Antimicrobial and cytotoxicity properties of 2,3-dihydroxy-9,10-anthraquinone isolated from Streptomyces galbus (ERINLG-127).

Streptomyces galbus ERINLG-127 was isolated from the soil samples of the Marapalam forest, Nilgiris, India. The ethyl acetate extract was subjected to activity-guided fractionation by column chromatography over silica gel. This led to the isolation of 2,3-dihydroxy-9,10-anthraquinone as the active principle. The compound showed good antimicrobial activity against tested bacteria and fungi. The minimum inhibitory concentration values of isolated compound were 12.5 μg/mL against Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella typhimurium, K. pneumoniae (ESBL-3971), K. pneumoniae (ESBL-3894) and Staphylococcus aureus (MRSA). The compound showed prominent cytotoxic activity in vitro against A549 lung adenocarcinoma cancer cell line. It showed 75.1 % activity at the dose of 100 μg/mL with IC50 value of 60 μg/mL. The isolated compound was subjected to molecular docking studies for the inhibition of TtgR and Topoisomerase IV enzymes which are targets for antimicrobials. Docking studies of the compound showed low docking energy indicating its usefulness as antimicrobial agent.