The surrounding environments on the structure and antioxidative activity of luteolin.

Luteolin is an excellent antioxidant found in a wide variety of natural foods, such as honey and pollen. In this work, the effect of the surrounding environments on the structure and antioxidative activity of luteolin was carried out using density functional theory (DFT) calculation. The studied environments are gas, benzene, chloroform, pyridine, acetonitrile, ethanol, DMSO, and water. The structure of the luteolin monomer in different environments was optimized. The hydrogen-bond was especially focused, and the antioxidative capacity of luteolin was analyzed from the thermodynamic aspect. It is found that: (1) hydrogen atom transfer (HAT) is the most thermodynamically favorable mechanism in the gas, benzene, and chloroform phases, while sequential proton loss electron transfer (SPLET) is more favorable than HAT and single electron transfer followed by proton transfer (SET-PT) in pyridine, acetonitrile, ethanol, DMSO, and water phases. (2) The 4'-OH group could more strongly participate in the free radical scavenging process of luteolin than other OH groups, while the 5-OH group is the least favored one in the studied environments. (3) The antioxidative capacity of luteolin is strongest in pyridine.