Abstract
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.
Highlights
The food industry produces copious amounts of agricultural waste with potential application as the substrate for the recovery of added-value compounds [1,2]
loading capacity (LC) and mean diameter (MD) variables with R2 values of 0.57 and 0.56, respectively showed less significant correlations at p = 0.013 and p = 0.0044, respectively compared to those of aforementioned variables. These results indicate that encapsulation efficiency and zeta potential are highly and negatively dependent on pomegranate peel extract (PPE) concentration in chitosan nanoparticles
It has to be mentioned that pure PPE was used at a concentration equal to that of loaded in chitosan nanoparticles (CSNPs) at a CS:PPE ratio of 1:0.50
Summary
The food industry produces copious amounts of agricultural waste with potential application as the substrate for the recovery of added-value compounds [1,2]. Nanomaterials 2021, 11, 1439 from plant byproducts, with potent use in food preservation [3], agricultural [4], pharmaceutical [5] and cosmetics [6]. The peels are rich in bioactive compounds, such as polyphenols, flavonoids, proanthocyanidins, and hydrolyzable tannins compared to pomegranate juice and seeds [7,8,9,10]. It is reported that pomegranate peels possess strong antioxidant [11], antimicrobial [5,12], antiviral [13], anti-inflammatory [14], antimutagenic [15], and anticarcinogenic activities [16]. The antioxidant activity of pomegranate pericarp is due to its polyphenolic constituents (mostly punicalagin and ellagic acid), which, even at small concentrations, can inhibit oxidation processes and provide positive effects in the human body [8]
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