Context: The global surge in multi-drug resistant bacteria and the imminence of tuberculosis pandemic necessitate alternative therapeutic approaches to augment the existing medications. Pomegranate, the fruit of Punica granatum Linn. (Punicaceae), widely recognized for potency against a broad spectrum of bacterial pathogens, deserves further investigation in this respect.
Objective: This study determines the therapeutic potential of pomegranate juice, extracts of non-edible peel prepared with methanol/water, and its four polyphenolic constituents, namely caffeic acid, ellagic acid, epigallocatechin-3-gallate (EGCG) and quercetin, against drug-resistant clinical isolates.
Materials and methods: Phenotypic characterisation of Mycobacterium tuberculosis, extended-spectrum β-lactamase (ESBL) and KPC-type carbapenemase producing Klebsiella pneumoniae was performed by biochemical and molecular methods. Resistance profiles of M. tuberculosis and K. pneumoniae were determined using LJ proportion and Kirby-Bauer methods, respectively. Pomegranate fruit extracts, and the compounds, were evaluated at a dose range of 1024-0.5 µg/mL, and 512-0.25 µg/mL, respectively, to determine minimum inhibitory (MIC) and bactericidal concentrations (MBC) against the drug-resistant isolates by the broth micro-dilution method.
Results: The peel extracts exhibited greater antimycobacterial activity (MIC 64-1024 μg/mL) than the potable juice (MIC 256 - > 1024 μg/mL). EGCG and quercetin exhibited higher antitubercular (MIC 32-256 μg/mL) and antibacterial (MIC 64-56 μg/mL) potencies than caffeic acid and ellagic acid (MIC 64-512 μg/mL).
Discussion and conclusion: The pomegranate fruit peel and pure constituents were active against a broad panel of M. tuberculosis and β-lactamase producing K. pneumoniae isolates. EGCG and quercetin need further investigation for prospective application against respiratory infections.
Keywords: Antitubercular; Punica granatum Linn.; caffeic acid; carbapenemase; ellagic acid; epigallocatechin-3-gallate; extended-spectrum β-lactamase; quercetin.