Structure-radical scavenging activity relationships of hydroxytoluene derivatives

Research works proposed that radical scavenging activity of flavonoids is due to ring B, and the remaining part of the molecule can be disregarded. Thus the objective of this work is to observe whether hydroxytoluenes account the radical scavenging activity of flavonoid and to establish structural requirements for their activity (as they showed appreciable activity) and elucidate a comprehensive mechanism that can explain their activity and termination. Thus, the radical-scavenging activity of nine hydroxytoluene derivatives against 2,2-diphenyl-1- picrylhydrazyl, DPPH was determined. The relative change in energy (ΔHf) associated with the formation of phenolic radicals and the spin distributions in these radicals were determined using computational programs (Density function theory and Hartree Fock). By correlating experimental data with ΔHf, the most active compounds and structural features that are responsible for their activities were identified. Reaction product of 4-methyl catechol with 2,2- diphenyl-1-picrylhydrazyl, DPPH was isolated and characterized in order to unravel the mechanism of termination of most active hydroxytoluenes. Termination enthalpy (ΔH2) of methyl-catechols and methyl-hydroquinone, once the termination mechanism explained, was calculated to understand its role in the radical scavenging activity.