Infected mosquitoes from the genus Aedes have become one of the most influential contributors to human morbidity and death globally. To explore novel biopesticides with activity against Aedes aegypti, the species Streptomyces distallicus, related to the subspecies of Streptomyces netropsis was studied. Six metabolites, aureothin, allo-aureothin, deoxyaureothin, 4',7-dihydroxy isoflavone, 2-methyl-5-(3-indolyl)oxazole, and 2-ethyl-5-(3-indolyl)oxazole, have been isolated, and the metabolites were analyzed and elucidated by one-dimensional and two-dimensional NMR, spectroscopic analysis, and HRMS. The isolated compounds were evaluated for their larvicidal activity against Aedes aegypti. Only aureothin and allo-aureothin showed larvicidal activity against A. aegypti activities with LC50 values of 1.5 ppm and 3.1 ppm for 24 h post-treatment, respectively, and 3.8 ppm and 7.4 ppm for 48 h post-treatment, respectively. Aureothin was also evaluated for activity against the red imported fire ant, Solenopsis invicta (mean average mortality rate = 7.16% and 9.44% in 24 h and 48 h post-treatment, respectively, at the dose of 9.6 μg/ant). Streptomyces distallicus is a promising source of a potential microbial larvicide, and the synergistic larval-killing effect of metabolites from S. distallicus deserves further investigation.

Streptomyces distallicus, a potential microbial biolarvicide

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