Botanical Pesticides: Current Challenges and Reverse Pharmacological Approach for Future Discoveries

In ancient culture and in different parts of world, there exist empirical knowledge of the use of plants for pest control for thousands of years (approx. 1500 BC), for example rotenone in east Asia and south America, neem in India, sabadilla in central and south America, and pyrethrin in Persia (Iran). Subsequently, botanical insecticides were introduced in prominent continents like Europe and United states [1]. Botanicals (phytochemicals) are basically secondary metabolites that serve as means of defense mechanism of the plants to withstand the continuous selection pressure from herbivore predators and other environmental factors. Many groups of phytochemicals such as steroids, alkaloids, terpenoids, phenolics and essential oils from more than 2000 plant species have been reported previously for their insecticidal activities. Applications of phytochemicals in mosquito control were in use since 1920, but the discovery of synthetic insecticides such as DDT in 1939 sidetracked the application of phytochemicals in different segments. Synthetic insecticides spread easily and rapidly because it won space on market as products being effective, cheaper, long lasting and easily available. After facing problems due to injudicious and over application of synthetic insecticides in nature, refocus on phytochemicals that are easily biodegradable and have no ill effects on non-target organisms was appreciated. From 1990s, there is renewed interest for use of botanical pesticides due to concerns raised about the rampant supply of synthetic insecticides and its irreversible impact on health and environment; its presence in food web is quite worrying matter for health professionals. At present, phytochemicals make up to 1% of world’s pesticide market [2].