Researches On The Structure And Antioxidant Activity Of Quercetin-Cr(Ⅲ) Ion Complex

Reactive oxygen species (ROS) include oxygen free radicals and peroxides related to oxygen metabolism in vivo. ROS play an important role in the vital activity for taking part in many vital processes and maintaining the normal metabolism, However, they can also attack biomoleculars and organelles, which will result in organism oxidative damages and consequently cause many diseases. Researches show that the exogenous antioxidants can scavenge the excess free radicals and cure many diseases induced by free radicals. Thus, evaluating and developing novel antioxidant is becoming one of the hot topic in the medicinal field recently. As an important natural flavonol antioxidant, quercetin is widely used in food and medicinal industries. It has been proved that quercetin can exert antioxidant ability through H atom transfer mechanism, and also can chelate metal cations to reduce the hydroxyl radical (·OH) caused by Fenton reaction.In this article, the structure, antioxidant activity and antioxidant mechanism of quercetin-Cr(III) ion complex are studied by using both theoretical and experimental methods. The main content of this article can be divided into three parts. The contribution of the author is summarized as following:(1) This article confirms that Cr(III) ion can participate in a Fenton-like reaction to generate hydroxyl radical (OH), thus induce the oxidative damage to DR and DNA. Meanwhile, the inhibition function of quercetin is measured, which prove that quercetin is a strong radical scavenger and antioxidant.(2) Quercetin-Cr(III) ion complex is synthesized and the structure is confirmed by IR, UV-vis methods. In addition, DFT method is used to compute the total energy (TE) and binding energy (BE) of many different potential complexes formed at different sites, thus to confirm the exact chelating site and the accurate form of the two reactants, laying a foundation for the further studies.(3) The antioxidant activity of quercetin-Cr(III) ion complex is analyzed based on the structural studies. Firstly, DPPH radical scavenging analysis is performed to compare the radical scavenging ability of quercetin and quercetin-Cr(III) ion complex. In order to complement the experimental study, DFT method is applied to compute the bond dissociation enthalpy (BDE) and ionization potential (IP) of quercetin and quercetin-Cr(III) ion complex to compare their antioxidant activities, also to make sure their antioxidant mechanisms.