Comparison between antioxidant activity of 2,5-disubstituted 1,3,4-oxadiazoles containing heteroaromatic ring and aromatic ring at 2nd position

A series of 4-[5-(substitutedphenyl)-1,3,4-oxadiazol-2-yl]-pyridine) and 2-[5-substitutedphenyl)-1,3,4-oxadiazol-2-yl]-benzenamine derivatives were synthesized from substituted esters and hydrazine hydrate in the presence of ethanol to give isonicotinic acid hydrazide and 2-aminobenzohydrazide followed by reaction with phosphorus oxychloride and various aromatic acids. All the compounds were tested for their in vitro antioxidant activity by 1,1-diphenyl-2-picryl hydrazyl (DPPH) method. Compounds containing aromatic group at 2nd position showed significant activity as compared to standard (ascorbic acid) which concludes that the presence of aromatic group increases the free radical scavenging activity.