Anti-infective potential of hydroalcoholic extract of Punica granatum peel against gram-negative bacterial pathogens.

Chinmayi Joshi,Pooja Patel,Vijay Kothari

doi:10.12688/f1000research.17430.1

Abstract

Background: Punica granatum extracts have been prescribed in traditional medicine for management of a variety of disease conditions including microbial infections. Generation of scientific evidence for validation of P. granatum peel extract's anti-pathogenic efficacy is required. Methods: Hydroalcoholic extract of P. granatum peel (PGPE), prepared by microwave assisted extraction method was evaluated for its quorum-modulatory potential against two different human-pathogenic bacteria viz. Chromobacterium violaceum and Pseudomonas aeruginosa. Results: This extract was able to modulate in vitro production of quorum sensing-regulated pigments in both these test bacteria at ≥5 μg/ml. Virulence traits of P. aeruginosa like haemolytic activity, and biofilm formation were negatively affected by the test extract, and it also made P. aeruginosa more susceptible to lysis by human serum. Antibiotic susceptibility of both test bacteria was modulated owing to pre-treatment with PGPE. Exposure of these test pathogens to PGPE (≥0.5 μg/ml) effectively reduced their virulence towards the nematode Caenorhabditis elegans. Repeated subculturing of P. aeruginosa on PGPE-supplemented growth medium did not induce resistance to PGPE in this notorious pathogen, and this extract was also found to exert a post-extract effect on P. aeruginosa. Individual constituent phytocompounds of PGPE were found to be less efficacious than the whole extract. PGPE seemed to interfere with the signal-response machinery of P. aeruginosa and C. violaceum. PGPE also exhibited notable prebiotic potential by promoting growth of probiotic strains- Bifidobacterium bifidum and Lactobacillus plantarum at ≤50 μg/ml. Conclusions: This study indicates PGPE to be an effective antipathogenic and prebiotic preparation, and validates its therapeutic use mentioned in traditional medicine. This study also emphasizes the need for testing any bioactive extract at broadest possible concentration range, particularly in vivo, so that an accurate picture of dose-response relationship can emerge.

Highlights

Antimicrobial resistance (AMR) has been recognized as a global problem
C. violaceum C. violaceum was challenged with the P. granatum peel (PGPE) at 0.5–500 μg/ml (Figure 1A)
Production of the quorum sensing (QS)-regulated pigment violacein was sensitive to PGPE at lesser concentrations, and the inhibitory effect increased with increase in concentration of the extract

Summary

Introduction

Antimicrobial resistance (AMR) has been recognized as a global problem. Globalization and international travel has increased the vulnerability of any country to infections prevalent in other countries. Antimicrobial therapy has largely remained dependent on conventional bactericidal antibiotics Owing to their killing effect, such antibiotics pose considerably strong selection pressure on the pathogen populations to evolve resistant phenotypes. This necessitates thinking of alternative approaches for handling microbial infections, which asks for identifying novel targets, other than those (e.g. cell wall synthesis, nucleic acid/ protein synthesis, cell membrane) targeted by current antibiotics (Beceiro et al, 2013; Fair & Tor, 2014; Kohanski et al, 2010). Virulence traits of P. aeruginosa like haemolytic activity, and biofilm formation were negatively affected by the test extract, and it made P. aeruginosa more susceptible to lysis by human serum Antibiotic susceptibility of both test bacteria was modulated owing to pre-treatment with PGPE. This study emphasizes the need for testing any bioactive extract at broadest version 2

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