Characterization and antibacterial activity of tannin from selected food and agricultural wastes

Abstract

Tannins provide several advantages being as good biomaterial, antimicrobial, antioxidant, pharmaceutical, biopesticide, and nutraceutical agents. This study aimed to characterize tannin from three (3) agrowastes (Corn cob, cocoa pod, and coco peat) and compare their antimicrobial activity with that of synthetic tannin. The wastes were air-dried and blended. The tannin content was estimated using UV-Visible Spectrophotometric method. FTIR analysis of the samples was also carried out. Antimicrobial activity of different extracts of samples tannin and synthetic tannin on four (4) pathogenic bacteria (Salmonella Typhi, Bacillus subtilis, Staphylococcus aureus, and Klebsiella pnuemonae) was determined. Results obtained revealed the tannin content of samples in the order: coco peat (5.500 mg/g) >cocoa pod (4.740 mg/g) >corn cob (3.212 mg/g). The FTIR analysis showed a broad band at 3285-3216 cm^-1 for the three samples representing bonding –OH groups. The samples displayed peaks around 2928-2917cm^-1 representing aliphatic chains, -CH2- and –CH3. The peak around 1616-1576 cm^-1 corresponds to C-O vibrations. The peak around 1363-1256 cm^-1 corresponds to C (O)-O stretching vibrations and –OH in plane vibrations. These peaks correspond to peak values obtained from synthetic tannic acid. The four organisms were susceptible to aqueous extracts of tannin from all samples except Bacillus subtilis which was not susceptible to cocoa pod tannin. Salmonella typhi was not susceptible to synthetic tannin at all concentrations. Results from this study indicate that some agrowastes may be utilised as a source of cheap, readily available tannin and may also serve as a more effective antibacterial agent.