Potential of Azadirachtin and Neem (Azadirachta indica) Based Saponins as Biopesticides for In vitro Insect Pests Cellulase (Beta-1,4-Endoglucanase) Enzyme Inhibition and In vivo Repellency on Tribolium castaneum

Aims: The work was undertaken to identify the role of Neem derived compounds (saponins and azadirachtin) on the digestive cellulose hydrolyzing enzyme activity of red flour beetle (T. castaneum), rice grasshopper (Oxya chinensis) and red pumpkin beetle (Aulacophora foveicolis).

Place and Duration of Study: The work was carried out at the Institute of Biochemistry and Biotechnology University of the Punjab Lahore Pakistan.

Methodology: Total cellular proteins were isolated from the insect’s gut and salivary glands and were tested for cellulose hydrolyzing activity on substrate agar plates. Saponins and Azadirachtin were isolated from Azadirachta indica tissues and used for enzyme inhibition studies. Repellancy test was performed for T. Castaneum, using saponins and Azadirachtin. For computational studies sequence of endoglucanase gene was identified from T. castaneum genome and protein structure was deduced.

Results: Saponins were able to inhibit beta-1,4-endoglucanase enzyme activity, present in all the three insect pests. A computational dissection of T. castaneum endoglucanase enzyme, deduced from T. castaneum genome, showed that there were five cys involved in the formation of disulphide bridges in the molecule. The disulfide bridges did not provide any protection to endoglucanase active site. Azadirachtin had no effect on cellulase activity of Oxya chinensis and Aulacophora foveicolis, while beta-1,4-endoglucanase activity of T. castaneum was inhibited. Repellency test for T. castaneum revealed that each group of compounds (Saponins and Azadirachtin) was able to repel the insect.

Conclusion: Neem derived compounds had a considerable inhibitory effect on the digestive cellulose hydrolyzing enzyme of T. castaneum.