Bio-efficacy of Soil Actinomycetes and an Isolated Molecule 1,2-Benzenedicarboxylic Acid from Nonomuraea sp. Against Culex quinquefasciatus Say and Aedes aegypti L. Mosquitoes (Diptera: Culicidae).

Vector-borne diseases such as filariasis and dengue that contribute significantly to disease burden, death, poverty, and social frailty are still a major public healthcare problem worldwide. Currently, synthetic chemicals have been used in mosquito control programs. However, repeated use of chemical insecticides causes environmental pollution and harmful effects on non-target organisms. Therefore, alternative ecofriendly sources from biological source are urgently needed to manage mosquitoes. In this respect, the present study was aimed to evaluate mosquito larvicidal and pupicidal activities of 22 crude extracts of soil actinomycetes on Culex quinquefasciatus and Aedes aegypti and to identify the active molecule. Briefly, the crude ethyl acetate extract and fractions were tested at 62.5, 125, 250, and 500 ppm and 2.5, 5.0, 7.5, and 10.0 ppm concentrations on larval and pupal stages of Cx. quinquefasciatus and Ae. aegypti. The larval and pupal mortality was assessed after 24 h of treatment. Among the 22 isolates screened, Nonomuraea sp. VAS-16 exhibited significant larvicidal and pupicidal activities against the tested mosquito species. Among the 18 fractions screened, fraction-6 showed strong larvicidal and pupicidal activities with the LC50 and LC90 values of 9.1, 18.7, 9.82, and 22.85 ppm against the larvae and LC50 and LC90 values of 10.5, 23.1, 12.3, and 24.13 ppm against the pupae of Cx. quinquefasciatus and Ae. aegypti, respectively. Fascinatingly, the isolated compound 1,2-benzenedicarboxylic acid from fraction-6 at 0.5, 1.0, 1.5, and 2.0 ppm concentration recorded lower LC50 and LC90 values of 4.27, 14.90, 4.67, and 11.90 ppm against the larvae and LC50 and LC90 values of 4.58, 12.06, 5.36, and 13.07 ppm against the pupae of Cx. quinquefasciatus and Ae. aegypti, respectively. On the other hand, the compound recorded less ovicidal activity of 11.0% and 10.3% at 2 ppm against the eggs of Cx. quinquefasciatus and Ae. aegypti, respectively. The present study clearly shows that the crude extract and the compound from Nonomuraea sp. VAS-16 can be used as an effective biopesticide in integrated mosquito management program.

In vitro antimicrobial, antioxidant and cytotoxic properties of Streptomyces lavendulae strain SCA5.

BACKGROUND: Actinomycetes are Gram-positive, often filamentous, bacteria known for their unsurpassed capacity for the production of secondary metabolites with diverse biological activities. The aim of the present study was to evaluate the antimicrobial, cytotoxic and antioxidant properties of Streptomyces lavendulae strain SCA5. RESULTS: The ethyl acetate extract of SCA5 broth (EA-SCA5) showed antimicrobial activity with MIC value of 31.25 µg/ml. EA-SCA5 showed good antioxidant potential by scavenging 2, 2-diphenyl-picrylhydrazyl (DPPH) (IC50 507.61 ± 0.66 µg/ml), hydroxyl radical (IC50 617.84 ± 0.57 µg/ml), nitric oxide (IC50 730.92 ± 0.81 µg/ml) and superoxide anion radical (IC50 864.71 ± 1.15 µg/ml). The EA-SCA5 also showed strong suppressive effect on rat liver lipid peroxidation (IC50 838.83 ± 1.18 µg/ml). The total phenolic content of SCA5 was 577.12 mg of GAE equivalents/gram extract. EA-SCA5 exhibited cytotoxic activity on A549 adenocarcinoma lung cancer cell line. It showed 84.9% activity at 500 µg/ml with IC50 value of 200 µg/ml. The gas chromatography mass spectrometry (GC-MS) analysis revealed the presence of one major bioactive compound actinomycin C2. CONCLUSIONS: The results of this study indicate that the EA-SCA5 could be probed further for isolating some medically useful compounds.