Abstract
BACKGROUND: Actinomycetes are soil-dwelling microorganisms known for the production of natural pigments, which serve as alternatives to synthetic dyes. In this study, the effects of natural light and total dark conditions on pigment production in Streptomyces sp. VITGV38 (MCC 4869) were examined, and the extracted pigment-related compounds were subjected to pharmacokinetic analysis, molecular docking studies, and evaluation of antioxidant and antibacterial activities. MATERIALS AND METHODS: The Streptomyces strain was cultured under complete darkness and natural (light/dark) conditions to compare pigment yield and bioactivity. Antioxidant activity of the crude pigment extract was determined by the DPPH free radical scavenging assay. Antibacterial activity of the pigment extract was tested against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Pseudomonas aeruginosa. Gas chromatography-mass spectrometry (GC-MS) was conducted to identify individual compounds of the pigment extract. Molecular docking of the pigment-related compounds was performed using AutoDock Vina, and their pharmacokinetic properties were predicted using SwissADME. RESULTS: After 21 days of culturing the strain under light conditions, the pigment extract at 100 µg/ml concentration showed the maximum antioxidant activity of 83.73% with an IC(50) value of 0.143 µg/ml, indicating strong antioxidant capacity. The antibacterial activity of the pigment extract was higher when the strain was cultured dark conditions. Gas chromatography-mass spectrometry analysis identified seven major compounds in the pigment extract: n-hexadecanoic acid, tetracosane, pentadecanoic acid, tetradecanoic acid, indole, benzo(h)quinoline-2,4-dimethyl, and 2-piperidinone. Molecular docking analysis revealed strong interactions of the pigment-related compounds with potential protein targets. SwissADME analysis showed that the pigment-related compounds have favorable drug-like properties. CONCLUSIONS: Streptomyces sp. VITGV38 is a promising source of bioactive pigments with potent antioxidant and antibacterial activities. While culturing the strain under natural light conditions enhanced the antioxidant capacity and yield of the pigment, culturing under dark conditions enhanced the antibacterial activity of the pigment. These findings highlight the multifaceted potential of Streptomyces sp. VITGV38 for developing natural antimicrobial agents.