Studies Of Anti-radicals Activity On Luteolin And Its Tin Complex

The work was based on the accumulation research of flavonoids compounds in our group. The coreresearch object was luteolin. The mechanism of DPPH· free radical scavenging of luteolin was studied bymeans of various chemical analysis techniques. According to the current research of metal complexes, thesynthesis process of luteolin and stannum (II) coordination compound was studied. The complex wasanalyzed by means of UV-Vis spectrometry, infrared spectrometry (IR), nuclear magnetic resonancespectrometry (NMR) and thermal gravimetric analysis (TGA). Furthermore, the anti-radical activities ofluteolin and its stannum(II) complex on DPPH· and·OH free radicals were analyzed comparatively. Theresults provide theoretical foundation and practical values for further development and utilization offlavonoids compounds. The main contents are as follows:1. Review on natural medicines and its antioxidative complexesThe current research and achievements were reviewed mainly from the following three aspects:(1)Main ingredients and their activities of natural medicines, as well as the current three basic judgments ofthe effective ingredients of natural medicine were summarized.(2) The compounds which can scavengefree radicals, the methods which were used to estimate the free radical scavenging activity in vitro, and themechanism of free radicals scavenging of natural compounds were reviewed.(3) The types of functionalcomplexes and their corresponding activities in recent years were also reviewed. Then the reaearch subjectwas put forward on this basis.2. The study of DPPH· radical scavenging mechanism of luteolinThe mechanism of DPPH· radical scavenging of luteolin was researched by UV-Vis spectrometry,cyclic voltammetry spectrometry (CV), mass spectrometry (MS) and nuclear magnetic resonancespectrometry (NMR). The results showed that DPPH· radical scavenging proceed through an H-Protontransfer (HAT) mechanism which the H-Proton of phenolic hydroxyl groups of luteolin transferred toDPPH· free radicals. After donated H-Proton, luteolin radical gained other hydrogen from the surroundingand returned to luteolin. And the study also showed that the intermolecular condensation didn’t take place. 3. The synthesis process of luteolin and stannum(II) complexAccording to the recent research reports about luteolin and metal ion complexes, the synthesis processof luteolin and stannum(II) coordination compound was researched on the basis of preliminary work. Thesynthetic process was researched by UV-Vis spectrometry through four aspects namely pH of reactionsolution, molar ratio of the reactants, temperature and reaction time. And the4factors3levels oforthogonal test was designed in order to get the optimum technological conditions. The results showed thatthe optimum technological conditions of luteolin and Stannum (II) complex were at the conditions of pH4.5, molar ratio of luteolin and stannous chloride1:2.5, temperature35oC and5h. The remarkable impactfactor to the complex synthesis was the pH of reaction solution, the second factor was reaction time, themolar ratio of raw material and temperature were the least significant. The yield was75.14%at the optimalconditions.4. The characterization and anti-radical activity of stannum(II)-luteolin complexThe characterization of stannum(II)-luteolin complex was analyzed by means of UV-Vis spectrometry,infrared spectrometry (IR), nuclear magnetic resonance spectrometry (NMR) and thermal gravimetricanalysis (TGA). The anti-radical activities of luteolin and its stannum(II) complex on savengingDPPH· and·OH free radicals were also studied. The results suggested that the coordination sites of luteolinwith stannum (II) cations were at5-hydroxy and4-carbonyl, and3′,4′-dihydroxyl (catechol). The complexwas stable and its decomposition temperature was500~600oC. Luteolin-Sn (II) complex showed weakeranti-radical activity than luteolin, which was due to the complexation of Sn (II) with the active site at5-OHand4-C=O, and3′,4′-OH in the molecule of luteolin. And it was also proved indirectly that luteolinscavenged DPPH· radical mainly through the contribution of hydrogen of the phenolic hydroxyl groups.