Natural Products-based Pesticide Discovery
The success of modern agricultural practices is due inpart to discovery and adoption of synthetic pesticide to control agricultural diseases in major agriculture crops. Although modern pesticides have reached aconsiderable level of efficacy associated with increasingly reduced toxicity, broad pesticidal spectrum and low use-rate, some environmental problems remain, as many of these pesticides are persistent enough to be detected after several weeks in crops and soil which give result in soil contamination or harmful effects to non target species, including humans. Numerous possible chronic effects concerning the exposing to residual pesticides present in food and water have been elucidated, including neurotoxicity, carcinogenesis,and reproduction influence et al. Moreover, the repeated applications of the pesticides over the years have resulted in the emergence of resistance in the insecticide population as well as in herbicidal and fungicidal population. Hence development of new effective, non persistent and safe pesticides, especially those with novel reaction mechanism or with the mode of action that different from the existing ones, is still a challenging task.
Natural products have been recognized as a key source for lead discovery in medicine chemistry as well as in argochemistry in recent yeas. Though only a few natural products are directly used as active ingredient in modern crop protection, it has inspiring agrochemical to develop novel lead structure. In fact, as of 2004,approximately 11% of global sales of agricultural pesticides are either natural product or compounds discovered as a result of chemical studies and structural modifications of active substance isolated or purified from plant or microbial.Thus following natural product leads offers an efficient approach to discovering and optimizing new agrochemical for plant disease control. Utilizing natural products for the discovery of new pesticides offers a number of advantages. For example, natural products generally have a high structural diversity compared with the synthetic pharmacophores .This make them possible to explore traditionally uncharted chemical spaces incomparison with synthetic molecules, and more likely to interact with new target sites, which afford an opportunity to the discovery of novel agrochemicals that operate by modes of action different from those of existing pesticides and, consequently, lack of cross-resistance to chemicals currently used.
The second very important benefit of natural product-based pesticides is that most of these compound share relatively short environmental half-lives, they usually degraded rapidly,which may due to the fact that they do not possess “unnatural” ring structures.Thus these compounds are perceived to be environmentally benign. However,natural products have their own limitation, the structural complexity of many natural products may be one of the drawbacks of these chemicals, the trace amount in the nature source lead to the difficulty for agricultural use in large scale, and the costs associated with their synthesis may be too expensive or even impossible for synthesis due to their complicated structures. At the same time, the rapidly degradation of natural products may be less than ideal for uptake into and translocation in plants to produce an adequate effect.Hence, the adjustment of the structure scaffold together with their physicochemical properties of natural products to meet the requirement of novel green agrochemicals is the permanent topic of modern natural product-based pesticide discovery.
Our natural product-based pesticide discovery project mainly focus on those natural products which have been elucidated possessing certain agrochemical properties including insecticidal activity, herbicidal activity or antibacterial properties, however, they can not be used as pesticides directly due to low biological potency or not suitable physicochemical properties. As the starting of our investigation, we would like to simplify the structure of the natural product and improve their activity as well by using total synthesis or designing novel synthetic methodology. The prepared natural product-based analogue library will be screened for assaying their biological potency and the molecule with high potency will be selected as lead for further structure optimization. During this process, the structure-activity relationship will be established and their physicochemical properties will also be evaluated. Finally, the mechanism of action will be taken into account to insight into their macromolecular target or their exact target site by combination the small organic molecular probe and chemical biology methodology.