Study On The Capacites Of Antioxidants Containing Hydroxyl, Thiol And Amine

Nowadays, biological antioxidation as the figure field of research in physical organic chemistry has been paid more attention. Researchers widely concern the comprehensiveness in their research now, one is exploring new antioxidants. the other is improving the system to evaluate the abilities of antioxidants.Presently, the methods to evaluate abilities of antioxidants are dividing into two classes, one is chemical system, the other is biological system. There are 2,2'-diphenyl-l-picrylhydrazyl radical (DPPH),2.2'-azinobis(3-ethylbenzo thiazoline-6-sulfonate) cation radical (ABTS+) and galvinoxyl radical methods in chemical system, which are found usually exhibit different activity of antioxidants to those methods in biological system because the test conditions in these two systems are also different, though they can give the quantitative results of activity of antioxidants quickly and accurately. Accordingly, there are 2.2'-azobis(2-ami dinopropane hydrochloride) (AAPH) induced oxidation of DNA. hemolysis, Hemin induced hemolysis, Cu2+/glutathione (GSH)-, and hydroxyl radical (·OH)-induced oxidation of DNA methods in biological system. Because of the methods in this system having no quantitative standard, they cannot evaluate the activity of antioxidants accurately, though they can overcome the disadvantages of chemical system. In this paper, it is attempted to combine the chemical system and biological system to evaluate antioxidants all-sidedly and systematically, and also introduce chemical kinetics equations in the latter to give a quantitative standard to evaluate the activity of antioxidants. The figure content of the work in this paper is as follows.1.The study on abilities of natural and synthetic antioxidants containing-OH groupFirstly, from the natural compounds icariin, we did the research on its antioxidant ability in the AAPH-induced oxidation of DNA. It was found that it can reduce the production of thiobarbituric acid reactive substance(TBARS) obviously, demonstrating its activity to against oxidation of DNA. Then we designed and synthesized eighteen Schiff bases with various substituents and tested their antioxidant abilities using the same methods. The results exhibited there were two antioxidation mechanisms.6 of these Schiff bases inhibited the oxidation of DNA via slowing down the rate of production of TBARS, while the other 12 Schiff bases could give inhibition time in the process. We can calculate the numbers of antioxidants to capture free radicals by introducing chemical kinetics equations in order to compare their antioxidant activity quantitatively. The result was the Schiff base without substituent also had antioxidant capacity in this system. The activity of phenolic hydroxyl groups in imido group side were higher than those in methylene group side.The activity of hydroxyl groups in ortho-position of N atom were lower than those in para-position of N atom because of the influence of the position of hydroxyl group and steric inhibition of resonance.Secondly, we designed and synthesized eight ferrocenyl hydroxyl compounds 2-ferrocenyl-1-(3-hydroxyphenyl)-1-phenyl-but-1-ene(FP3),2-ferrocenyl-1-(4-hydr oxyphenyl)-1-phenyl-but-1-ene(FP4),2-ferrocenyl-1-(3,4-dihydroxyphenyl)-1-phenyl-but-1-ene(FP34),2-ferrocenyl-1,1'-bis(4-hydroxyphenyl)-but-1-ene(FP44), 2-ferrocenyl-1-(3-hydroxyphenyl)-1-phenyl-phenylthylene(FB3),2-ferrocenyl-1-(4-hydroxyphenyl)-1-phenyl-phenylthylene(FB4),2-ferrocenyl-1-(3,4-dihydroxyphen yl)-1-phenyl-phenylthylene(FB34),2-ferrocenyl-1,1'-bis(4-hydroxyphenyl)-phenyl thylene(FB44) and tested their antioxidant abilities in capturing ABTS+radical. protecting DNA against AAPH and Cu2+/GSH-induced oxidation. The results demonstrated that all of the eight compounds can exhibit strong reduction activity in capturing ABTS+ radical, and more, the reduction activity of monohydroxyl compound FB4 and dihydroxyl compounds FP34, FP44. FB44, FB34 were stronger than FP3, FP4. FB3. while all of the eight compounds exhibited prooxidant effect in Cu2+/GSH-induced oxidation of DNA. Monohy-droxyl compounds can slow down the rate of production of TBARS while dihydroxyl compounds FP44, FB44, FB34 and FP34 can capture 11.9,7.1.6.2 and 4.9 radicals respectively in AAPH-induced oxidation of DNA and the sequence is FP44>FB44>FB34>FP34 in this system.2. Study on antioxidant abilities of compounds containing-SHThe abilities of dihydrolipoic acid (DHLA) to scavenge peroxynitrite (ONOO-). galvinoxyl radical,2.2,-azinobis(3-ethylbenzothiazoline-6-sulfonate) cation radical (ABTS+), and 2,2"-diphenyl-l-picrylhydrazyl radical (DPPH) were higher than those of lipoic acid (LA). The effectiveness of DHLA to protect methyl linoleate against 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)-induced oxidation was higher than that of LA, and LA even played a role in prooxidation in theβ-carotene-bleaching test. Moreover, DHLA can scavenge～2.0 radicals in AAPH-induced oxidation of DNA and～0.26 radicals in AAPH-induced hemolysis of erythrocytes, whereas LA can scavenge～1.5 radicals and-0.18 radicals at the same experimental conditions, implying that DHLA and LA are more conducive to inhibit AAPH-induced oxidation of DNA. We also found that a certain concentration of DHLA, GSH and Cu(Ⅱ) coexist can accelerate the degradation of DNA. We made a mixture of in order to study LA, DHLA and standard antioxidants VE, VC synergy between the protective role of red blood cells. We found that the activity of the mixedm-ode DHLA is also stronger than LA, and DHLA can repair VC when mixed with VC. DHLA and LA are able to protect the red blood cells as a membrane stabilizer in Hemin-induced hemolysis of erythrocytes. 3. Study on antioxidant abilities of compounds containing-NH2,3-dimethyl-indole(DMI),5-methoxy-2,3-dimethyl-indole(MDI),2,3,4,9-tetrahydro-carbazole(THC) and 6-methoxy-2,3,4,9-tetrahydro-carbazole (MTC) were designed and synthesized, the antioxidant properties of 6 compounds contained the four kinds of indole derivatives, indole(IND) and melatonin(MLT) were compared. It was found that IND was less active to trap ABTS+ and DPPH, but introduction of different substituents in 2,3,5-position, provided direct evidence for these indole derivatives to scavenge radicals and emphasized the importance of electron-donating groups for the free radical-scavenging activity of indole derivatives. The antioxidant mechanism shown by the IND is different from that of other five indole derivatives in AAPH-induced oxidation of DNA. The ranking of antioxidant activity is MTC=MLT>THC>DMI=MDI. The ranking of antioxidant activity is MTC>IND>THC>DMI≈MDI>MLT in AAPH-induced hemolysis of erythrocytes.