Antioxidant Rich Extracts of Terminalia ferdinandiana Inhibit the Growth of Foodborne Bacteria

Abstract

Terminalia ferdinandiana (Kakadu plum) is a native Australian plant containing phytochemicals with antioxidant capacity. In the search for alternatives to synthetic preservatives, antioxidants from plants and herbs are increasingly being investigated for the preservation of food. In this study, extracts were prepared from Terminalia ferdinandiana fruit, leaves, seedcoats, and bark using different solvents. Hydrolysable and condensed tannin contents in the extracts were determined, as well as antioxidant capacity, by measuring the total phenolic content (TPC) and free radical scavenging activity using the 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assay. Total phenolic content was higher in the fruits and barks with methanol extracts, containing the highest TPC, hydrolysable tannins, and DPPH-free radical scavenging capacity (12.2 ± 2.8 g/100 g dry weight (DW), 55 ± 2 mg/100 g DW, and 93% respectively). Saponins and condensed tannins were highest in bark extracts (7.0 ± 0.2 and 6.5 ± 0.7 g/100 g DW). The antimicrobial activity of extracts from fruit and leaves showed larger zones of inhibition, compared to seedcoats and barks, against the foodborne bacteria Listeria monocytogenes, Bacillus cereus, Methicillin resistant Staphylococcus aureus, and clinical isolates of Pseudomonas aeruginosa. The minimum inhibitory concentration and minimum bactericidal concentration in response to the different extracts ranged from 1.0 to 3.0 mg/mL. Scanning electron microscopy images of the treated bacteria showed morphological changes, leading to cell death. These results suggest that antioxidant rich extracts of Terminalia ferdinandiana fruits and leaves have potential applications as natural antimicrobials in food preservation.

Review on Natural Preservatives for Extending Fish Shelf Life

“…Plant extracts have broad application prospects in fish preservation. The antimicrobial activities of plant extracts may be attributed to the combined effects of polyphenols adsorption to bacterial membrane with membrane disruption and subsequent cellular contents leakage, and the generation of hydroperoxides from polyphenols [111,112,113,114]. Plant extracts also show antifungal activities, antioxidant, antimutagenic activities, and inhibit lipid oxidation in food [115,116,117,118].…”

Plants of the Genus Terminalia: An Insight on Its Biological Potentials, Pre-Clinical and Clinical Studies

“…extracts. The report by Akter et al. (2019) , evaluates the antimicrobial capacity of Terminalia ferdinandiana Exell.…”

“…extracts; on this subject, ethanol and acetone extracts showed the most potent antibacterial inhibitory activity. The authors argue that intriguingly, the extracts with the highest antioxidant activity (methanol and water extracts) were not the ones with the highest antibacterial activity, which may indicate that the compounds that may be differentially found in each type of extracts ( Akter et al., 2019 ).…”

“…& Diels bark extract inhibited diarrhea-causing pathogens including Shigella dysenteriae and Salmonella typhi ( Kuete et al., 2010 ). The bark, fruit, and seed coat extracts of Terminalia ferdinandiana Exell inhibited Bacillus cereus and methicillin-resistant Staphylococcus aureus with inhibition zone ranging from 7–17.8 mm ( Akter et al., 2019 ). Moreover, the extracts of Terminalia sp.…”

Introduction to the Special Issue: Foods of Plant Origin

“…Akter et al [2] studied the antimicrobial activity of Terminalia Ferdinandiana (Kakadu plum), a native Australian fruit rich in antioxidants. The presented results clearly demonstrated a strong antimicrobial activity of Terminalia ferdinandiana fruit and leaf extracts, and potential applications as natural antimicrobials in food preservation.…”