Streptomyces distallicus, a potential microbial biolarvicide

Authors: Kim, Seong; Cantrell, Charles; AVULA, BHARATHI - University Of Mississippi; Chen, Jian; Schrader, Kevin; SANTO, SUIKINAI NOBRE - Biodiversity Microbial Technology; ALI, ABBAS - University Of Mississippi; KHAN, IKHLAS - University Of Mississippi

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2022
Publication Date: 8/30/2022
Citation: Kim, S., Cantrell, C.L., Avula, B., Chen, J., Schrader, K., Santo, S., Ali, A., Khan, I.A. 2022. Streptomyces distallicus, a potential microbial biolarvicide. Journal of Agricultural and Food Chemistry. https://pubs.acs.org/doi/10.1021/acs.jafc.2c03537.
DOI: https://doi.org/10.1021/acs.jafc.2c03537

Interpretive Summary: Mosquitoes are widely prevalent species of vectors capable of spreading diseases such as malaria, dengue fever, filariasis, yellow fever, etc. Mosquitos also affect humans by causing localized angioedema as well as skin and systemic allergic reactions. A relatively new threat, the Zika virus, is transmitted to humans via an infected mosquito from the genus Aedes, such as Ae. aegypti or Ae. albopictus. Consequently, infected mosquitos from the genus Aedes have become one of the world's most influential contributors to human morbidity and death. Microbial insecticides are currently a principal portion of the biopesticide industry. To explore new biopesticides with activity against Ae. aegypti, Streptomyces distallicus was investigated. The present study evaluated S. distallicus for the discovery of larvicidal compounds against Ae. aegypti for the first time. Herein, we describe the isolation and characterization of six compounds from S. distallicus, as well as their larvicidal activity against Ae. aegypti.

Technical Abstract: Infected mosquitos from the genus Aedes have become one of the world's most influential contributors to human morbidity and death. To explore new biopesticides with activity against Aedes aegypti, Streptomyces distallicus, a species related to the subspecies group of Streptomyces netropsis, was investigated. The six metabolites, aureothin, allo-aureothin, deoxyaureothin, 4',7- dihydroxy isoflavone, 2-methyl-5-(3-indolyl)oxazole, and 2-ethyl-5-(3-indolyl)oxazole, were isolated, and chemical structures were elucidated based on one- and two-dimensional NMR spectroscopy analyses and HRMS. The Aedes aegypti larvicidal activity of these compounds was evaluated. Only two isomeric compounds, aureothin and allo-aureothin, showed larvicidal activity against Ae. aegypti with LC50 values of 1.5 and 3.1 ppm for 24 h post-treatment, respectively, and 3.8 and 7.4 ppm for 48 h post-treatment, respectively. The crude extract of Streptomyces distallicus also demonstracted potent larvicidal activity with LC50 values of 1.46 and 1.2 ppm for 24 and 48 h post-treatment, respectively. Deoxyaureothin, a furan ring reduced form of aureothin, showed no activity against Ae. aegypti. The hybrid imported fire ants activity of aureothin was also evaluated, but it did not show any activity at the highest dose of 62.5 µg/g. Described here is the first report on a bioassay-directed investigation of the secondary metabolites of S. distallicus and biological evaluation of isolated compounds aureothin and its isomer and intermediates as potential microbial larvicides. S. distallicus and crude extracts thereof are a promising source of potential microbial biolarvicides.