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Theoritecal Investigation of Kinetics and Thermodynamic of Vitamin Antioxidants Reaction Mechanism, in Particular Vitamin C, with Free Radicals
, M.Sc. Thesis Sharif University of Technology ; Gholami, Mohammad Reza (Supervisor)
Abstract
Antioxidants are compounds which prevent free radicals from aggregation and formation in body cells. vitamin C, E and carotene are among the most important antioxidant that have reduction properties. free radicals have great chemical reactivity which can react with different types of compound in human body such as lipids, cell membrane and proteins and cause different illnesses. Antioxidants with various mechanisms such as hydrogen atom transfer, single electron transfer SPLET, sequential proton loss electron transfer and radical adduct formation can stable free radicals and also become non-active compounds, antioxidant properties of these compounds related to structure and their functional...
The Study of Antioxidant Mechanism of some Flavonoids without and in Presence of Cyclodextrins: Theoretical Point of View
, Ph.D. Dissertation Sharif University of Technology ; Tafazzoli, Mohsen (Supervisor) ; Ghiasi, Mina (Co-Supervisor)
Abstract
Antioxidants are compounds with anti-cancer, anti-bacterial, anti-viral, anti-aging and anti-allergic properties. In the present study, a quantum mechanical approach has been used to shed light on the presence effect of glycoside group on the antioxidant ability of chrysin as one of the most important consumable flavonoids and two glycoside derivatives, chrysin-6-C-fucopyranoside and chrysin-3-malonyl-6-C-fucopyranoside which has electron-withdrawing group (EWG) in its C3 of glycoside group. Density functional theory (DFT) using B3LYP and UB3LYP functional and split-valance 6-311++G ** basis set were used to optimize chrysin, its different derivatives, and their radicals. Analysis of...
A quantum chemical study on the OH radical quenching by natural antioxidant fisetin
, Article Journal of Physical Organic Chemistry ; Volume 30, Issue 11 , 2017 ; 08943230 (ISSN) ; Fattahi, A ; Sharif University of Technology
Abstract
In this work, the antioxidant ability of fisetin was explored toward hydroxyl (•OH) radical in aqueous and lipid solution using density functional level of theory. Different reaction mechanisms have been studied: hydrogen atom transfer, single electron transfer followed by proton transfer, and radical adduct formation, and sequential proton loss electron transfer. Rate constants for all possible reaction sites have been calculated using conventional transition state theory in conjunction with the Collins-Kimball theory. Branching ratios for the different channels of reaction are reported for the first time. Results show that the reactivity of fisetin toward hydroxyl (•OH) radical takes place...
The free radical scavenging activity of lespedezacoumestan toward ˙OH radical: a quantum chemical and computational kinetics study
, Article Journal of Physical Organic Chemistry ; Volume 31, Issue 2 , February , 2018 ; 08943230 (ISSN) ; Fattahi, A ; Sharif University of Technology
John Wiley and Sons Ltd
2018
Abstract
The free radical activity of lespedezacoumestan was investigated toward hydroxyl (˙OH) radical in polar and nonpolar media using density functional theory. Four reaction mechanisms including radical adduct formation, hydrogen atom transfer, sequential single electron-proton transfer (SET-PT), and sequential proton loss electron transfer were considered. The rate constants and branching ratio for all possible sites of reaction were calculated and reported for the first time. According to the obtained results, lespedezacoumestan reacts faster with ˙OH radical in aqueous solution than in nonpolar media. Also, lespedezacoumestan is an excellent ˙OH radical scavenger regardless of the environment...