Thermochemical behavior of sorghum procyanidin trimers with C4-C8 and C4-C6 interflavan bonds in the reaction with superoxide anion radical and H2O2-forming NADH-oxidase flavoenzyme

The thermochemical behavior of four sorghum procyanidin trimers (SPT) with C4-C8 and C4-C6 interflavan bonds, in the reaction with O-2(-) via the concerted double proton-transfer electron-transfer (CDPTET) and sequential proton-loss electron-transfer (SPLET) mechanisms, as well as with a H2O2-forming NADH-oxidase flavoenzyme, were analyzed by computational methods. Our results revealed that both CDPTET and SPLET mechanisms could be viable to develop in an aqueous medium. However, the free energies and rate constants of reaction showed that SPLET could be more favored. The SPT2 with interflavan bonds C4-C8 and C4-C6 in its most stable and predominant conformation (Compact-Extended), reached apparent rate constants of 1.07 x 10(6) (CDPTET) and 9.8 x 10(6) (SPLET) to scavenge the O-2(center dot-) in aqueous media. Likewise, SPT2 could prevent binding of NAD(P)H to the NADH-oxidase flavoenzyme, suggesting the greatest potential of this procyanidin to prevent the production and activity of the O-2(center dot-) in aqueous media.