Analysis of Total Phenolic Content and Antibacterial Activity of Black Pomegranate (Punica granatumL.) Peel: Potential as a Natural AntibacterialAgent

Pomegranate peel is food waste unfit to eat parts obtained during the production of pomegranate juice. The aim of this work is to study the effect of four different solvents (ethanol, isopropanol, hot and cold water) on phytochemicals screening, total phenolics content, total flavonoid content and antioxidants activity in pomegranate peels, as well as identification of phenolic compounds in extracts by HPLC. Phenolics, flavonoids, alkaloids, saponins, tannins, steroids and terpenoids were detected in all extracts. The highest total phenolics and total flavonoids were observed in ethanol extract of pomegranate peels (161.5 mg GAE/g and 70.65 mg Rutin/g), respectively. Furthermore, the ethanol extract of pomegranate peels showed the highest DPPH scavenging activity with the lowest IC50 value 14.6 μg/ml compared to other extracts. The high antioxidant activities may be due to the high contents of phenolics and flavonoids in pomegranate peel ethanol extract. HPLC analysis was used for the identification and quantitative determination of phenolic compounds in pomegranate peels extracts. The results revealed nine polyphenolic compounds including protocatechuic acid, p-coumaric acid, caffeic acid, ellagic acid, cinnamic acid, quinic acid, benzoic acid, syringic acid and iso-ferulic acid in pomegranate peels extracts. The obtained results confirmed that ethanol extract was the most abundant of phenolics compounds as compared to the other extracts. Finally, it can be concluded that pomegranate peel extracts can be used in various fields for being rich in natural antioxidants that have a medicinal and therapeutic impact.

Utilizing pomegranate extracts for enhancing yogurt quality and preservation

The hawthorn Crataegus mexicana is a traditional Mexican fruit with properties that make this fruit useful for the treatment of many ailments, including diseases of the respiratory and urinary tract. This paper reports the antioxidant capacity of the n-hexane, dichloromethane, ethyl acetate, acetone, ethanol and methanol extracts of C. mexicana. Samples were evaluated for total phenolic and carotenoid contents, 2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical scavenging, the inhibition of the formation of thiobarbituric acid reactive species (TBARS) and the neutralization of the cation-radical 2,2´-azino-bis(3ethyl benzothiazoline-6-sulfonic acid) diammonium salt (ABTS). The total phenolic content was 2.65 ± 0.23 mg of gallic acid equivalents per gram, and the carotenoid content was 26.4 ± 0.02 µg/g in dry hawthorn skin. The most active extract in scavenging DPPH radicals and inhibiting TBARS formation was the acetone extract, with activities of 21.9 ± 0.15 and 13.27 ± 0.70%, respectively, at 10 mg/L. The extracts were compared for activity against ascorbic acid, caffeic acid, α- tocopherol and quercetin. The acetone extract was the most active, with an IC50 value of 15.2 mg/L in DPPH and 17.7 mg/L in TBARS. A high correlation was observed between the results for TBARS and DPPH. These results demonstrate the potential nutritional and antioxidant value of this Mexican fruit.

Introduction and Aim: Citrus fruits are rich in polyphenolic compounds. The conventional medical system has utilized the fruit’s entire composition including the peel for its diverse biological functions. With this, the study aimed to assess and compare the phytochemical, in-vitro antioxidant analysis as well as polyphenol and flavonoid content of Citrus maxima juice, aqueous and ethanolic extracts of its pulp and peel. Materials and Methods: Qualitative phytochemical screening, total phenolic content and total flavonoid content and different in-vitro antioxidant assays like total antioxidant capacity (TAC), Ferric reducing antioxidant power assay (FRAP), 2,2-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging assay were carried out to evaluate the in-vitro antioxidant potential in the juice, aqueous and ethanolic extract of pulp and peel of C. maxima. Gas chromatography–Mass spectrometry (GC–MS) analysis was performed in the peel ethanolic extract to identify the compounds present. Results: Preliminary phytochemical analysis revealed the presence of triterpenoids and steroids, glycosides, alkaloids, flavonoids, carbohydrates and vitamin C in all the C. maxima crude extracts. Tannins were present only in pulp of ethanol extract and in both aqueous and ethanol extracts of peel. Resins were present in the juice and ethanol extract of pulp and peel. The total phenol and total flavonoid content was comparatively higher in ethanolic extracts of peel. All the extracts showed dose-dependent free radical scavenging activity. The reducing potential of the C.maxima extractives increased with the increase in its concentration. GC-MS analysis of ethanolic peel extract identified key constituents with pharmacological effects. The ethanolic peel extract showed good antioxidant activity and free radical scavenging activity when compared to other extracts. Conclusion: The results indicated that ethanolic peel extract of Citrus maxima revealed the highest presence of polyphenolic compounds, which are secondary plant metabolites with potential antioxidant activity.

The current study focuses on Punica granatum L. (pomegranate) peel and peel extract and their use as functional foods, food additives, or physiologically active constituents in nutraceutical formulations. The pomegranate peel extract is a good source of bioactive substances needed for the biological activity of the fruit, including phenolic acids, minerals, flavonoids (anthocyanins), and hydrolyzable tannins (gallic acid). The macromolecules found in pomegranate peel and peel extract have been recommended as substitutes for synthetic nutraceuticals, food additives, and chemo‐preventive agents because of their well‐known ethno‐medical significance and chemical properties. Moreover, considering the promises for both their health‐promoting activities and chemical properties, the dietary and nutraceutical significance of pomegranate peel and pomegranate peel extract appears to be underestimated. The present review article details their nutritional composition, phytochemical profile, food applications, nutraceutical action, and health benefits.

BackgroundThe use of pomegranate peel is highly associated with its rich phenolic concentration. Series of drying methods are recommended since bioactive compounds are highly sensitive to thermal degradation. The study was conducted to evaluate the effects of drying on the bioactive compounds, antioxidant as well as antibacterial and antityrosinase activities of pomegranate peel.MethodsDried pomegranate peels with the initial moisture content of 70.30 % wet basis were prepared by freeze and oven drying at 40, 50 and 60 °C. Difference in CIE-LAB, chroma (C*) and hue angle (h°) were determined using colorimeter. Individual polyphenol retention was determined using LC-MS and LC-MSE while total phenolics concentration (TPC), total flavonoid concentration (TFC), total tannins concentration (TTC) and vitamin C concentration were measured using colorimetric methods. The antioxidant activity was measured by radical scavenging activity (RSA) and ferric reducing antioxidant power (FRAP). Furthermore, the antibacterial activity of methanolic peel extracts were tested on Gram negative (Escherichia coli and Klebsiella pneumonia) and Gram positive bacteria (Staphylococcus aureus and Bacillus subtilis) using the in vitro microdilution assays. Tyrosinase enzyme inhibition was investigated against monophenolase (tyrosine) and diphenolase (DOPA), with arbutin as positive controls.ResultsOven drying at 60 °C resulted in high punicalin concentration (888.04 ± 141.03 mg CE/kg dried matter) along with poor red coloration (high hue angle). Freeze dried peel contained higher catechin concentration (674.51 mg/kg drying matter) + catechin and –epicatechin (70.56 mg/kg drying matter) compared to oven dried peel. Furthermore, freeze dried peel had the highest total phenolic, tannin and flavonoid concentrations compared to oven dried peel over the temperature range studied. High concentration of vitamin C (31.19 μg AAE/g dried matter) was observed in the oven dried (40 °C) pomegranate peel. Drying at 50 °C showed the highest inhibitory activity with the MIC values of 0.10 mg/ml against Gram positive (Staphylococcus aureus and Bacillus subtili. Likewise, the extracts dried at 50 °C showed potent inhibitory activity concentration (22.95 mg/ml) against monophenolase. Principal component analysis showed that the peel colour characteristics and bioactive compounds isolated the investigated drying method.ConclusionsThe freeze and oven dried peel extracts exhibited a significant antibacterial and antioxidant activities. The freeze drying method had higher total phenolic, tannin and flavonoid concentration therefore can be explored as a feasible method for processing pomegranate peel to ensure retention of the maximum amount of their naturally occurring bioactive compounds.Trial registrationNot relevant for this study.

Fenpropathrin (FNP) is one of the commonly used insecticides in agriculture and domestically, leading to environmental and health problems. The goal of the current investigation was to determine how well pomegranate peel extract (PGPE) could prevent the testicular toxicity and oxidative stress induced by FNP. Four groups of male Wistar rats were randomly assigned: negative control (corn oil), PGPE (500 mg/kg BW), positive control (FNP; 15 mg/kg BW, 1/15 LD50), and PGPE + FNP. For four weeks, the rats received their doses daily and orally via gavage. The major phytochemical components (total phenolic, flavonoids, and tannins contents) detected in PGPE by GC-MS included ellagic acid, hydroxymethylfurfurole, guanosine, and pyrogallol with high total phenolic, flavonoids, and tannin contents. FNP-treated rats showed a marked elevation in testicular levels of thiobarbituric acid-reactive substances, hydrogen peroxide, and protein carbonyl content, as well as the activity of aminotransferases and phosphatases. Meanwhile. a significant decline in body weight, gonadosomatic index, glutathione, protein contents, enzymatic antioxidants, and hydroxysteroid dehydrogenase (3β HSD, and 17β HSD) activity was observed. In addition, significant alterations in testicular P53, Cas-3, Bcl-2, IL-β, IL-10, testosterone, follicle-stimulating and luteinizing hormones, and sperm quality were detected. Furthermore, biochemical and molecular changes were corroborated testicular histological abnormalities. Moreover, PGPE-pretreated FNP-intoxicated rats demonstrated considerable improvement in the majority of the studied parameters, when compared to FNP-treated groups. Conclusively, PGPE provided a potent protective effect against the testicular toxicity caused by FNP, due to its antioxidant-active components.

Evaluation of antioxidant properties of pomegranate peel extract in comparison with pomegranate pulp extract

Background: Denture stomatitis, caused primarily by Candida albicans overgrowth, is a common oral health issue among denture wearers. Maintaining denture hygiene is crucial for prevention. This study investigated the efficacy of red pomegranate (Punica granatum L.) peel and fruit extracts as natural denture cleansers compared to sodium bicarbonate, a standard denture cleansing agent. Methods: Heat-cured acrylic resin plates were fabricated and contaminated with C. albicans. Samples were divided into four groups and soaked for 8 hours in: 75% pomegranate peel extract, 75% pomegranate fruit extract, 5% sodium bicarbonate solution (positive control), and aquadest (negative control). C. albicans colony counts were performed using the spread plate technique and colony counter. Data were analyzed using Kruskal-Wallis and Mann-Whitney tests. Results: Both pomegranate peel and fruit extracts significantly reduced C. albicans growth compared to the negative control (p<0.05). The peel extract showed comparable efficacy to sodium bicarbonate (p>0.05), while the fruit extract demonstrated slightly lower but still substantial antifungal activity. Conclusion: Red pomegranate peel and fruit extracts hold promise as natural denture cleansers for inhibiting C. albicans and potentially preventing denture stomatitis. Further research is warranted to evaluate their long-term effects on denture materials and clinical efficacy.

Pomegranate peels, the main byproduct of pomegranate production, are rich in phenolic compounds that are known for their effective antioxidant properties and have vast application prospects. In this study, steam explosion, an environmentally friendly technique, was applied to pretreat pomegranate peels for phenol extraction. We investigated the effects of explosion pressure, duration, and particle size on the content of total and individual phenolics, and antioxidant activity of pomegranate peels before and after in vitro digestion. The optimal conditions for a steam explosion for pomegranate peels in terms of total phenol content were a pressure of 1.5 MPa, a maintenance time of 90 s, and a particle size of 40 mesh. Under these conditions, pomegranate peel extract presented a higher yield of total phenols, gallic acid, and ellagic acid. However, it also had a lower content of punicalin and punicalagin, compared to the unexploded peels. There was no improvement in the antioxidant activity of pomegranate peels after the steam explosion. Moreover, the content of total phenol, gallic acid, ellagic acid, punicalin, and punicalagin, as well as the antioxidant activity of pomegranate peels, all increased after gastric digestion. Nevertheless, there was a large variation in the pomegranate peel processed by different pressure, duration, and sieve fractions. Overall, this study demonstrated that steam explosion pre-treatment could be an efficient method for improving the release of phenolics, especially gallic acid, and ellagic acid, from pomegranate peels.

The encapsulation of pomegranate peel extract (PPE) in chitosan nanoparticles (CSNPs) is an advantageous strategy to protect sensitive constituents of the extract. This study was aimed to develop PPE-loaded CSNPs and characterize their physical, structural morphology, antioxidant and antimicrobial properties. Spherical NPs were successfully synthesized with a mean diameter of 174–898 nm, a zeta potential (ZP) of +3 – +36 mV, an encapsulation efficiency (EE) of 26–70%, and a loading capacity (LC) of 14–21% depending on their loaded extract concentrations. Based on these results, CSNPs with chitosan:PPE ratio of 1:0.50 (w/w) exhibited good physical stability (ZP = 27 mV), the highest loading (LC = 20%) and desirable encapsulation efficiency (EE = 51%), and thus, selected as optimally loaded NPs. The FTIR analysis of PPE-CSNPs demonstrated no spectral changes indicating no possible chemical interaction between the PPE and CSNPs, which confirms that the PPE was physically entrapped within NPs. Moreover, FTIR spectra of pure PPE showed specific absorption bands (at 3293–3450 cm−1) attributed to the incidence of phenolic compounds, such as tannic acid, ellagic acid and gallic acid. Total phenolic content (TPC) and antioxidant analysis of selected CSNPs revealed that the encapsulated NPs had significantly lower TPC and antioxidant activity than those of pure PPE, indicating that CSNPs successfully preserved PPE from rapid release during the measurements. Antibacterial tests indicated that pure PPE and PPE-loaded CSNPs effectively retarded the growth of Gram-positive S. aureus with a minimum inhibitory concentration (MIC) of 0.27 and 1.1 mg/mL, respectively. Whereas Gram-negative E. coli, due to its protective cell membrane, was not retarded by pure PPE and PPE-CSNPs at the MIC values tested in this study. Gas chromatography-mass spectroscopy analysis confirmed the incidence of various phytochemicals, including phenolic compounds, fatty acids, and furfurals, with possible antioxidant or antimicrobial properties. Overall, CSNPs can be regarded as suitable nanomaterials for the protection and controlled delivery of natural antioxidants/antimicrobials, such as PPE in food packaging applications.

‘Wonderful’ pomegranate (Punica granatum L.) peel contains a wide range of phytochemicals including vitamins, dietary fibre, phenolic compounds, and antioxidant properties. Yet, it is often used as animal feed or discarded in landfills, which is not the best eco-friendly way to utilize this phenolic-rich bioresource. Finding novel ways of utilizing pomegranate peel waste could prove a more profitable and eco-friendlier alternative that is far more beneficial to the economy. Adding a blanching pre-treatment step at optimal conditions prior to processing of pomegranate peel aids in the inactivation of quality changing enzymes such as polyphenol oxidase (PPO) and peroxidase (POD), which are accountable for the degradation reactions that cause breakdown of nutrients and phytochemicals. This study aimed to determine the effect of blanching at 80 °C for 3 min on the yield, polyphenol content, antioxidant properties, enzyme inactivation, and antibacterial activity of ‘Wonderful’ pomegranate peel ethanolic extracts from three different harvest maturities (unripe, ripe, and over ripe), including a comprehensive characterization and quantification using liquid chromatography-mass spectrometry (LC-MS). The blanched unripe peel extracts exhibited the highest total phenolic content, total tannin content, 2,2-diphenyl-1-picryl hydrazyl (DPPH) antioxidant activity, 2,2-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid (ABTS) radical scavenging activity and ferric ion reducing antioxidant power (FRAP) at 14.0 mg gallic acid equivalent (GAE)/g dry mass (DM), 1.0 mg GAE/g DM, 359.1 µmol Trolox/g DM, 912.2 µmol Trolox/g DM and 802.5 µmol Trolox/g DM, respectively. There was significant (p < 0.05) decrease in PPO and POD activity of all blanched pomegranate peel extracts. The blanched unripe peel extracts had the lowest PPO activity at 0.2 U/g fresh weight (FW), with a 70% PPO inactivation compared to ripe and over ripe harvest, whereas the highest POD inactivation was recorded at 67% in over ripe peel extracts. All blanched peel extracts, irrespective of harvest maturity, had minimum inhibitory concentration (MIC) values at 160 µg/mL against all four bacteria strains tested, which included two Gram-positive bacterial strains (Bacillus subtilis ATCC 6051 and Staphylococcus aureus ATCC 12600) and two Gram-negative bacteria (Escherichia coli 11775 and Klebsiella pneumonia ATCC 13883). A total of 25 metabolites including phenolic acids (4), organic acids (1), flavonoids (4), ellagitannins (13), and other polyphenols (3) in all three pomegranate peel samples were tentatively identified after LC-MS profiling. The blanched unripe peel extracts showed significantly higher punicalin α and β, β punicalagin, catechin, epicatechin content at 414 mg/g, and 678 mg/g, 151 mg/g, 229 mg/g, respectively, compared to peel extracts from other harvest maturities. This study provides supportive information for the commercial utilization of pomegranate fruit peel as source of value-added ingredients for the development of novel food, cosmetics, and pharmacological products.

‘Wonderful’ pomegranate (Punica granatum L.) peel is rich in phytochemicals which are responsible for its strong antioxidant and antimicrobial activities, but it has low economic value as it is mainly discarded, causing an environmental waste management problem. To examine the best processing regime for pomegranate peel wastes, different solvents (ethanol, methanol and acetone) at various concentrations (50%, 70% and 100%) and blanching at 60, 80 and 100 °C for 1, 3 and 5 min, for each temperature, were tested. Ethanol at 70% (v/v) provided the highest extract yield, total phenolic and total tannin content at 29.46%, 10.61 ± 0.15, and 0.76 ± 0.02 mg GAE/g DM, respectively. Antioxidant activity using the 2,2 diphenyl-1-picryl hydrazyl assay (DPPH), ferric-reducing antioxidant power assay (FRAP) and 2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid assay (ABTS) were reported at 243.97 ± 2.43, 478.04 ± 73.98 and 718.79 ± 2.42 µmol Trolox/g DM, respectively. A blanching temperature of 80 °C for 3 min led to the highest extract that had a total phenolic content of 12.22 ± 0.08 mg GAE/g DM and total tannin content of 1.06 ± 0.06 mg GAE/g DM. This extract also exhibited the best antioxidant activity for the DPPH, FRAP and ABTS assays. Two blanching temperatures, 80 or 100 °C, significantly reduced polyphenol oxidase and peroxidase activities (p &lt; 0.05). Although blanched peel extracts showed a broad-spectrum activity against test bacteria, blanching at 80 °C for 3 or 5 min was most effective. Hot water blanching is thus a suitable environmentally friendly post-harvesting processing method for pomegranate peels that are intended for use as extracts in value-added products with good antioxidant and antibacterial effects.

The aim of this study is to determine and compare the antioxidant and antiproliferative activities of juices and extracts of the peel, aril and membrane of the cultivated and wild pomegranate fruits. The content of total phenols, total flavonoids, total flavonols, total flavan-3-ols and total anthocyanins was determined spectrophotometrically. The individual phenolics were quantified by HPLC. Antioxidant activity was determined by DPPH and ABTS tests and neutralisation of hydroxyl radical, while the antiproliferative activity was measured in vitro by sulforhodamine B (SRB) assay. Total phenolics were statistically highest in wild pomegranate peel extract, expressed in gallic acid equivalents, 340.92 mg/g (p<0.05), while total flavonoid content was the highest in cultivated pomegranate peel extract, expressed in quercetin equivalents, 31.84 mg/g (p<0.05). The sample of wild pomegranate peel extract showed the highest antioxidant activity with respect to free DPPH and ABTS radicals. The samples of cultivated pomegranate peel and membrane extracts had almost identical and the strongest effect on the inhibition of hydroxyl radicals (41.24 and 41.23 μg/mL, respectively). The sample of wild pomegranate peel extract showed the strongest effect on the growth inhibition of all tested tumour cell lines. In this study, the bioactivity of different parts of cultivated and wild pomegranates was determined and compared. In the available literature, the individual antioxidant and antiproliferative activity of only some parts of the pomegranate fruit was investigated. All parts of the pomegranate fruit were investigated, including the membrane, which was barely analysed in other works. The wild pomegranate has also been less analysed in previous studies. Future research should focus on in vivo studies of the obtained pomegranate samples.

ABSTRACTThis study investigated the effect of dietary α-tocopherol (α-Toc), pomegranate peel extract (PPE), and pomegranate peel (PP) on phenolic content and breast meat quality of broilers during 11 days of storage with the addition of α-Toc, PPE, and PP. Broilers were fed eight dietary treatments, including: control diet, α-Toc diet (200 mg/kg), PPE diets (100, 200, and 300 mg/kg), and PP diets (1, 2, and 3 g/kg) during 0–42 days. The extents of lipid oxidation in samples were assessed by measuring thiobarbituric acid-reactive substances and the 1, 1-Diphenyl-2-picrylhydrazyl radical-scavenging activities were determined. The feed efficiency was improved significantly in chickens fed diet containing 0.2 g/kg PPE, and the growth performance of chickens was impaired in chickens fed with PP diet. Long-chain polyunsaturated fatty acids n-3 were increased in breast muscles of broilers fed α-Toc and high levels of PPE diets (P < .05). Total phenolic contents and antioxidant activity in the breast meat were improved significantly when chickens fed diets containing α-Toc and PPE (P < .05). In conclusion, dietary supplementation with 200 and 300 mg/kg PPE may improve the antioxidant potential and quality indices of broilers breast meat. The antioxidant potential of PPE was equal to that of α-Toc in refrigerated meat.