Bioassay-guided fractionation and in vitro and in silico biological activities of 2,4-di-tert-butylphenol isolated from Nocardiopsis sp. strain LC-8

In this study, an actinomycete strain was isolated from freshwater soil sediments to produce bioactive metabolite with a broad array of biological activities. Initially, preliminary antibacterial screening of isolate was performed by perpendicular streak method which showed the growth inhibition of all tested bacterial pathogens. Based on the culture characteristics, morphological identification, and 16S rRNA gene sequencing, the isolate was identified as Nocardiopsis sp. strain LC-8. Ethyl acetate extract of strain LC-8 showed potential antibacterial activity against tested bacterial pathogens with a maximum zone of inhibition of 16.98±0.57 mm against Staphylococcus aureus. After column chromatography, fraction 2 (F2) of the extract exhibited prominent growth inhibition activity against all tested bacterial and fungal pathogens. Antioxidant activity of F2 showed potent free radical scavenging activity with low IC₅₀ values (DPPH - 278.15±0.35 μg/mL, ABTS - 367.55±1.13 μg/mL, and FRAP - 347.48±1.35 μg/mL). Total phenolic content of F2 was quantified as 362.44±1.25 mg gallic acid equivalent/gram extract. As per spectral analyses, the isolated compound from F2 was identified as 2,4-di-tert-butylphenol which further induced cytotoxic (IC₅₀ value - 17.5±1.5 μg/mL) and apoptosis activity against MCF-7 cells. Molecular interaction studies of 2,4-di-tert-butylphenol with target proteins of pathogens and cancer cells displayed good docking score values. Finally, molecular dynamics simulation was performed to determine the stable structure of the protein-ligand system and effectiveness of 2,4-di-tert-butylphenol against the target protein. In conclusion, Nocardiopsis sp. strain LC-8 may act as a promising source for the production of 2,4-di-tert-butylphenol aiding diverse therapeutic roles.