Technologies and extraction methods of polyphenolic compounds derived from pomegranate (Punica granatum) peels. a mini review

The interest in using plant by-product extracts as functional ingredients is continuously rising due to environmental and financial prospects. The development of new technologies has led to the achievement of aqueous extracts with high bioactivity that is preferable due to organic solvents nonuse. Recently, widely applied and emerging technologies, such as Simple Stirring, Pressure-Applied Extraction, Enzymatic Extraction, Ultrasound-Assisted Extraction, Pulsed Electric Fields, High Hydrostatic Pressure, Ohmic Heating, Microwave Assistant Extraction and the use of “green” solvents such as the deep eutectic solvents, have been investigated in order to contribute to the minimization of disadvantages on the extraction of bioactive compounds. This review is focused on bioactive compounds derived from pomegranate (Punica granatum) peels and highlighted the most attractive extraction methods. It is believed that these findings could be a useful tool for the pomegranate juices industry to apply an effective and economically viable extraction process, transforming a by-product to a high added value functional product. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Optimization of vacuum microwave-assisted extraction of pomegranate fruits peels by the evaluation of extracts’ phenolic content and antioxidant activity

The global interest in the use of plant by-product extracts as functional ingredients is continuously rising due to environmental, financial and health benefits. The latest advances in extraction technology have led to the production of aqueous extracts with high bioactive properties, which do not require the use of organic solvents. The purpose of this study was to optimize the conditions applied for the extraction of pomegranate peels (PP) via a “green” industrial type of vacuum microwave-assisted aqueous extraction (VMAAE), by assessing the potential bioactivity of the extracts (in terms of phenolic content and antioxidant activity), using a response surface methodology. The extraction conditions of temperature, microwave power, time and water/PP ratio were determined by the response surface methodology, in order to yield extracts with optimal total phenolics concentrations (TPC) and high antioxidant activity, based on the IC50 value of the scavenging of the 2,2-diphenyl-1-picrylhydrazyl (DPPH•) radical. The values of the optimum extraction parameters, such as extraction temperature (61.48 and 79.158◦C), time (10 and 12.17 min), microwave power (3797.24 and 3576.47 W) and ratio of water to raw material (39.92% and 38.2%), were estimated statistically for the two responses (TPC and IC50 values), respectively. Under these optimal extraction conditions, PP extracts with high TPC ((5.542 mg Gallic Acid Equivalent (GAE)/g fresh PP))/min and radical scavenging activity (100 mg/L (1.6 L/min)) could be obtained. Our results highlighted that the optimized industrial type of VMAAE could be a promising solution for the valorization of the PP by-products. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Effectiveness of olive fruit polyphenol extract combined with aqueous extracts of solid wastes of pomegranate or/ and orange juice against important plant pathogens - Part 2 (in vivo studies)

Olive fruit extracts, combined with pomegranate and orange waste extracts, isolated using microwave assisted extraction technique, were used as a potential alternative crop protection method against Verticillium dahliae, Rhizoctonia solani, Botrytis cinerea and Pyrenochaeta lycopersici on tomato plants. For the evaluation of the antimicrobial activity, various mixtures of the extracts were applied on 15 days old tomato plants, variety “Bella Dona”, infected by the above-mentioned pathogens. After 40 days of treatments, plant growth parameters such as plant fresh and dry weight, root weight, plant height, number of blossoms and number of formed fruits were calculated in order to assess the extract effectiveness. The results indicated that the four pathogens dramatically reduced tomato growth. In contrast, most of the evaluated extracts provided satisfactory control of the pathogens resulting in tomato growth similar to that of the uninfected control plants. Conclusively, the use of these polyphenolic extracts could protect tomato plants in case of fungal infection. Copyright © 2021 by authors, all rights reserved. Authors agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International Licens

Corn silage supplemented with pomegranate (Punica granatum) and avocado (persea americana) pulp and seed wastes for improvement of meat characteristics in poultry production

In the present study, pomegranate peels, avocado peels, and seed vacuum microwave extraction solid by-products were supplemented in corn silage in order to investigate the effects on meat quality and growth rate in broiler chicken. There were 50 broilers, divided in two groups, treated with experimental or usual feed for 43 days (group A: 25 broilers fed with avocado and pomegranate by-products and group B: 25 broilers fed with corn-silage used as control). The results showed that broiler chickens fed with a diet supplemented with a mixture of pomegranate avocado by-products (group A) showed significant differences in chicken leg meat quality, significantly improving the level of proteins and fatty acids content in breast and leg meat, respectively. More specific ω3 and ω6 fatty acids content were three times higher than in group B. Moreover, a protective effect on the decomposition of polyunsaturated fatty acids, induced by free radicals and presented in chicken meat, is based on the evaluation of lipid peroxidation by measuring thiobarbituric acid reactive substances. Pomegranate peels, avocado peels, and seed by-products appeared to have a slight reduction on meat production, while it was found to improve the qualitative chicken meat characteristics. Regarding the production costs, it was calculated that the corn-silage supplementation, used in this study, lead to a 50% lower cost than the commercial corn-silage used for the breeding of broilers. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Vacuum microwave-assisted aqueous extraction of polyphenolic compounds from avocado (Persea americana) solid waste

The extraction efficacy of avocado fruit peels (AP) and seeds (AS) with the use of vacuum microwave-assisted aqueous extraction (VMAAE) was optimized in this study, with regard to extract’s total phenolic content (TPC), maximum antioxidant activity and minimal operational cost. Temperature (79.64 and 78.11 °C for AP and 43.90 and 45.26 °C for AS), time (11.89 and 11.75 min for AP, 10.18 and 10.28 min for AS), ratio of water to raw material (16.45% and 10.02% for AP, 38.73% and 37.65% for AS) and microwave power (5708.04 and 5699.10 W for AP, 5549.08 and 4797.29 W for AS) were estimated statistically as the optimal conditions in order to achieve high rates of extracts with high TPC and antioxidant activity using the 2,2-diphenyl-1-picrylhydrazyl (DPPH●) scavenging radical methods, respectively. VMAAE performed under these conditions resulted in received extracts with TPC (0.352 gallic acid equivalent-GAE/g fresh AP/min and 0.124 GAE/g fresh AS/min). Furthermore, it was calculated the DPPH● radical scavenging activity was equal to 100 mg/L expressed in L of 0.104 L/min for AP and 0.045 L/min for AS. The results of our study may give a promising solution to avocado processing companies for further utilization of their waste. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Preliminary Studies on Suppression of Important Plant Pathogens by Using Pomegranate and Avocado Residual Peel and Seed Extracts

Potential synergistic action of aqueous extracts of pomegranate peel (PP), avocado peel (AP), and avocado seed (AS) wastes isolated by microwave-assisted extraction were assessed in in vitro and in vivo assays as biocontrol agents against several plant pathogenic fungi. The study findings contribute to the utilization of a value-added industrial byproduct and provide significant value in advancing the development of new plant protecting compositions that benefit from the synergistic effects between two important plant species that contain several natural bioactive compounds. More specifically, the in vitro results proved that the use of 100%-pure (PP) extracted waste affected the mycelium growth of Penicillium expansum. Furthermore, mycelium growth of Aspergillus niger was decreased by 10.21% compared to control after 7 days of growth in medium agar containing 100% AP and extracted waste. Moreover, mycelium growth of Botrytis cinerea was affected by equal volume of avocado extraction wastes (50% peel and 50% seed) only at the first 3 days of the inoculation, while at the seventh day of the inoculation there was no effect on the mycelium growth. Equal volumes of the examined wastes showed decreased mycelium growth of Fusarium oxysporum f.sp. lycopersici by 6%, while Rhizoctonia solani mycelium growth was found to be the most sensitive in PP application. In addition, the in vivo assay shown that PP extract suppresses damage of tomato plants caused by R. solani followed by extracted wastes from AP. Based on the research findings, it can be argued that PP and AP extracts can be used as natural antifungals instead of dangerous synthetic antifungals to effectively treat phytopathogens that cause fruit and vegetable losses during cultivation. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

The in vitro and in vivo synergistic antimicrobial activity assessment of vacuum microwave assisted aqueous extracts from pomegranate and avocado fruit peels and avocado seeds based on a mixtures design model

The present study aimed to assess the antimicrobial properties of encapsulated lyophilized powdered extracts of pomegranate peels (PP), avocado peels (AP) and avocado seeds (AS) in vitro and in vivo. Minimum Inhibitory Concentration (MIC) and Minimal Bactericidal Concentration (MBC) methods, optical density measurement, and well diffusion assay were used to determine antimicrobial activity against food borne bacteria (Gram− Escherichia coli, Salmonella typhimurium, Campylobacter jejuni, Pseudomonas putida), (Gram+ Staphylococcus aureus, Listeria monocytogenes, Clostridium perfringens, Lactobacillus plantarum), and fungi (Penicillium expansum and Aspergillus niger) based on a mixture design model. Additionally, the most effective powder was studied in vivo in yogurt, cream cheese, and minced meat burger. The samples that contained high polyphenol content also exhibited higher antioxidant, antimicrobial, and antifungal activity. From the results of the well diffusion, the MIC/MBC, and the cell optical density assays, the antimicrobial activity of the extracts was found to be correlated to the total phenolic content (TPC) of the samples and the type of the microorganism. The pomegranate peels extract presented the higher TPC and antioxidant activity and constitute the highest percentage in the most active antimicrobial mixture. The powders that were tested in vitro showed microbial type‐dependent effects in each food model. The results presented here can be further studied in the large‐scale industrial production of natural food preservatives. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Potential synergistic action of liquid olive fruit polyphenol extract with aqueous extracts of solid wastes of pomegranate or/and orange juice industry as organic phyto-protective agents against important plant pathogens - Part 1 (in vitro studies)

In this research study potential synergistic action of aqueous extracts of olive-pomegranate-orange fruits isolated by microwave assisted extraction were investigated as biocontrol agents against several plant pathogenic fungi. The aim of the research study was the production of mixed liquid extracts to be used as natural phytoprotective agents in organic farming. The results proved that the use of 100%-pure olive fruit polyphenol extract affected the mycelium growth of B. cinerea, V. dahliae, R. solani, E. lata, M. laxa, P. lycopersici and P. punicae. However, it did not affect the mycelium growth of F. oxysporum f. sp., lycopersici, A. niger, and G. graminis. Moreover, pomegranate polyphenol extract at 100% concentration inhibited mycelium growth of B. cinerea. Various olive-pomegranate-orange polyphenol aqueous extract combinations may be used in order to control the mycelium growth of the majority of the tested microorganisms. However, the use of any combination and concentrations of the tested samples (1-72) did not affect the mycelium growth of F. oxysporum f. sp., lycopersici, A. niger, and G. graminis thus, their use as biological control agent is not recommended. According to the findings of the present research, it can be suggested that the olive fruit polyphenol extract be used as potential biocontrol agent, in order to stimulate mycelium growth of various plant pathogenic fungi. Copyright © 2020 by authors, all rights reserved. Authors agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International Licens