Preparation of organic extracts
Organic extract of 131 isolates was prepared using ethyl acetate as solvent. Bacterial isolates for the production of secondary metabolites were prepared in basal medium. Briefly, 100 μl of bacterial inoculum (1.0 OD at 600 nm) prepared in basal medium was transferred into fresh medium (100 ml) and incubated at 28 ± 2 °C for 7 days in a rotary shaker maintained at 100 rpm. The supernatant from 7-day-old bacterial culture was mixed with equal volume of ethyl acetate and extracted by shaking at 180 rpm for 1 h. The ethyl acetate phase was separated and concentrated in a rotary evaporator under vacuum at 40 °C. The residue thus obtained was weighed, stock solutions prepared in DMSO and maintained at 4 °C till further use.