Novel aromatic polyketides from soil Streptomyces spp.: purification, characterization and bioactivity studies

Area of Science:

• Microbiology and Biotechnology
• Natural Products Chemistry
• Pharmacology

Background:

• Aromatic polyketides are crucial therapeutic compounds, with many derived from soil-dwelling Streptomyces.
• The isolation and characterization of novel polyketides are vital for discovering new therapeutic agents.
• Streptomyces species are a rich source of bioactive secondary metabolites.

Purpose of the Study:

• To isolate and identify potent aromatic polyketide-producing Streptomyces strains from soil.
• To characterize the chemical structures of isolated polyketides.
• To evaluate the bioactivity, including antimicrobial and anticancer properties, of these compounds.

Main Methods:

• Isolation of 54 Streptomyces strains from soil samples.
• Identification of potent producers using 16S rRNA gene sequencing.
• Cultivation under optimized conditions, followed by chromatographic fractionation (silica gel column, preparative TLC) to obtain pure compounds.
• Structure elucidation using UV-Vis, IR, and NMR spectroscopy.
• Bioactivity testing, including Minimum Inhibitory Concentration (MIC) against Bacillus cereus and IC50 against HeLa cells.

Main Results:

• Five potent aromatic polyketide-producing strains were identified: Streptomyces spectabilis (R1), S. olivaceus (B1), S. purpurascens (R3), S. coeruleorubidus (R5), and S. lavendofoliae (Y8).
• Isolated compounds included dihydrodaunomycin (MIC 4 µg/ml, IC50 24 µM), rhodomycin (MIC 2 µg/ml, IC50 15 µM), daunomycin (IC50 10 µM), and a novel aclacinomycin analogue (IC50 2.9 µM).
• Several compounds exhibited significant antimicrobial activity and potent anticancer properties, including antimetastatic effects against HeLa cells.

Conclusions:

• This study successfully isolated and characterized several potent aromatic polyketides from soil Streptomyces species.
• The identified compounds, particularly rhodomycin and the novel aclacinomycin analogue, show promising therapeutic potential.
• These findings highlight the importance of exploring soil microorganisms for novel chemotherapeutic drug development.