Synthesis of polyhydroxylated aromatic mandelic acid amides and their antioxidative potential

Six hydroxymandelic acid amides of phenolic amines were synthesized by condensation of 3,4-dihydroxymandelic or 4-hydroxy-3-methoxymandelic acid N-succinimidyl esters and several phenolic benzylamino and phenethylamino hydrochlorides in moderate to good yield. The radical scavenging activities determined by 2,2-diphenyl-1-picrylhydrazyl assay and superoxide trapping assay were superior compared to standards l-ascorbic acid, α-tocopherol, and butylated hydroxytoluene (BHT). The antioxidative activities tested by accelerated autoxidation of bulk lipids were 2–3.5 times more potent compared to standards α-tocopherol and BHT. 3,4-Dihydroxymandelic acid dopamide (4b) and 4-hydroxy-3-methoxymandelic acid dopamide (4a) showed the best overall performance as antioxidants.