Antimicrobial, antioxidant and cytotoxic properties of Streptomyces sp. (ERINLG-01) isolated from Southern Western Ghats

Objective: Streptomyces sp. is one of the most important antibiotic producing Gram positive bacteria. The aim of this study was to assess the antimicrobial, antioxidant and cytotoxic effects (against A549 lung adenocarcinoma cancer cell line) of ethyl acetate extract of Streptomyces sp. from the soil sample of Doddabetta forest, Nilgiris, Western Ghats of Tamil Nadu. Methods: Isolation of Streptomyces was performed by serial dilution plate technique. The strain was grown in MNGA medium to study the morphology and biochemical characteristics. Streptomyces sp. (ERINLG-01) was screened for its antimicrobial activity against pathogenic bacteria and fungi. The strain was subjected to 16S rRNA analysis and was identified as Streptomyces sp. (ERINLG-01). The nucleotide sequence of the 16S rRNA gene of the isolate exhibited close similarity with other Streptomyces sp. and has been submitted to Genbank. The antibacterial substances were extracted using ethyl acetate from MNGA medium. Antioxidant and cytotoxic effect were also studied. Results: Streptomyces sp. ERINLG-01 was isolated from the soil sample of the Doddabetta forest, Nilgiris, Tamil Nadu, India. Seven RAPD primers were tested against the DNA extracted from the Streptomyces sp.; four of them (OPA2, OPA9, OPN15 and OPA20) gave clear and scorable profiles. The ethyl acetate extract showed antimicrobial activity against six Gram negative, five Gram positive bacteria and three fungi. The zones of inhibitions were: 16 mm against B. subtilis, S. epidermidis and M. pachydermatis, 15 mm against E. aerogenes and C. albicans. The minimum inhibitory concentration values of ethyl acetate extract were: 125 μg/mL against B. subtilis, 250 μg/mL against S. epidermidis, M. pachydermatis, E. aerogenes and C. albicans. The radical scavenging activity was maximum at 1000 μg/mL (76.11%). Cupric Ion Reducing Antioxidant Capacity of ethyl acetate extract was dependent on the concentration. Ferric reducing antioxidant power assay of ethyl acetate extract showed (1.358 ± 0.04 mM Fe (II)/g) two-fold higher value compared to the standard. Ethyl acetate extract showed 82.4% cytotoxic activity in vitro against A549 lung adenocarcinoma cancer cell line at a dose of 1000 μg/mL with IC50 value of 600 μg/mL. The results showed that the ethyl acetate extract of Streptomyces sp. ERINLG-01 could be probed further in drug discovery programme. Conclusion: Streptomyces sp. ERINLG-01 showed promising antibacterial, antioxidant and cytotoxic activities.