Recent progress of highly efficient in vivo biological screening for novel agrochemicals in China

Modern Approaches for the Development of New Herbicides Based on Natural Compounds

Weeds are a permanent component of anthropogenic ecosystems. They require strict control to avoid the accumulation of their long-lasting seeds in the soil. With high crop infestation, many elements of crop production technologies (fertilization, productive varieties, growth stimulators, etc.) turn out to be practically meaningless due to high yield losses. Intensive use of chemical herbicides (CHs) has led to undesirable consequences: contamination of soil and wastewater, accumulation of their residues in the crop, and the emergence of CH-resistant populations of weeds. In this regard, the development of environmentally friendly CHs with new mechanisms of action is relevant. The natural phytotoxins of plant or microbial origin may be explored directly in herbicidal formulations (biorational CHs) or indirectly as scaffolds for nature-derived CHs. This review considers (1) the main current trends in the development of CHs that may be important for the enhancement of biorational herbicides; (2) the advances in the development and practical application of natural compounds for weed control; (3) the use of phytotoxins as prototypes of synthetic herbicides. Some modern approaches, such as computational methods of virtual screening and design of herbicidal molecules, development of modern formulations, and determination of molecular targets, are stressed as crucial to make the exploration of natural compounds more effective.

The Chemical Ecology Approach to Reveal Fungal Metabolites for Arthropod Pest Management

Biorational insecticides (for instance, avermectins, spinosins, azadirachtin, and afidopyropen) of natural origin are increasingly being used in agriculture. The review considers the chemical ecology approach for the search for new compounds with insecticidal properties (entomotoxic, antifeedant, and hormonal) produced by fungi of various ecological groups (entomopathogens, soil saprotrophs, endophytes, phytopathogens, and mushrooms). The literature survey revealed that insecticidal metabolites of entomopathogenic fungi have not been sufficiently studied, and most of the well-characterized compounds show moderate insecticidal activity. The greatest number of substances with insecticidal properties was found to be produced by soil fungi, mainly from the genera Aspergillus and Penicillium. Metabolites with insecticidal and antifeedant properties were also found in endophytic and phytopathogenic fungi. It was noted that insect pests of stored products are mostly low sensitive to mycotoxins. Mushrooms were found to be promising producers of antifeedant compounds as well as insecticidal proteins. The expansion of the number of substances with insecticidal properties detected in prospective fungal species is possible by mining fungal genomes for secondary metabolite gene clusters and secreted proteins with their subsequent activation by various methods. The efficacy of these studies can be increased with high-throughput techniques of extraction of fungal metabolites and their analysis by various methods of chromatography and mass spectrometry.

Synthesis of 2-amino-6-oxocyclohexenylsulfonamides and their activity against Botrytis cinerea

BACKGROUND

With the objective of exploring the fungicidal activity of 2-oxocyclohexylsulfonamides (2), a series of novel 2-amino-6-oxocyclohexenylsulfonamides (6 to 23) were synthesised, and their fungicidal activities against Botrytis cinerea Pers. were evaluated in vitro and in vivo.

RESULTS

The compounds were characterised by IR, 1H NMR and elemental analysis. Bioassay results of mycelial growth showed that compounds 6 to 23 had a moderate antifungal activity against B. cinerea. N-(2-methylphenyl)-2-(2-methylphenylamino)-4,4-dimethyl-6-oxocyclohexenylsulfonamide (13) and N-(2-chlorophenyl)-2-(2-chlorophenylamino)-6-oxocyclohexenylsulfonamide (21) showed best antifungal activities, with EC50 values of 8.05 and 10.56 µg mL(-1) respectively. Commercial fungicide procymidone provided an EC50 value of 0.63 µg mL(-1) . The conidial germination assay showed that most of compounds 6 to 23 possessed excellent inhibition of spore germination and germ-tube elongation of conidia of B. cinerea. For in vivo control of B. cinerea colonising cucumber leaves, the compound N-cyclohexyl-2-(cyclohexylamino)-4,4-dimethyl-6-oxocyclohexenylsulfonamide (19) showed a better control effect than the commercial fungicide procymidone.

CONCLUSION

The present work demonstrated that 2-amino-6-oxocyclohexenylsulfonamides can be used as possible new lead compounds for further developing novel fungicides against B. cinerea.

China: forward to the green pesticides via a basic research program

The 973 Program is China's keystone national research program established to support basic research in natural and physical sciences. In addition to promoting the development of core technology and scientific infrastructure needed to enable China to meet the social and economic challenges of the 21st century, the training and mentoring of the new generation of China's young scientists are also important objectives of this national program. The green chemical pesticide research program is a part of the 973 Program. The main objectives of stage 1 of the green chemical pesticide research program (2003-2008) are to establish China's capability to conduct basic research in the discovery of "green" crop protection chemicals that are not only novel in mode of action and highly selective to pest species that are unique to China's agricultural situation but also possess favorable environmental and human hazard and risk potentials. The target-based discovery strategy was selected as the main discovery platform. This strategy not only provided this research program the best chance to discover new products but also provided members of this research team opportunities to establish core technologies in chemoinformatics/computation-aided pesticide design using QSAR, QAAR, sensitive and selective bioassay methodology, combinatorial synthesis, hit to lead optimization, and biological targets that were derived from resistance-AChE, IGR, nAChR, etc. On the basis of the learning from stage 1, stage 2 (2010-2014) of this program will focus on the molecular target-oriented innovation of green chemical pesticides. This commentary presents key learnings and accomplishments from the stage 1 of China's green chemical pesticide research program. It is hoped that this information will stimulate further constructive collaborations between pesticide scientists from China and abroad.