Computer-assisted Study of Garlic Organosulfur as Antioxidant Agents

Although many sulfur-containing garlic compounds exhibit antioxidant activity, little is known about the molecular mechanisms through which these compounds react with reactive oxygen species. For this reason, in this chapter, we present a summary of various papers in which, the scavenging of hydrogen peroxide and hydroxyl radical by garlic compounds allyl methyl disulfide, allyl methyl sulfide, and diallyl sulfide is analyzed from a theoretical-quantum outlook. Different computational methods and methodologies were analyzed. The DFT functional B3LYP, CAM-B3LYP, BKM, M05-2X, and M06-2X and even other methods such as Gaussian-n (G3MP2B3) were also evaluated. A broad series of basis sets were used from the simple 6-31G(d) to the extended triple-zeta 6-311++G(3df,2p). The thermodynamic and kinetic aspects of different proposed reactions were explored. Epoxidation, sulfonation, and hydrogenation were some of the processes raised as possible reaction pathways. Reaction mechanisms were proposed for each pathway, and different methods used to obtain the TS structure (TS Berny, QST2, and QST3) were compared. The kinetic and the rate constants were obtained through the Intrinsic Reaction Coordinate calculations. Gas and aqueous phases were mostly utilized in our papers; however, we included and studied the behavior of the systems in non-polar environments in our last publication. 

Keywords: Allyl methyl disulfide, Allyl methyl sulfide, Antioxidant activity, Diallyl sulfide, Density functional theory, Epoxidation, Garlic compounds, Hydrogenation, Hydroxyl radical, Hydrogen peroxide, IRC, Reactive oxygen species, Sulfoxidation.