was about 1.5-2.0 times that of the control group. Similarly, the GABA content elevated significantly, with an increase of 1.0-1.3 times. In addition, all the treatments, except avermectin, presented inhibitory effects on Na⁺ , K⁺ -ATPase, Ca²⁺ and Mg²⁺ -ATPase, with dose-response and time-response effect. However, the three treatments had no significant effect on acetylcholinesterase and acetylcholine content.

Conclusion: The toxicological action of matrine and sophocarpine is related to the regulation on glutamate and γ-aminobutyric acid systems and has certain similarities to that of avermectin. These findings would provide a basis for further mechanism elucidation.

Keywords: Sophora alopecuroides; botanical pesticide; matrine; mode of action; pea aphid.