This study was undertaken to investigate the phytochemical and antibacterial activities of Vernonia amygdalina leaf extract against clinical isolates obtained from the University of Benin Teaching Hospital, using agar well diffusion method. Phytochemicals present in Vernonia amygdalin included flavonoids, cardiac glycosides, reducing sugar, terpenoids and saponins. Ethanolic extract acted against with inhibition zones ranging from 7.0±0.0mm at 25mg/ml to 14.5±2.5mm at 200mg/ml against E. coli; 6.5±0.5mm at 100mg/ml to 9.0±2.0mm at 200mg/ml against S. aureus; 11.0±1.0mm at 50mg/ml to 16.5±5.0mm at 200mg/ml; 7.5±1.5mm at 25mg/ml to 11.5±0.5mm at 200mg/ml. Inhibition zones in aqueous extract ranged from 8.0±2.0mm at 25mg/ml to 12.5±1.5 at 200mg/ml against P. aeruginosa; 9.0±1.0mm at 50mg/ml to 15.0±1.5mm at 200mg/ml against S aureus. The minimum inhibitory concentration of ethanolic extract ranged from 25mg/ml in S. aureus, P. aeruginosa, B. subtilis and K. pneumoniae to 50mg/ml in E. coli. Minimum bactericidal concentration of the ethanol extract was 50mg/ml in P. aeruginosa and K. pneumonia and 100mg/ml for E. coli, S. aureus and B. subtilis. MBC of 200mg/ml was observed for B. subtilis, S. aureus and P. aeruginosa in the aqueous fraction of the plant. The most antibiotic resistant bacterial strain was S. aureus (80%) while the least resistant was P. aeruginosa (10%). The most resistant bacterial strain was S. aureus (80%) while the least resistant was P. aeruginosa (10%). The most effective antibiotics were perfloxacin, ciprofloxacin, septrin and choramphenicol. Vernonia amygdalina extract was found to be more potent than conventional antibiotics.
The effect of pH on the antimicrobial activity of chitosans was evaluated with five different molecular weight chitosans (DMPAC: MW 152; DMPCA: MW 338; DPMCA(2): MW 418; DMCPA: MW550 and DCMPA,MW 558) at 500µg/ml concentration on different food-borne bacteria and fungi. Studies on pH was carried out at pH 3.0, 3.5, 4.0, 5.0 and 5.8 with 500µg/ml chitosan using an overnight broth of bacteria (0.05ml) sub-cultured in nutrient broth or MRS broth (for lactic acid bacteria). Fungi were incubated at 28+ 2 0 C for 72h and enumerated on sabouraud dextrose agar. The viable cell count of Staphylococcus aureus at pH 3.0 for all chitosans ranged between 1.23-1.76Log10CFU/ml while at pH 5.8 viable cell numbers was 2.38-5.26log10CFU/ml compared to the initial inoculum number of 7.06Log10CFU/ml. The growth of Listeria monocytogenes was totally suppressed by 500µg/ml chitosan at or below pH 5.0. Bacillus subtilis was susceptible to inhibition at low pH and had no detectable viable cell counts at pH 3.0-4.0. The viable cell numbers of Escherichia coli 0157:pH7 were reduced by approximately 2 log10 cycles at pH 5.8 and by more than 5 logs at pH3.0 with DMPAC chitosan. Rhizopus Stolonifer was reduced to non-detectable levels by DMPAC chitosan at pH 3-3.5.This mould was more sensitive to chitosan (500µg/ml) at all pH compared to Penicillium expansum and Aspergillu sniger. Saccharomyces cerevisiae and Pichia fermentans were similarly affected by low pH. The results of the present study show that application of chitosan to acidic foods such as fruit juices will enhance its effectiveness as a natural preservative.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.