Phytochemical Composition, Antioxidant and Antibacterial Properties of Pummelo (Citrus maxima (Burm.)) Merr. against Escherichia coli and Salmonella typhimurium

The antioxidant and antibacterial activities of the phytochemical constituents of the pericarp, mesocarp and segment membrane crude ethanolic extracts of Pummelo (Citrus maxima (Burm.)) fruit were were tested against Escherichia coli and Salmonella typhimurium. Preliminary phytochemical test revealed the presence of phenols, tannins, saponins expressed as catechine quivalent (CE)/100ml and flavonoid expressed as gallic acid equivalent (GAE)/100ml. The order of which was as follows pericarp > segment membrane > mesocarp. The strongest antioxidant activity was obtained by the pericarp extract (29.64 expressed as % lipid peroxidation). The differences in the measured amount of phytochemicals and antioxidant activity among the three sample extracts were found to be significant. In terms of antimicrobial activity, the pericarp, mesocarp and segment membrane extracts generated zone of inhibitions measuring 17.10, 18.00 and 17.03 mm for S. typhimurium, respectively at 100% concentration. E. coli was noted to be inactive in all three sample extracts at 100% concentration. The capacity of E. coli to counteract the inhibitory effect of the phytochemicals contained in the pummelo extracts may be attributed to its rough corrugated cell wall and thick periplasmic space as opposed to the smooth curved and barely seen periplasmic space of S. typhimurium. However, no significant correlation was detected among the phytochemical content, antioxidant and in vitro antimicrobial activities of the sample extracts against S. typhimurium.