A Comprehensive Study of the Antibacterial Activity of Bioactive Juice and Extracts from Pomegranate (Punica granatum L.) Peels and Seeds

Abstract

Due to the growing awareness of Punica granatum fruit’s health-promoting properties, the pomegranate is increasingly used for food purposes. This results in the formation of biological waste products such as peels. A biowaste circular bioeconomy strategy holds great prospective for a sustainable economy. Therefore, a sustainable and environmentally friendly way of disposing of waste (e.g., use of biowaste to obtain high-value components (e.g., punicalagins, enzymes)) is crucial for the protection of the environment and human health. In the presented study, the content of total phenols and proanthocyanidins in ten samples of Punica granatum fruit (juice, aqueous (H2O) and ethanolic (EtOH) extracts of peels and seeds) was determined. Peel extracts were found to be the richest in the content of secondary metabolites and showed extremely high antioxidant potential (approximately 90% inhibition: DPPH radical scavenging activity). To the best of our knowledge, this is the first comparative study to determine the enzymatic activity of α-amylase, lipase, peroxidase, protease, and transglutaminase in different P. granatum samples. Furthermore, the antibacterial efficacy of all P. granatum samples was qualitatively determined against three strains of Gram-negative (Escherichia coli, Pseudomonas aeruginosa, and Pseudomonas fluorescens) and three strains of Gram-positive (Bacillus cereus, Staphylococcus aureus, and Streptococcus pyogenes) bacteria, susceptible to gaining antibiotic resistance. Moreover, the most promising peel extracts were quantified for antibacterial efficacy against tested bacteria at five different concentrations. All samples slowed down and inhibited the growth of all tested bacteria. MIC90 values (2.7 or 0.3 mg/mL) were determined in 18 out of 24 experiments (four samples, six bacteria tested). There is no research in the reviewed literature that is current with such detailed and comprehensive determination of P. granatum peel extracts antibacterial activity. The results of the research showed great potential for the use of P. granatum in the field of antibacterial activity in biomedicine applications and in the cosmetic, food, and pharmaceutical industries.

Supercritical Fluid and Conventional Extractions of High Value-Added Compounds from Pomegranate Peels Waste: Production, Quantification and Antimicrobial Activity of Bioactive Constituents

“…There are no comparable results found in the literature for the quantitative determination of MGIR for SFE PP extracts, but the results are completely comparable with EtOH and H 2 O lyophilized PP extracts from Kupnik et al [ 30 ]. The only difference is that lower concentrations of EtOH and H 2 O extracts achieved higher MGIRs in the case of Gram-positive and Gram-negative bacteria, with the exception of H 2 O extract in the case of P. fluorescens , which inhibited the growth of this bacterium only at the highest concentration (2.7 mg/mL) of the extract.…”

“…However, it should be noted that the results of the studies may differ mainly due to divergent factors (e.g., variety types, climatic growing conditions, fruit ripeness, storage conditions, sample preparation, extraction method etc.) that may affect the content of bioactives and their properties [ 30 ].…”

“…All solvents except hexane gave extracts with the achieved antioxidant activity of above 90% inhibition. Furthermore, Kupnik et al [ 30 ] determined 90.05% inhibition of EtOH PP extract obtained by SE, while Sharayei et al [ 32 ] performed UE for extracting effective compounds from PP. Samples exhibited 15.85–88.76% antioxidative activity, using DPPH assay.…”

“…Based on the reviewed literature, we did not find a comparable study covering the antimicrobial activity of SFE PP extracts. However, for ease of illustration, a recent study by Kupnik et al [ 30 ] demonstrated the antibacterial activity of EtOH PP extract (Soxhlet extraction) and H 2 O PP extract (Homogenizer-assisted extraction). EtOH extract of lyophilized PP was found to inhibit the growth of Gram-negative bacteria with the inhibition zones in the range 17–23 ± 2 mm and the growth of Gram-positive bacteria with 11–23 ± 2 mm.…”

“…For qualitative analysis of the antimicrobial activity of the analyzed sample disc, the diffusion method (DDM) was used [ 30 , 43 ]. The concentration of microorganisms was 1–5 × 10 6 CFU/mL.…”