Plant extracts in prevention of mosquito attacks.

Abstract

Listen

Translate article

Abstract Plants and plant-derived substances have been used to repel or kill mosquitoes and other domestic pest insects for a long time before the advent of synthetic chemicals. Essential oils of a large number of plants have repellent action and many have formed the basis of commercial repellent formulations. These insecticidal phytochemicals include glycosides, alkaloids, saponins, tannins, essential oils, mustard oils, cyanogens, phenolics, amino acid analogues, nonprotein amino acids, proteinase inhibitors, cardiac glycosides and other organic compounds. Terpenoids are the most widespread and structurally diverse of the plant products. Volatile chemical substances acting in the vapour phase have been used for a long time as repellents to prevent insects landing and biting. They are used to protect humans and animals from insects by making the hosts objectionable or unattractive. Most commercially available 'natural' insect repellents in Asia, Europe and the USA are based on essential oils. An important natural compound extracted from lemon eucalyptus, Eucalyptus maculata citriodon, is p-menthane-3,8-diol (PMD) which has a pleasant lemon-like odour. Repellency evaluation is preferably carried out using human subjects, as testing repellents on animals or artificial membranes may not give representative data of how the repellent will perform when applied to human skin. Field trials should be carried out, particularly to evaluate the operational feasibility and acceptability on the skin over a long period, especially by infants and children. It is important to determine whether widespread use of one of these repellents would produce an overall reduction of vector biting in a community or would simply divert biting from repellent users to non-users.