Comparative Investigation on Radical Scavenging Activity and Protective Properties of Natural Isolated and Synthetic Antioxidants

The purpose of this study is to evaluate and compare the free radical scavenging activity and protective properties of the natural product SQGD-IBG-21 isolated from a radioresistant bacterium Bacillus sp. INM-1 and synthetic nitroxyl free radical containing antioxidant 1-ethyl-1-nitroso-3-[4-(2,2,6,6-tetramethylpiperidine1-oxyl)]-urea (SLENU). It was found a higher reducing power potential for SQGD (1.336±0.03357 Uabs) comparing to that of SLENU (0.196±0.002273Uabs); a higher nitric oxide radical scavenging activity 35.645 ±1,122% for SQGD in comparison with SLENU (19.964±2.233%). Total antioxidant capacity of SQGD was found to be 75±0.06%, while for SLENU it was only 22±0.03%. Maximum protection to the liposomes calculated in % inhibitory activity of two agents was found to be 50.04±0.037% for the natural agent and 27.54±0.33% for nitroxyl–labeled agent. By direct EPR spectroscopy stable radical structures were recorded in the solutions of both studied antioxidants: an o-semiquinone radical structure was recorded in aqueous solution of SQGD and nitroxyl free radical struture in the ethanol solution of SLENU, respectively. It should be mentioned that the natural antioxidant possesses higher protective properties in comparison with the synthetic antioxidant. In conclusion, because of well expressed free radical scavenging and antioxidant activities of both studied agents they might be used in the combination anticancer chemotherapy for reduction the toxicity caused by anticancer drugs and/or radiation therapy.