The Potencies of Streptomyces-derived Biopigments as Antioxidant, Antibacterial and Anticancer Agents

Abstract

Actinomycetes, are known for their abilities to produce diverse secondary metabolites. About 100,000 active compounds of secondary metabolites are known to be produced by actinomycetes. This amount includes 45% of all active compounds of secondary metabolites produced by microorganisms. Streptomyces, one of the actinomycetes genus are able to produce various types of pigment. Pigments, as one of the secondary metabolites, have different biological activities such as antioxidant, anticancer, and antimicrobial activity. Soil actinomycetes ARK19 and ARK86 produced pink-purple and yellow intracellular pigment which potentially has pharmaceutical properties. Here, we assessed the antioxidant, antibacterial and anticancer activity of the crude pigment extract and its active fraction and the detection of polyketide synthases (PKS) and non-ribosomal peptide synthetases (NRPS) genes. In our study, ARK19 has the closest similarity with Streptomyces yangpuensis fd-2tb (99%). The actinomycetes showed the best growth and pigment production in ISP4 medium supplemented with starch as a carbon source. The pigment extracts were extracted using methanol solvent resulted yield 7.54% and 6.21% (w/w) for S. yangpuensis ARK19 and S. polychromogenes ARK86, respectively. Based on the UV-Vis analysis, the S. yangpuensis ARK19’s pink-purple pigment was indicated as prodigiosin, while the S. polychromogenes ARK86’s yellow pigment indicated as carotenoid. The crude pigment extracts were tested for their cytotoxic activity by Brine Shrimp Lethality Test (BSLT). The LC50 of each extract was recorded at 182.88 μg/ml and 116 μg/ml for S. yangpuensis ARK19 and S. polychromogenes, respectively. The result suggests that the pigment extracts were classified as a cytotoxic compound and might have anticancer activity. These findings were supported by a cytotoxicity test by MTT assay against a human breast cell line. S. polychromogenes crude pigment extract showed the best cytotoxic activity with an IC50 value of 289.07 μg/mL and 271.27 μg/mL for MCF-7 and MCF-12A cell lines, respectively. Furthermore, to understand the possible chemical compounds involved in their biological activities, we identified the chemical composition of the pigment extracts by GC-MS analysis. Our result revealed that the most dominant compound in the crude pigment extract were 6-Octadecanoid acid and 2-p-nitrophenyl-1,3,4-oxadiazol-5- in S. yangpuensis ARK19 and S. polychromogenes ARK86, respectively. The active fraction was obtained by Thin-Layer Chromatography separation. The antioxidant and antibacterial active fractions of the extracts was determined by bioautography test followed by preparative-TLC. Our result showed that the crude pigment extract as well as their active fraction have in vitro antioxidant activity against DPPH radical. The antibacterial activity was assayed by the disc diffusion method exhibited broad spectrum activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. The active fraction of S. polychromogenes ARK86 extract resulted changes in morphology of B. subtilis as a result of antibacterial activity. Metabolite profiling using LC-MS analysis showed that active fraction of S. yangpuensis ARK19 was rich in dextromethorphan, while S. polychromogenes ARK86 major compounds was morphine. This compound was reported to have anti-oxidative stress and antiproliferative activity. Moreover, PCR-based gene detection revealed the presence of marker genes of both PKS and NRPS clusters, the common secondary metabolite synthesis mechanism in microbes. The results showed that the crude pigment extract and the active fraction of S. yangpuensis ARK19 and S. polychromogenes ARK86 were a potential antioxidant, antibacterial and anticancer agents.