Isolation of potential anti-microbial compounds from actinomycetes found in soil surrounding medicinal plants of Saurashtra, Gujarat, India.

Objectives: Resistance developed by micro-organisms against antibiotics is now a global threat. There is a need to look at alternate sources from which substances useful against various diseases can be obtained. Soil surrounding the medicinal plants possessing anti-microbial activity was screened to find soil bacteria capable of producing anti-microbial compounds and to isolate such compounds therefrom. Materials and Methods: Eleven anti-microbial medicinal plants from three regions of Saurashtra, Gujarat, India, were selected, and soil surrounding those plants was collected. Sixty-six isolates of actinomycetes were obtained from the soil samples. Cross streak, agar well, and disk diffusion methods were used for primary, secondary, and final screening, respectively, of the anti-microbial isolates. Results: Among all, the isolate from the soil surrounding Ocimum sanctum in the Gir-Somnath region was found to be most potent and subjected to thin-layer chromatography, bio-autography, bio-chemical tests, enzymatic activity, 16S rDNA sequencing, and gel electrophoresis, which was confirmed to be Streptomyces arenae, followed by optimization of various conditions. Isolation and characterization of the compound were performed by using ultra-violet, Fourier transform infrared, nuclear magnetic resonance, and mass spectroscopy. A novel compound was isolated and characterized, which showed potent anti-microbial activity as compared to reference standards by in vitro anti-microbial assay. Conclusion: Soil surrounding medicinal plants which themselves have well-known anti-microbial activity may be a rich source of actinomycetes, which may produce compounds having anti-microbial properties. This can be an emerging strategy for researchers and clinicians to explore soil bacteria for the isolation of biologically active compounds for the management of various diseases. [ABSTRACT FROM AUTHOR]