Quantitative Calculation Of The Repellency Influence From The Association Between Terpenoid Repellents And Attractants

As a kind of main sanitary insect pests, mosquitoes transmit many kinds of fatal epidemic diseases worldwide, such as malaria, dengue fever, China epidemic encephalitis B, which greatly threaten to the health of human being. Therefore, mosquitoes control is an important tasks of integrated pest management all the time. Mosquito repellent not only have a potentcapability to repel mosquito, but also of great convenience and safety. However, the mechanism of repellent still unclear. It is believed that molecular interaction between repellent and attractant show an important influence to repellency, but relative researches have rarely been reported.Molecular interactions between terpenoid mosquito repellents and five typical attractants, L-lactic acid, ammonia,1-octen-3-ol, formic acid and carbonic acid were studied, and the effect of molecular interactions on repellency had benn estimated. The purpose of this research is to find a new theory for repelling mechanism. Following are the processes and results of this research.The intensity and type of molecular interaction between repellent and attractants were studied by theoretical calculation. Structures building and optimization were carried out by using GaussView 4.1, Gaussian 03 W package and AMPAC. Energy difference, distance, and angle of the molecular interaction were obtained thereby. The results showed that molecular interactions of moderate intensity between terpenoid mosquito repellents and five attractants did exist, stable complexes formed by hydrogen bond between repellent and attractant. Because of the presence of the adjacent carbonyl moiety, L-lactic acid-repellent, formic acid-repellent and carbonic acid-repellent interaction are stronger than 1-octen-3-ol-repellent and ammonia-repellent interaction. MoreH-bond donor in L-lactic acid, ammonia and carbonic acid result in more interaction types than l-octen-3-ol and formic acid.Influence from molecular interaction between repellent and attractant to repellency were discussed by quantitative structure-activity relationship method(QSAR). Descriptors of repellents, fragments, and complexes (formed by repellents and attractants) were calculated by AMPAC 8.16 and CODESSA 2.7.10 software. Heuristic method encoded in CODESSA 2.7.10 software was employed to screen significant descriptors for multilinear QSAR models building, which show the relationship between the structural descriptors and the logarithm value of the corrected repelling time against Aedes albopictus. The stability of these models were validated by leave-one-out validation and 3-fold internal validation. The result showed that five satisfying QSAR were obtained, three models comprise three descriptors, two models comprise four descriptors, respectively. R2 of any models are above 0.9. model validation indicated great stability to these models. Descriptors analysis suggested that each models comprise at least one descriptor from complexes or fragments, namely, descriptors from complexes or fragments significant correlated to the repellency.The connotation of these descriptors from complexes or fragments argue that the shape, conformation, spin properties of complexes and electrostatic energy of interaction area significantly affact the repellency.As a conclusion, hydrogen-bond interaction of certain intensity between terpenoid mosquito repellents and five typical human-secreted attractants, L-lactic acid, ammonia, 1-octen-3-ol, formic acid and carbonic acid did exist, which show an significant influence to the repelleny.