Fumigant and Contact Toxicities of Monoterpenes to Sitophilus oryzae (L.) and Tribolium castaneum (Herbst) and their Inhibitory Effects on Acetylcholinesterase Activity

Abstract

A comparative study was conducted to assess the contact and fumigant toxicities of eleven monoterpenes on two important stored products insects--, Sitophilus oryzae, the rice weevil, and Tribolium castaneum, the rust red flour beetle. The monoterpenes included: camphene, (+)-camphor, (-)-carvone, 1-8-cineole, cuminaldehyde, (L: )-fenchone, geraniol, (-)-limonene, (-)-linalool, (-)-menthol, and myrcene. The inhibitory effect of these compounds on acetylcholinesterase (AChE) activity also was examined to explore their possible mode(s) of toxic action. Although most of the compounds were toxic to S. oryzae and T. castaneum, their toxicity varied with insect species and with the bioassay test. In contact toxicity assays, (-)-carvone, geraniol, and cuminaldehyde showed the highest toxicity against S. oryzae with LC(50) values of 28.17, 28.76, and 42.08 microg/cm(2), respectively. (-)-Carvone (LC(50) = 19.80 microg/cm(2)) was the most effective compound against T. castaneum, followed by cuminaldehyde (LC(50) = 32.59 microg/cm(2)). In contrast, camphene, (+)-camphor, 1-8-cineole, and myrcene had weak activity against both insects (i.e., LC(50) values above 500 microg/cm(2)). In fumigant toxicity assays, 1-8-cineole was the most effective against S. oryzae and T. castaneum (LC(50) = 14.19 and 17.16 mg/l, respectively). Structure-toxicity investigations revealed that (-)-carvone--, a ketone--, had the highest contact toxicity against the both insects. 1-8-Cineole--, an ether--, was the most potent fumigant against both insects. In vitro inhibition studies of AChE from adults of S. oryzae showed that cuminaldehyde most effectively inhibited enzyme activity at the two tested concentrations (0.01 and 0.05 M) followed by 1-8-cineole, (-)-limonene, and (L)-fenchone. 1-8-Cineole was the most potent inhibitor of AChE activity from T. castaneum larvae followed by (-)-carvone and (-)-limonene. The results of the present study indicate that (-)-carvone, 1,8-cineole, cuminaldehyde, (L)-fenchone, and (-)-limonene could be effective biocontrol agents against S. oryzae and T. castaneum.

Cuminaldehyde: A Potential Drug Candidate

“…Cuminaldehyde was also found to selectively inhibit the acetylcholinesterase in insects and pests feeding on and damaging plants and therefore it could be safely used as an excellent natural bio-fumigant [30][31][32].…”

Phytochemical study and insecticidal activity of Mentha pulegium L. oils from Morocco against Sitophilus Oryzae

“…The effectiveness of the pennyroyal oil may be attributed to its chemical composition generally and particularly to monoterpenes that act as insecticidal agents 41 . Our plant is rich in monoterpenes (96.87%) mainly pulegone (68.86%) and piperitenone (24.81%), thymol (1.01%), limonene (0.9%) and pinene (0.32%).…”

“…Our plant is rich in monoterpenes (96.87%) mainly pulegone (68.86%) and piperitenone (24.81%), thymol (1.01%), limonene (0.9%) and pinene (0.32%). These active components have shown an important insecticidal activity against several pests 14,21,30,[41][42][43] .…”

“…The toxic effect of M. pulegium essential oils against S. oryzae may be attributed to the inhibition of neurotransmitters such as acetylcholinesterase 41,48 and octopamine 49 .…”

Essential oils and their components as an alternative in the control of mosquito vectors of disease

“…Se ha informado que los aldehídos aislados no son importantes para el efecto larvicida; sin embargo, cuando el aldehído está conjugado con un sistema aromático, esto contribuye positivamente a su actividad (124). Este efecto se observa en la gran potencia larvicida del cinamaldehído, un fenilpropanoide totalmente conjugado (103).…”