Location: Natural Products Utilization Research
2020 Annual Report
Objectives
1. Develop biopesticides to improve control of arthropods.
1.1. Discover novel bioinsecticide active ingredients from crude plant extract screening and bioassay-directed fractionation.
1.2. Discovery of fungal compounds with activity against permethrin-resistant and susceptible mosquitoes.
2. Develop biorepellents to improve control of arthropods.
2.1. Discover novel arthropod repelling biopesticides from mosquito repelling folk remedies and plant essential oils.
2.2. Development and optimization of the chromene derivative 131-1 as a biopesticide.
3. Develop natural product synthetic analogs for management and control of arthropods.
3.1. Use synthetic methods to develop and optimize fatty acids as natural topical and spatial arthropod repellents.
3.2. 131-1 Development into a commercial mosquito repelling product.
Approach
A bioassay-directed investigative approach will be performed on bioactive extracts in efforts to discover bioinsecticides and repellents for use against arthropod pests. General procedures for isolation of active compounds from plants and microbes will be utilized. Solvent extractions, liquid-liquid partitioning, column chromatography and thin layer chromatography will be employed as needed. Extracts, fractions and pure compounds will be tested for insecticidal and insect repellent activity in assays being carried out routinely at collaborator's laboratories. Identification of active compounds will be done using spectroscopic methods including mass spectroscopy (EI, CI, and high resolution ESI), nuclear magnetic resonance (one- and two-dimensional). Chemical modification will be performed on compound(s) identified as "highly active" to improve activity or bioavailability.
Progress Report
Actinomycetes, especially Streptomyces species are widely recognized as industrially important microorganisms that are studied of bio-pesticides, including fungi, actinomycetes, bacteria, viruses, and nematodes, have been reported as potent materials for biological control. The present study has been undertaken to isolate, characterize, and evaluate the larvicidal (Aedes aegypti) compounds produced by Streptomyces distallicus. For developing the fermentation methodology, we tested and optimized several different fermentation conditions for S. distallicus through High Performance Liquid Chromatography (HPLC) analysis and in-vitro assay. While successfully developing the fermentation methodology, novel bioactive products were discovered and isolated. The most active compound was determined to be an aureothin analog. This is the first report on exploring novel products from Streptomyces distallicus for developing microbial bioinsecticides to be used in the management of Aedes mosquito larvae. Building from the discovery above, we conducted a study to assess the potential of Streptomyces orinoci as a source of new microbial bioinsecticides. For developing the fermentation methodology, we tested and optimized several different fermentation conditions for S. orinoci through HPLC analysis and in-vitro assays. While successfully developing the fermentation methodology, three crude extractions showed potent larvicidal activities. Further studies toward the identification of specific bioactive compounds and their detailed biochemical pathways and physiological studies are currently underway. This is the first study to explore novel products from Streptomyces orinoci for developing microbial bioinsecticides to be used in the management of Aedes mosquito larvae.
Stureja pilosa Velen. is a Balkan endemic plant that is not well characterized and is found on rocky outcrops of limestone base in Stara Planina (the Balkan Mountains) and the Rhodope Mountains. In collaboration with colleagues at the University of Mississippi, this study was initially implemented to assess the variability of essential oil (EO) content and composition of S. pilosa collected at 33 locations across the Balkan and Rhodope Mountains in Bulgaria. Biological evaluation of the essential oil revealed five different chemotypes which exhibited larvicidal and mosquito repellent activity against Ae. aegypti. Additional plant extracts have been evaluated for repellent activity against Ae. aegypti and investigations are underway to isolate the bioactive constituents.
Esters of C-11:0 and C-12:0 fatty acids were synthesized last fiscal year in an effort to both improve the mosquito repellency and improve the duration of activity of the natural C-11 and C-12 fatty acids. The optimum chain length for the esters has been determined and a highly active analog has been produced and shown to be more active than DEET in the Klun & Debboun (K&D) module bioassay system. Additional evaluations were performed in the Ali & Khan (A&K) bioassays this year. In-vivo evaluations of the most active compounds against Ae. aegypti were performed following the large scale synthesis of the analogs. In the A&K assay, undecanoic acid appears to be the most active compound in this group tested while butyl undecanoate was the most active ester analog synthesized. Both of these highly effective compounds are more effective than DEET and warrant further investigations as mosquito repellents. In collaboration with a CRADA partner, the mosquito repellent 131-1 has been produced in large quantities. This is the first synthetic batch produced outside of the unit in an attempt to transfer the technology to the private sector. The product produced is being evaluated for Ae. aegypti repellency by collaborators at the Center for Medical, Agricultural, and Veterinary Entomology (CMAVE) in Gainesville, Florida.
Accomplishments
Review Publications
Semerdjieva, I.B., Zheljazkov, V.D., Cantrell, C.L., Astatkie, T., Ali, A. 2020. Essential oil yield and composition of the Balkan endemic Satureja pilosa Velen. (Lamiaceae). Molecules. 25(4):827. https://doi.org/10.3390/molecules25040827.
Liu, X., Yu, W., Min, L., Wedge, D., Tan, C., Weng, J., Wu, H., Cantrell, C.L., Bajsa Hirschel, J.N., Hua, X., Duke, S.O. 2020. Synthesis and pesticidal activities of new Quinoxalines. Journal of Agricultural and Food Chemistry. 68:7324-7332. https://doi.org/10.1021/acs.jafc.0c01042.
Cantrell, C.L., Zaki, M., Reichley, A.C., Kim, S.J. Sink, M.C., Ali, A. 2020. Biting deterrency of Undecanoic acid and Dodecanoic acid ester analogs against Aedes aegypti. Pest Management Science. https://doi.org/10.1002/ps.5994.
