Structure-radical scavenging activity relationships of hydroxytoluene derivatives

Research works proposed that radical scavenging activity of flavonoids is due to ring B, andthe remaining part of the molecule can be disregarded. Thus the objective of this work is toobserve whether hydroxytoluenes account the radical scavenging activity of flavonoid and toestablish structural requirements for their activity (as they showed appreciable activity) andelucidate a comprehensive mechanism that can explain their activity and termination. Thus, theradical-scavenging activity of nine hydroxytoluene derivatives against 2,2-diphenyl-1-picrylhydrazyl, DPPH was determined. The relative change in energy (ΔHf) associated with theformation of phenolic radicals and the spin distributions in these radicals were determined usingcomputational programs (Density function theory and Hartree Fock). By correlatingexperimental data with ΔHf, the most active compounds and structural features that areresponsible 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 themechanism of termination of most active hydroxytoluenes. Termination enthalpy (ΔH2) ofmethyl-catechols and methyl-hydroquinone, once the termination mechanism explained, wascalculated to understand its role in the radical scavenging activity.