Anticholinesterase Potential of Monoterpenoids on t he Whitefly Bemisia tabaci and Their Kinetic Studie

Abstract

B-biotype Bemisia tabaci is a severe insect pest worldwide in many ornament al, agricultural, and horticultural crops. Control of t his insect is obstructed by resistance to many AcetylCholinEsterase (AChE)-inhibiting insecti cides, such as organophosphates and carbamates. In the present work, we evaluated t he acetylcholinesterase inhibitory activity of six monoterpenoids namely α -pinene, terpineol, linalool, ß-myrcene, nerol and geraniol in vitro and in vivo . Inhibition of AChE of B. tabaci was measured by colorimetric method. The results showed that all of the monoterp enoids produced AChE inhibitory activity, with IC 50 values ranging from 0.96 to 26.85 mM. Alpha-pinene showed the most potent inhibitory activity (IC 50 = 0.96 mM). Kinetic analysis showed reversible non- competitive type inhibition, revealing that these c omponents might bind both the enzyme alone and the enzyme-substrate. Results demonstrate the AChE inhibitory activity as mode of action of these monoterpenoids at relativel y high concentrations. Thus, this could be useful for investigation of new ecofriendly natu ral insecticidal compounds. Keywords: Acetylcholinesterase, Bemisia tabaci , , IPM, Monoterpenoids, Non-competitive inhibition