Evaluation of preservative properties and antimicrobial activities of Anogeissus leiocarpus extract on food pathogens of Hibiscus sabdariffacalyx (Zobo) drink

Abstract

The study was aimed at evaluating phytochemical constituents, antimicrobial and preservative activities of A. leiocarpus extract on zobo drink. The plant materials were sourced, identified and extracted using water and ethanol. Preliminary phytochemical screening of extracts and fractions was carried out using standard procedure. Isolation, identification of bacterial and fungal species commonly implicated in food borne illness and spoilage were carried out using standard protocol. Evaluation of antimicrobial and preservative activities of the extracts and fractions was also carried out. Result of phytochemical screening revealed the presence of saponnins, anthraquinones, alkaloids and tannins in aqueous and ethanol extracts of A. leiocarpus. Alkaloids and anthraquinones are present in all the fractions. The antimicrobial activities result showed ethanol extracts of A. leiocarpus possessed better antimicrobial activity among the extracts tested with zone diameter of 24.0±2.00mm at 2000μg/ml concentration against S. aureus. The activity of ethanol extract of A. leiocarpus at 2000μg/ml against E. coli, Salmonella spp and Shigella spp was 20.0+0.0mm, 13.5±0.50mm and 20.5±0.50mm. Antimicrobial activity of acetone fraction showed E. coli is sensitive (19.0±0.00mm) at 2000μg/ml but no significant difference (p<0.05) was observed when compared with other organisms. Treatments A, B, C and D showed significant decrease in Aerobic Bacteria Count by 0.62 log, 0.16 log, 0.77 log and 0.35 log after 48hrs of storage. Conclusively A. leiocarpus aqueous and ethanol extracts possess antimicrobial and preservative activities which should further be evaluated against different food systems.

Keywords: Phytochemicals, Antimicrobials, Fraction, Spoilage, Preservatives