Structure/activity relationship of some natural monoterpenes as acaricides against Psoroptes cuniculi.

The pharmacological activity of many essential oils on a large number of human and animal pathogens, as used in folk medicine, has been confirmed world-wide by several laboratory investigations. Unfortunately, the biological properties of essential oils can be extremely inconsistent because of the variability of their chemical composition. The acaricidal activities of some natural terpenoids, which are the main constitutents of several essential oils, were evaluated in vitro against the mange mite (Psoroptes cuniculi) of the rabbit, by direct contact and by inhalation. Because the test components represent different chemical classes (hydrocarbons, alcohols, and phenols, with free and esterified or etherified functional groups), it was also possible to discern in a preliminary fashion a correlation between chemical structure and acaricidal activity. The results obtained suggest that molecules possessing free alcoholic or phenolic groups showed the most potent acaricidal activity.