Abstract
Context: Actinobacteria are a precious source of novel bioactive metabolites with potential pharmaceutical applications.Objectives: Representatives of 11 genera of rare Actinobacteria were selected for the evaluation of antioxidant activity.Material and methods: Fermentation broths of the Actinobacteria were extracted and dosage of 10 to 2000 µg/mL were applied for in vitro antioxidant-related bioassays. Cytotoxicity was assessed at the concentration of 2.5–20 µg/mL.Results: In the DPPH scavenging activity, 15 out of 52 extracts showed 17.0–26.8% activity in quantitative evaluation. Metabolites of five prominent antioxidant producing strains protected the DNA (pUC19) against UV-induced photolyzed H2O2-oxidative degradation. The potent antioxidant extracts inhibited two oxidative enzymes of xanthine oxidase in the range of 17.5–45.2% (three extracts had IC50 less than allopurinol) and lipoxygenase in the range of 36–55% (all five extracts had IC50 values less than daidzein). All these extracts could also protect eythrocytes from iron-induced hemolysis with ED50 values in a range of 0.014–1.25 mg/mL. Growth restoration of the yeast cells lacking the sod1 gene was observed by the antioxidant metabolite of Saccharothrix ecbatanensis UTMC 537 at the concentration of 1 mg/mL.Conclusions: The presence of nonidentical metabolites might be responsible for antioxidant and enzyme inhibitory activities of S. ecbatanensis, newly described actinobacterium in family Pseudonocardiaceae. The scavenging of the free electrons, protection of DNA and model yeast cells against oxidative stress, in addition to the inhibition of the oxidating enzymes are the main mechanisms of the antioxidant effect of the introduced resource in this study.
Highlights
Oxidative stress represents an imbalance between the production of reactive oxygen species (ROS) or oxygen radicals and the biological system’s ability to inhibit the reactive oxygen intermediates (ROI) or precursors of them, to alleviate the resulting damage (Baynes 1991)
Triplicate measurements were made and the ability to scavenge the DPPH radical was calculated by the following Formula 1, where A0 is the absorbance of the control and A1 is the absorbance of the sample
According to the intensity of yellow spots against a purple background or the frequency of yellow spots in an identical extract, 15 extracts were selected for quantitative DPPH assay
Summary
Oxidative stress represents an imbalance between the production of reactive oxygen species (ROS) or oxygen radicals and the biological system’s ability to inhibit the reactive oxygen intermediates (ROI) or precursors of them, to alleviate the resulting damage (Baynes 1991). Antioxidants can react with free radicals, scavenge them and inhibit oxidation created under physiological conditions, thereby function in prevention and treatment of the related diseases (Niki 2010). In order to reduce the ROS-induced oxidative damage, both synthetic and natural antioxidants are used. Synthetic antioxidants are strong radical scavengers, they usually have side effects, as the implication of tert-butylhydroquinone (TBHQ) in cancer has previously been reported (Hirose et al 1993). In order to protect against free radicals and retard the progression of many chronic diseases, the discovery of natural nontoxic antioxidants is demanded. Among Actinobacteria, the majority of the biologically active compounds have been discovered from the genus Streptomyces
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