Effect of Solvent Extraction and Blanching Pre-Treatment on Phytochemical, Antioxidant Properties, Enzyme Inactivation and Antibacterial Activities of ‘Wonderful’ Pomegranate Peel Extracts

Abstract

‘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 < 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.

Blanching Pre-Treatment Promotes High Yields, Bioactive Compounds, Antioxidants, Enzyme Inactivation and Antibacterial Activity of ‘Wonderful’ Pomegranate Peel Extracts at Three Different Harvest Maturities

“…The peels were blanched in a water bath (model 102, Scientific Engineering (Pty) Ltd., Maraisburg, South Africa) at 80 ± 2 • C for 3 min. This condition was based on a previous study from our laboratories [27]. Blanched peels were quickly soaked in cool water for 30 s to stop the blanching process and carefully drained.…”

“…We also hypothesized that blanching effect may vary according to the developmental stage (unripe, ripe, and over ripe) of pomegranate peel extracts and therefore affect the phytochemical profile of peel extracts positively at each developmental stage, which in turn will improve the bioactivity of the blanched peel extracts. Based on our previous study [27], we blanched at 80 • C for 3 min using 'Wonderful' at three harvest maturities, and with the aim of better defining the phytochemical effects of blanching, we determined the polyphenolic content and mapped their antioxidant potential using a variety of different in vitro spectrophotometric based assays to test this hypothesis. We further determined the enzyme activity of PPO and POD, and evaluated the effect of blanching on several commercially valuable compounds using a liquid chromatography mass spectrometry-based profiling technique.…”

Preparation and Characterization of Polycaprolactone (PCL) Antimicrobial Wound Dressing Loaded with Pomegranate Peel Extract

“…Nanofiber membranes are used as a carrier for the delivery of PPE. While polyphenols, being the major component of PPE, play a key role in antimicrobial and antioxidant activities . Therefore, the release of polyphenols is depicted as the release profile of PPE.…”

Fullerene Nanorings as Nitric Oxide Radical Scavengers for Ultraviolet-Induced Cellular Injury

“…Reactive nitrogen species (RNS), including nitric oxide radical (NO • ), produced by UV-irradiated human skin cells react with photo- or enzyme-catalyzation induced superoxide anion ( • O 2 – ) to generate peroxynitrite (ONOO – ), which would enhance oxidative damage and apoptosis of human skin cells. , Therefore, effective RNS scavenging is necessary for mitigating UV-induced skin damage. Though a variety of antioxidants, such as solubilized resveratrol, flavonoids, , betacyanins, and edaravone, have been reported in scavenging RNS, poor stability prevents their application for sustainable antioxidation, − which greatly reduces their usefulness as skin care products against UV radiation.…”

“…Fullerene (C 60 ) is known as a “free radical sponge” due to its carbon cage structure and a large number of p-π conjugated double bonds, − thus standing out among various antioxidants . Especially, C 60 possesses persistent radical scavenging ability, which benefits cytoprotection against cellular injury caused by free radicals. − Nevertheless, intrinsic C 60 is extremely hydrophobic, which limits its application in living organisms.…”