The two-spotted spider mite, Tetranychus urticae Koch, has a broad host plant range and presents an extreme capacity for developing pesticide resistance, becoming a major economic pest in agriculture. Anticholinesterase insecticides still account for a big part of global insecticide sales. However, there is a growing concern about the serious resistance problems of anticholinesterase insecticides and their nontarget toxicity. In this study, structure-based virtual screening was performed to discover selective AChE inhibitors from the ChemBridge database, and 39 potential species-specific AChE inhibitor were obtained targeting T. urticae AChE, but not human AChE. Among them, compound No. 8 inhibited AChE from T. urticae, but not from human, and had an inhibitory activity comparable to that of eserine. Compound No. 8 had dose-dependent toxicity to T. urticae in glass slide-dipping assay and had significant mite control effects in a pot experiment, but required a high concentration to achieve similar control effects to spirodiclofen. The toxicity evaluation suggested that compound No. 8 had no acute toxicity on pollinator honey bees and natural predator N. californicus and did not affect strawberry growth in our assay. Compound No. 8 is a potential lead compound for developing novel acaricides with reduced nontarget toxicity.

The carmine spider mite, Tetranychus cinnabarinus (Acari: Tetranychidae), is an economically important and extremely polyphagous herbivorous pest, with the title of \"resistance champion\" among arthropods. Anticholinesterase insecticides such as organophosphate and carbamate account for more than one-third of global insecticide sales. The non-target toxicity and resistance problem of organophosphate and carbamate have become of growing concern, which may be due to the fact that they target the ubiquitous catalytic serine residue of acetylcholinesterase (AChE) in mammals, birds, and beneficial insects. In this study, the structural differences between T. cinnabarinus AChE and human AChE, at or near the catalytic pocket, were illustrated. From the SPECS chemical lead-compound database, 55 AChE inhibitor candidates were screened for high affinity for T. cinnabarinus AChE, but low affinity for human AChE, using the DOCK 6 and AutoDock Vina software. Three of the fifty-five candidates had inhibitory activity greater than that of the reversible AChE inhibitor eserine, with no observed inhibitory activities against human AChE. Two of the three had toxicity to T. cinnabarinus comparable to that of natural insecticidal pyrethrins. However, their potency is low compared with that of etoxazole, and further work is needed to optimize their potency. The selectivity of the three compounds over human and mite AChE may be due to their interaction with the mite-specific residues, as analyzed by Cyscore. The three compounds are potential lead compounds for development of novel acaricides against T. cinnabarinus with reduced toxicity to non-target species and a low propensity for resistance.

The anticholinesterase and antioxidant effects of five different extracts of Piper nigrum were evaluated. Twenty-one known alkamides were isolated from active ethyl acetate extract and investigated for their cholinesterase inhibitory and antioxidant effects. Among them, piperine (2), piperettine (5) and piperettyline (20) exhibited dual inhibition against AChE and BChE, and feruperine (18) was the most potent selective inhibitor of BChE. Molecular docking simulation was performed to get insight into the binding interactions of the ligands and enzymes. In addition, N-trans-feruloyltyramine (3) contributed to the strongest DPPH radical-scavenging activity. The self-induced Aβ aggregation inhibition of 2, 5 and 18 was further evaluated. Results indicated that some alkamides could be multifunctional lead candidates for Alzheimer\'s disease therapy.