This research was aimed at synthesizing Mannich bases of piperidine and p-chloroaniline derivatives and investigating their antioxidant and antimicrobial activities since report has it that Mannich bases possessing electron withdrawing group show good anti-oxidant, antimicrobial, anti-cancer and anti-tumour properties. The synthesized compounds were characterized by Nuclear Magnetic Resonance (NMR), Infra red (IR) and Ultra/Violet-Visible (UV-V) spectroscopy. 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and Agar Well diffusion methods were used for the antioxidant and antimicrobial screening respectively.
Eight Mannich bases namely N,3-diphenyl-3-(piperidin-1-yl)propanamide (MB1), 3-((4-chlorophenyl)amino)-2-hydroxy-1,2,3-triphenylpropan-1-one (MB2), 2-((3-((4-chlorophenyl)amino)-3-phenylpropanoyl)oxy)benzoic acid (MB3), 3-(((4-chlorophenyl)amino)(phenyl)methyl)-5,7-dihydroxy-2-(4-hydroxyphenyl)chroman-4-one (MB4), 3-((4-chlorophenyl)amino)-3-(4-hydroxy-3-methoxyphenyl)-1-phenylpropan-1-one (MB5), 3-((4-chlorophenyl)amino)-N,3-diphenylpropanamide (MB6), benzoic 2-((4-chlorophenylamino)methyl)benzoic peroxyanhydride (MB7) and 3-(4-chlorophenylamino)-1,3-diphenylpropan-1-one (MB8) were synthesized. NMR confirmed the presence of the N-H aromatic stretch, in the range δ 4.00. IR also confirmed the presence of C=O, O-H and N-H typical of the Mannich bases. The Ultra/Violet-Visible absorption spectra for the synthesized compounds revealed that the compounds are aromatic. In vitro antioxidant screening of the compounds by DPPH free radical scavenging method showed that the compounds possessed significant antioxidant activity when compared with standards vitamin C, and butylatedhydroxylanisole (BHA). MB3 (73.56%, 71.17%), MB4 (78.83%, 75.25%), MB5 (73.06%, 70.58%), MB6 (74.55%, 72.47%) and MB8 (78.73%, 74.65%) showed significant inhibition at 1.0 mg/mL and 0.5 mg/mL respectively. MB1, MB2 and MB3 shows potent antimicrobial activity while MB4 – MB8 showed moderate activity, against bacterial and fungal strains when compared with the standards, Gentamicin and Tioconazole for bacteria and fungi respectively. This research work has therefore provided information about the spectroscopic properties, anti-oxidant and antimicrobial activities of new Mannich bases.