Molecular and biochemical characterization of the effects of insecticidal toxin from meloidae beetles on Helicoverpa armigera (Hub.) (Lepidoptera: Noctuidae)

Abstract

ABSTRACT. The molecular and biochemical effects of an insecticidal toxin extracted from Meloidae beetles were investigated on Helicoverpa armigera. The toxin was identified as cantharidin, a well-known natural compound produced by beetles of family Meloidae and Oedemeridae. Furthermore, the effect of the toxin on the metabolic enzymes alkaline phosphatase (ALP) and glutathione S-transferase (GST), responsible for the metabolism of insecticides, was also investigated. Results of a diet incorporation bioassay performed under laboratory conditions showed that the LC 50 value of cantharidin was 0.068 mg/g. The body weight of the insect was also significantly reduced by cantharidin treatment. The LC 10 concentration of cantharidin, 0.01 mg/g, was also tested to determine its effect on ALP and GST. Our results showed that cantharidin significantly inhibited ALP activity after 48 h, whereas GST activity was significantly inhibited after 24 h. The decline of ALP and GST transcript levels was also validated by semiquantitative RT-PCR analysis. It may be concluded from the results that ALPs and GSTs may be targets of the cantharidin intoxication mechanism. Moreover, the inability of ALP and GST to metabolize cantharidin shows that the mechanism of detoxification for cantharidin is different from that for conventional insecticides. On the basis of our investigations, the chemical structure of insecticides may be modified using a model structure of cantharidin, to avoid metabolism by metabolic enzymes.

Cantharimide and Its Derivatives from the Blister Beetle Mylabris phalerata Palla

“…2 Cantharidin is a wellknown natural compound produced only by beetles of the families Meloidae and Oedemeridae. 3 It has attracted the attention of synthetic chemists and pharmacologists due to its toxicity and antitumor activities especially in HepG2 (human hepatocellular carcinoma) cells, 4 human pancreatic cancer cells, 5 bladder cancer cells, 6 lung cancer cells, 7 and gastric cancer cells. 8 The related compounds the cantharimides represent a rare class of natural compounds in which the anhydride oxygen atom in cantharidin is replaced by a nitrogen that is either unsubstituted or substituted, and their pharmacological activities have not been reported.…”

“…They have been used for the treatment of rabies, dropsy, warts, impotence, and fever as traditional medicines for 2000 years in China . Cantharidin is a well-known natural compound produced only by beetles of the families Meloidae and Oedemeridae . It has attracted the attention of synthetic chemists and pharmacologists due to its toxicity and antitumor activities especially in HepG2 (human hepatocellular carcinoma) cells, human pancreatic cancer cells, bladder cancer cells, lung cancer cells, and gastric cancer cells .…”