Investigation of Biopesticides for the Pest Control Through Inhibition of the Acetylcholinesterase Purified from Loxostege sticticalis (L.) (Lepidoptera: Crambidae).

Acetylcholinesterase (AChE) is a cholinergic enzyme called acetylcholine acetylhydrolase. Acetylcholinesterase inhibition is one of the prominent methods in studies on pest control management. In this study, AChE was purified 103.7-fold from Loxostege sticticalis (L.) using an Edrophonium-Sepharose 6B affinity column, and some kinetic properties were investigated. The molecular weight of the purified enzyme was determined by Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE). Inhibition studies of AChE were realized with tacrine, edrophonium chloride, and cypermethrin, which are known inhibitors of AChE, as well as aqueous extracts of certain plant leaves. The subunit molecular weight of purified AChE was estimated to be approximately 56 kDa by SDS-PAGE analysis. The maximum activity of Loxostege sticticalis AChE was specified at 40.0 °C and pH 8.0. V, K and k values of the AChE were determined as 243.9 ± 15.7 EU/mg protein, 0.122 ± 0.06 mM, and 13.7 ± 2.7 min, respectively. In the inhibition studies, the IC values of tacrine, edrophonium chloride and cypermethrin were found to be 3.4 ± 0.5, 0.08 ± 0.006 and 85.0 ± 4.1 μM, respectively. Besides, the IC values of aqueous extracts of olive leaf, alder leaf, walnut leaf, cherry laurel leaf, and plane leaf were as 12.0 ± 0.6, 15.2± 1.3, 32.1 ± 1.5, 58.3 ± 1.9, and 75.2 ± 2.8 µg dry matter/mL, respectively. In addition, the oleuropein and phenolic substance amounts of these plant extracts were determined and correlated with the IC values. Consequently, the plant extracts used in this study may be recommended as an alternative biopesticide source to control such pests via AChE inhibition.