Electrochemical Determination Of Superoxide Dismutase (sod) Activity

There is no doubt that oxygen species occur in biological systems. Superoxide anion radical(O2 ) and hydroxyl radical (HO) are typical ones.They are presumed to play an important role in a number of biological phenomena such as aging, oronary heart disease rheumatoid arthritis, cancer and other pathological conditions. These free radical are controlled in biological systems by some enzymes possessing antioxidant activities such as superoxide dismutase(SOD) and peroxidase (PO). It is well known that non-enzymatic substances such as vitamins, Chinese Traditional and Herbal Drugs (CTHD) and flavonoids, also scavenge free radical. Recently, the importance of removing excessive active oxygen species from living organisms is becoming increasing recognized, together with a growing interest in finding antioxidants that can scavenge the free radicals. Hence the determination of SOD activity and the study of scavenging activity of the antioxidants are necessary. Here we present four simple and rapid methods for the determination of SOD activity. This thesis research includes four parts and the main results could be expressed as follows:1. The relation between active oxygen radical and illness, superoxide dismutase and superoxide anion radical were introduced. The recent advance of determination of SOD activity and scavenging active oxygen radical by CTHD in the world were summarized.2. In the buffer solution of Na₂CO₃-NaHCO₃(pH 8.9), the current of the palladium( II) -8-hydroxyquinoline-5-sulfonic acid (8-OXSA) system with an anionic surfactant , sodium dodecyl sulfate(SDS) was increased markedly compared to that obtained without SDS. The reaction mechanism was related to the formation of superoxide anions radical (O₂ ). Polaragraphic determination of superoxide dismutase activity and the study of scavenging of superoxide anions by flavonoids was described which is based on that superoxide dismutase(SOD) catalyzed the dismutatiom of superoxide radical and reduced the peak current of the 8-OXSA-SDS system .3. In an alkaline medium , hydroxylammoniumchloride reacted with oxygen to form superoxide radical and was oxided to nitrite ion. At low pH with thiocyanate as catalyst, nitrite ion reacted rapidly and quantitatively with diphenylamine or diphenylamine-4-sulfonic acid toform nitrate complex with electrochemical activity, which gave sensitive second-order derivative reduction wave with the peak potentials of -0.67V and -0.60V(SCE) . Under the certain conditions the peak current was directly proportional to the concentration of nitrite ion. Superoxide dismutase enzyme catalyzed the dismutation of superoxide radical(O₂ )into H₂O₂ and O₂,The system with SOD inhibited the formation of nitrite ion. The electrochemical method for determination of SOD activity which was based on the detection of the formation of nitrite ion during autoxidation of hydroxylammoniumchloride was described. The curve of the SOD activity was detected. The method has been applied into the research of scavenging activity of some flavonoids.4. In a weakly alkaline medium , pyrogallol reacted with oxygen to form superoxide radical and several intermediate products which gave two waves and the peak potentials were - 0. 96V and -1.44V (SCE) . In Tris-HCl (pH8.30) buffer solution, the mechanism of the autoxidation of pyrogallol and the optimum experimental conditions were investigated. Superoxide dismutase enzyme catalyzed the dismutation reaction of superoxide radical so that dicreased the ratio of pyrogallol autoxidation, which could determinate superoside dismutase enzyme activity by detect the chang of the ratio of the pyrogallol autoxidation in with different SOD .A simple and sensitive electrochemical method was discribed. The method has been applied into the research of scanvenging activity of some flavonoids .The results indicated that the sensitivity of determination of SOD activity in -0.96V was better than in -1.44V.The results of four methods were summarized .The mechanism of scavenging active oxygen radicals by flavonoids , th...