Exploiting the Potential of Bioactive Molecules Extracted by Ultrasounds from Avocado Peels-Food and Nutraceutical Applications

The Pulp, Peel, Seed, and Food Products of Persea americana as Sources of Bioactive Phytochemicals with Cardioprotective Properties: A Review

Botanically speaking, avocado (Persea americana) is a fruit. It consists of a single large seed surrounded by a creamy, smooth-textured edible mesocarp or pulp covered by a thick, bumpy skin. Avocado is a nutrient-dense fruit, containing a range of bioactive compounds which have been independently associated with cardiovascular health. These compounds have been obtained from the pulp, peel, and seed. This narrative review summarizes the current understanding of the cardioprotective potential of avocado fruit, especially the pulp and seed, and its food products, and examines the biological mechanism behind it.

Unravelling the Influence of Chlorogenic Acid on the Antioxidant Phytochemistry of Avocado (Persea americana Mill.) Fruit Peel

Oxidative stress is pivotal in the pathology of many diseases. This study investigated the antioxidant phytochemistry of avocado (Persea americana Mill.) peel. Different solvent extracts (dichloromethane, ethyl acetate, methanol, and water) of avocado peel were subjected to total phenol and flavonoid quantification, as well as in vitro radical scavenging and ferric reducing evaluation. The methanol extract was subjected to gradient column chromatographic fractionation. Fraction 8 (eluted with hexane:chloroform:methanol volume ratio of 3:6.5:0.5, respectively) was subjected to LC-MS analysis. It was assessed for cellular inhibition of lipid peroxidation and lipopolysaccharide (LPS)-induced ROS and NO production. The DPPH radical scavenging mechanism of chlorogenic acid was investigated using Density Functional Theory (DFT). The methanol extract and fraction 8 had the highest phenol content and radical scavenging activity. Chlorogenic acid (103.5 mg/mL) and 1-O-caffeoylquinic acid (102.3 mg/mL) were the most abundant phenolics in the fraction. Fraction 8 and chlorogenic acid dose-dependently inhibited in vitro (IC50 = 5.73 and 6.17 µg/mL) and cellular (IC50 = 15.9 and 9.34 µg/mL) FeSO4-induced lipid peroxidation, as well as LPS-induced ROS (IC50 = 39.6 and 28.2 µg/mL) and NO (IC50 = 63.5 and 107 µg/mL) production, while modulating antioxidant enzyme activity. The fraction and chlorogenic acid were not cytotoxic. DFT analysis suggest that an electron transfer, followed by proton transfer at carbons 3'OH and 4'OH positions may be the radical scavenging mechanism of chlorogenic acid. Considering this study is bioassay-guided, it is logical to conclude that chlorogenic acid strongly influences the antioxidant capacity of avocado fruit peel.

Application of ultrasound technology for the effective management of waste from fruit and vegetable

Food waste presents a continuous challenge for the food industry, leading to environmental pollution and economic issues. A substantial amount of waste, including by-products from fruits and vegetables, non-edible food items, and other waste materials, is produced throughout the food supply chain, from production to consumption. Recycling and valorizing waste from perishable goods is emerging as a key multidisciplinary approach within the circular bio-economy framework. This waste, rich in raw by-products, can be repurposed as a natural source of ingredients. Researchers increasingly focus on biomass valorization to extract and use components that add significant value. Traditional methods for extracting these bio-compounds typically require the use of solvents and are time-consuming, underscoring the need for innovative techniques like ultrasound (US) extraction. Wastes from the processing of fruits and vegetables in the food industry can be used to develop functional foods and edible coatings, offering protection against various environmental factors. This comprehensive review paper discusses the valorization of waste from perishable items like fruits and vegetables using US technology, not only to extract valuable components from waste but also to treat wastewater in the beverage industry. It also covers the application of biomolecules recovered from this process in the development of functional foods and packaging.

Avocado (Persea americana Mill) and its phytoconstituents: potential for cancer prevention and intervention

Dietary compounds, including fruits, vegetables, nuts, and spices, have been shown to exhibit anticancer properties due to their high concentrations of vitamins, minerals, fiber, and secondary metabolites, known as phytochemicals. Although emerging studies suggest that avocado (Persea americana Mill) displays antineoplastic properties in addition to numerous other health benefits, current literature lacks an updated comprehensive systematic review dedicated to the anticancer effects of avocado. This review aims to explore the cancer-preventive effects of avocados and the underlying molecular mechanisms. The in vitro studies suggest the various avocado-derived products and phytochemicals induced cytotoxicity, reduced cell viability, and inhibited cell proliferation. The in vivo studies revealed reduction in tumor number, size, and volume as well. The clinical studies demonstrated that avocado leaf extract increased free oxygen radical formation in larynx carcinoma tissue. Various avocado products and phytochemicals from the avocado fruit, including avocatin-B, persin, and PaDef defensin, may serve as viable cancer prevention and treatment options based on current literature. Despite many favorable outcomes, past research has been limited in scope, and more extensive and mechanism-based in vivo and randomized clinical studies should be performed before avocado-derived bioactive phytochemicals can be developed as cancer preventive agents.

Response Surface Methodology for the Optimization of Flavan-3-ols Extraction from Avocado By-Products via Sonotrode Ultrasound-Assisted Extraction

Avocado peel and seed are the main by-products of avocado processing and are considered as promising sources of phenolic compounds with biological activities. Thus, this research focuses on the establishment, for the first time, of ultrasound-assisted extraction of flavan-3-ols with high antioxidant activity from avocado peel and seed using a sonotrode. Indeed, 2 Box-Behnken designs were performed for 15 experiments, with each design having three independent factors (ratio ethanol/water (v/v), time (min) and amplitude (%)). In both models, the responses included total procyanidins (flavan-3-ols) measured via HPLC-FLD and antioxidant activity measured via DPPH, ABTS and FRAP. The results showed that applying the sonotrode extraction method could increase flavan-3-ols recovery by 54% and antioxidant activity by 62-76% compared to ultrasound bath technology. Therefore, this technology was demonstrated to be a non-thermal, low time-consuming and scalable method that allowed the recovery of flavan-3-ols from avocado by-products that could be used as functional ingredients.

Avocado peel extract loaded on chitosan nanoparticles alleviates urethane toxicity that causes lung cancer in a mouse model

Lung cancer progresses without obvious symptoms and is detected in most patients at late stages, causing a high rate of mortality. Avocado peels (AVP) were thought to be biowaste, but they have antioxidant and anticancer properties in vitro. Chitosan nanoparticles (Cs-NPs) were loaded with various plant extracts, increasing their in vitro and in vivo anticancer activities. Our goal was to load AVP onto Cs-NPs and determine the role of AVP-extract or AVP-loaded Cs-NPs in controlling the progression of lung cancer caused by urethane toxicity. The AVP-loaded chitosan nano-combination (Cs@AVP NC) was synthesized and characterized. Our in vitro results show that Cs@AVP NC has higher anticancer activity than AVP against three human cancer cell lines. The in vivo study proved the activation of apoptosis in lung cancer cells with the Cs@AVP NC oral treatment more than the AVP treatment. Additionally, Cs@AVP NC-treated animals showed significantly higher p53 and Bax-expression levels and lower NF-κB p65 levels in their lung tissues than in positive control animals. In conclusion, our study demonstrated the superior anticancer potency of Cs@AVP NC over AVP extract and its ability to inhibit lung cancer proliferation. Therefore, oral consumption of Cs@AVP NC might be a promising treatment for lung cancer.

Potential and prospects for utilization of avocado by-products in integrated biorefineries

The industrial processing of avocado to extract oil, and produce guacamole or sauces generates enormous quantities of peels and seeds (around 2 million tons worldwide in 2019) without commercially valuable applications. However, various studies have suggested the presence of a wide range of interesting compounds in the composition of these by-products. This review depicts a thorough outline of the capacity of avocado residues to be converted into a portfolio of commodities that can be employed in sectors such as the food, cosmetics, pharmaceuticals, environment, and energy industries. Therefore, a novel biorefinery strategy to valorize avocado-processing residues to obtain a polyphenolic extract, pectooligosaccharides, and succinic acid was presented. Additionally, the prospects and challenges facing a biorefinery based on the valorization of avocado residues are presented, particularly its techno-economic feasibility on an industrial scale, aiming for a resource-efficient circular bio-economy.

Deep Eutectic Solvents as a Green Tool for the Extraction of Bioactive Phenolic Compounds from Avocado Peels

Avocado peels are the main agro-industrial residue generated during the avocado processing, being a rich source of bioactive compounds like phenolic compounds. The growing demand for more sustainable processes requires the development of new and effective methods for extracting bioactive compounds from industrial waste. Deep eutectic solvents (DESs) are a new sustainable alternative to toxic organic solvents due to their non-toxicity and biocompatibility. In this study, five selected DESs were applied for the extraction of bioactive phenolic compounds from avocado peels. The extraction efficiency was evaluated by measuring the total phenolics and flavonoids content. The best extraction results were obtained with choline chloride-acetic acid and -lactic acid (92.03 ± 2.11 mg GAE/g DAP in TPC and 186.01 ± 3.27 mg RE/g DAP); however, all tested DESs show better extraction efficiency than ethanol. All the obtained NADES extracts have high antioxidant activity (FRAP: 72.5-121.1 mg TE/g; TAC: 90.0-126.1 mg AAE/g). The synthesized DESs and avocado peels DES extracts had activity against all tested bacteria (Staphylococcus aureus, Streptococcus dysgalactiae, Escherichia coli and Pseudomonas putida), and the extracts prepared with choline chloride-acetic acid and -lactic acid have the highest antibacterial activity against all microorganisms. These results, coupled with the non-toxic, biodegradable, low-cost, and environmentally friendly characteristics of DESs, provide strong evidence that DESs represent an effective alternative to organic solvents for the recovery of phenolic bioactive compounds from agro-industrial wastes.

Current Options in the Valorisation of Vine Pruning Residue for the Production of Biofuels, Biopolymers, Antioxidants, and Bio-Composites following the Concept of Biorefinery: A Review

Europe is considered the largest producer of wine worldwide, showing a high market potential. Several wastes are generated at the different stages of the wine production process, namely, vine pruning, stalks, and grape marc. Typically, these residues are not used and are commonly discarded. Portugal generates annually approximately 178 thousand metric tons of wine production waste. In this context, the interest in redirecting the use of these residues has increased due to overproduction, great availability, and low costs. The utilization of these lignocellulosic biomasses derived from the wine industry would economically benefit the producers, while mitigating impacts on the environment. These by-products can be submitted to pre-treatments (physical, chemical, and biological) for the separation of different compounds with high industrial interest, reducing the waste of agro-industrial activities and increasing industrial profitability. Particularly, vine-pruning residue, besides being a source of sugar, has high nutritional value and may serve as a source of phenolic compounds. These compounds can be obtained by bioconversion, following a concept of biorefinery. In this framework, the current routes of the valorisation of the pruning residues will be addressed and put into a circular economy context.