Abstract
An endophytic bacterium was isolated from the Chinese medicinal plant Artemisia annua L. The phylogenetic and physiological characterization indicated that the isolate, strain SZ-1, was Bacillus cereus. The endophyte could produce an exopolysaccharide (EPS) at 46 mg/L. The 1,1-diphenyl-2-picrylhydracyl (DPPH) radical scavenging activity of the EPS reached more than 50% at 3–5 mg/mL. The EPS was also effective in scavenging superoxide radical in a concentration dependent fashion with an EC50 value of 2.6 mg/mL. The corresponding EC50 for scavenging hydroxyl radical was 3.1 mg/mL. Moreover, phenanthroline-copper complex-mediated chemiluminescent emission of DNA damage was both inhibited and delayed by EPS. The EPS at 0.7–1.7 mg/mL also protected supercoiled DNA strands in plasmid pBR322 against scission induced by Fenton-mediated hydroxyl radical. The preincubation of PC12 cells with the EPS prior to H2O2 exposure increased the cell survival and glutathione (GSH) level and catalase (CAT) activities, and decreased the level of malondialdehyde (MDA) and lactate dehydrogenase (LDH) activity in a dose-dependent manner, suggesting a pronounced protective effect against H2O2-induced cytotoxicity. Our study indicated that the EPS could be useful for preventing oxidative DNA damage and cellular oxidation in pharmaceutical and food industries.
Highlights
Free radicals such as superoxide, hydroxyl radical and other reactive oxygen species (ROS) are associated with cellular necrosis and a variety of pathological conditions such as cancer, degenerative disease in neurons, hepatopathies, antherosclerosis, and even aging [1]
Liu et al reported for the first time, the capacity of the bacterium endophyte Paenibacillus polymyxa to produce EPS with strong scavenging activities on superoxide and endophyte metabolites including phenolic compounds and flavonoids can be a potential source of hydroxyl novelradicals natural antioxidants
The EPS from endophytic Bacillus possessed the antioxidant activity in vitro, our results suggested a possibility that the endophyte could change the cellular redox status by released EPS and is most probably associated with the strong adaptability and competitiveness of host A. annua in nature [27]
Summary
Free radicals such as superoxide, hydroxyl radical and other reactive oxygen species (ROS) are associated with cellular necrosis and a variety of pathological conditions such as cancer, degenerative disease in neurons, hepatopathies, antherosclerosis, and even aging [1]. Antioxidants, scavenging free radicals, are known to play important roles in preventing the ROS-linked diseases [2]. Some bacterial exopolysaccharides (EPS) have been demonstrated to possess potent antioxidant activities and applications as natural antioxidants [6,7]. It has been reported that endophyte metabolites including phenolic compounds and flavonoids can be a potential source of novelMolecules natural antioxidants [9,10]. Liu et al reported for the first time, the capacity of the bacterium endophyte Paenibacillus polymyxa to produce EPS with strong scavenging activities on superoxide and endophyte metabolites including phenolic compounds and flavonoids can be a potential source of hydroxyl [11]
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