Insecticidal properties of pyripyropene A, a microbial secondary metabolite, against agricultural pests

Afidopyropen, a novel insecticide originating from microbial secondary extracts

Afidopyropen, a novel insecticide, is a derivative of pyripyropene A, which is produced by the filamentous fungus Penicillium coprobium. Afidopyropen has strong insecticidal activity against aphids and is currently used as a control agent of sucking pests worldwide. In this study, we summarized the biological properties and field efficacies of its derivatives against agricultural pests using official field trials conducted in Japan. Afidopyropen showed good residual efficacies against a variety of aphids, whiteflies and other sucking pests under field conditions. Furthermore, toxicological studies revealed its safety profiles against nontarget organisms, such as the honeybee, natural enemies and other beneficial insects, as well as mammals. Thus, afidopyropen is a next-generation agrochemical for crop protection that has a low environmental impact.

Talaromyces-Insect Relationships

Facing the urgent need to reduce the input of agrochemicals, in recent years, the ecological relationships between plants and their associated microorganisms have been increasingly considered as an essential tool for improving crop production. New findings and data have been accumulated showing that the application of fungi can go beyond the specific role that has been traditionally assigned to the species, employed in integrated pest management as entomopathogens or mycoparasites, and that strains combining both aptitudes can be identified and possibly used as multipurpose biocontrol agents. Mainly considered for their antagonistic relationships with plant pathogenic fungi, species in the genus Talaromyces have been more and more widely reported as insect associates in investigations carried out in various agricultural and non-agricultural contexts. Out of a total of over 170 species currently accepted in this genus, so far, 27 have been found to have an association with insects from 9 orders, with an evident increasing trend. The nature of their mutualistic and antagonistic relationships with insects, and their ability to synthesize bioactive compounds possibly involved in the expression of the latter kind of interactions, are analyzed in this paper with reference to the ecological impact and applicative perspectives in crop protection.

Unlocking Nature's Biosynthetic Power-Metabolic Engineering for the Fermentative Production of Chemicals

Fermentation as a production method for chemicals is especially attractive, as it is based on cheap renewable raw materials and often exhibits advantages in terms of costs and sustainability. The tremendous development of technology in bioscience has resulted in an exponentially increasing knowledge about biological systems and has become the main driver for innovations in the field of metabolic engineering. Progress in recombinant DNA technology, genomics, and computational methods open new, cheaper, and faster ways to metabolically engineer microorganisms. Existing biosynthetic pathways for natural products, such as vitamins, organic acids, amino acids, or secondary metabolites, can be discovered and optimized efficiently, thereby enabling competitive commercial production processes. Novel biosynthetic routes can now be designed by the rearrangement of nature's unlimited number of enzymes and metabolic pathways in microbial strains. This expands the range of chemicals accessible by biotechnology and has yielded the first commercial products, while new fermentation technologies targeting novel active ingredients, commodity chemicals, and CO₂ -fixation methods are on the horizon.

Development of novel pesticides in the 21st century

General trends and strategies for novel pesticides are summarized. Global pesticide sales and pesticide discovery research are also briefly reviewed. At least 105 chemical pesticides have been launched during the past decade or are under development: 43 fungicides, 34 insecticides/acaricides, 6 nematicides, 21 herbicides, and 1 herbicide safener. Most of them are safe to humans and environmentally friendly. The most developed fungicides are SDHI (succinate dehydrogenase inhibitors), DMI (demethylation inhibitors), QoI (quinone outside inhibitors), and QiI (quinone inside inhibitors). Due to the development of resistance to fungicides with existing modes of action, many fungicides possessing various novel modes of action have been launched or are under development. The trend of insecticide development is changing from organophosphorus, carbamate, and synthetic pyrethroids to nicotinic and diamide insecticides. During the past decade, compounds possessing a variety of novel modes of action have also been launched or are under development. Flupyradifurone and flupyrimin, exhibiting extremely low honeybee toxicity, have been developed and subjected to practical use. Herbicides possessing varied modes of action, such as acetolactate synthase, p-hydroxyphenylpyruvate dioxygenase, protoporphyrinogen oxidase, and very-long-chain fatty acid elongase inhibition, have been developed, but no herbicides possessing a novel mode action have commercialized in nearly 30 years. It is of interest that cyclopyrimorate, which was recently launched, and tetflupyrolimet, which is under development, have novel modes action: homogentisate solanesyltransferase (HST) and dihydroorotate dehydrogenase (DHODH) inhibition, respectively. The development of useful acaricides and nematicides is also progressing. Some natural product origin pesticides are getting attention.

Synthesis of pyripyropene derivatives and their pest-control efficacy

Pyripyropene A (PP-A), a secondary metabolite produced by filamentous fungi, shows insecticidal activity against agricultural insect pests. Synthesized PP derivatives also show a narrow insecticidal spectrum but high insecticidal activities against such sucking pests. PP-A has a low eco-toxicological impact and satisfies a prerequisite for next-generation insecticides. We investigated the effects of conversion of the 3-pyridyl and α-pyrone rings to other rings, as well as the effects of esterification, dehydration, and oxidization at the C-13 position in natural PP analogues, on the insecticidal activity and spectrum. The conversions of the 3-pyridyl and α-pyrone rings markedly reduced the insecticidal activity with a minimal impact on the spectrum, indicative of an important role for these rings in insecticidal activity. Some derivatives with modified structures at the C-13 position showed a higher inhibitory effect on the motility of canine heartworms and mosquito vectors than did PP-A, suggesting their utility as filaria control drugs.

Synthesis and insecticidal efficacy of pyripyropene derivatives. Part II-Invention of afidopyropen

The synthesis and insecticidal activity of a series of pyripyropene derivatives with cyclopropanecarbonyloxy group(s) at the C-1, C-7 and/or C-11 position(s) were investigated to find novel insecticides. Insecticidal screening of the synthesized PP derivatives revealed that derivative 13, which had cyclopropanecarbonyloxy groups at the C-1 and C-11 positions and a hydroxyl group at the C-7 position, showed the highest insecticidal activity against aphids in laboratory tests. Finally, we selected 13 as a new insecticide candidate for agricultural sucking pests, which is now commercialized under the common name afidopyropen.