Fractionation and Hydrolyzation of Avocado Peel Extract: Improvement of Antibacterial Activity

Characterisation of avocado fruits from different Iberian regions: Integrating ion mobility in non-targeted LC-MS metabolomics

This study investigates the metabolic profile of Hass avocado fruits from eight Iberian regions using an advanced UHPLC-TimsTOF MS/MS analytical platform, with the hypothesis that distinct edaphoclimatic conditions give rise to region-specific metabolomic signatures. A comprehensive profiling of the methanolic extracts was performed to construct a metabolic library incorporating ion mobility descriptors. By applying unsupervised chemometrics-assisted non-targeted metabolomics, avocado fruits clustered according to geographical proximity, with the most significant metabolic differences observed between the northern and southern regions. Despite this general trend, each region exhibited distinct metabolic patterns, even between neighbouring areas. To further delineate the region-specific metabolic compositions, multiple two-class orthogonal partial least squares discriminant analysis (OPLS-DA) models were designed to identify the most influential variables in the projections, leading to the discovery of origin-specific biomarkers characteristic of avocados from each growing area. This research offers valuable information on how regional edaphoclimatic factors impact avocado quality and compositional diversity.

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.

Hass Avocado (Persea americana Mill) Peel Extract Reveals Antimicrobial and Antioxidant Properties against Verticillium theobromae, Colletotrichum musae, and Aspergillus niger Pathogens Affecting Musa acuminata Colla Species, in Ecuador

The utilization of agroindustrial residues, such as avocado peel, as a source of bioactive compounds with antioxidant properties has garnered significant attention. In this study, we investigated the antioxidant potential using the DPPH (2,2-diphenyl-1-picrylhydrazyl) and ORAC (oxygen radical absorbance capacity) methods, along with the antimicrobial activity of phenolic compounds extracted from Hass avocado peel. These soluble polyphenols were quantified and identified using high-performance liquid chromatography (HPLC). The research focused on their effects against three fungal pathogens, Verticillium theobromae, Colletotrichum musae, and Aspergillus niger, which significantly impact banana crops, an essential agricultural commodity in Ecuador. The results have revealed that the application of 80% ethanol as an organic solvent led to increased soluble polyphenol content compared to 96% ethanol. Extraction time significantly influenced the phenolic content, with the highest values obtained at 90 min. Interestingly, despite substantial mycelial growth observed across all extract concentrations, the antifungal effect varied among the pathogens. Specifically, V. theobromae exhibited the highest sensitivity, while C. musae and A. niger were less affected. These results underscore the importance of considering both antioxidant and antimicrobial properties when evaluating natural extracts for potential applications in plant disease management.

Synthesis and Isolation of Phenol- and Thiol-Derived Epicatechin Adducts Prepared from Avocado Peel Procyanidins Using Centrifugal Partition Chromatography and the Evaluation of Their Antimicrobial and Antioxidant Activity

Polyphenols from agro-food waste represent a valuable source of bioactive molecules that can be recovered to be used for their functional properties. Another option is to use them as starting material to generate molecules with new and better properties through semi-synthesis. A proanthocyanidin-rich (PACs) extract from avocado peels was used to prepare several semi-synthetic derivatives of epicatechin by acid cleavage in the presence of phenol and thiol nucleophiles. The adducts formed by this reaction were successfully purified using one-step centrifugal partition chromatography (CPC) and identified by chromatographic and spectroscopic methods. The nine derivatives showed a concentration-dependent free radical scavenging activity in the DPPH assay. All compounds were also tested against a panel of pathogenic bacterial strains formed by Listeria monocytogenes (ATCC 7644 and 19115), Staphylococcus aureus (ATCC 9144), Escherichia coli (ATCC 11775 and 25922), and Salmonella enterica (ATCC 13076). In addition, adducts were tested against two no-pathogenic strains, Limosilactobacillus fermentum UCO-979C and Lacticaseibacillus rhamnosus UCO-25A. Overall, thiol-derived adducts displayed antimicrobial properties and, in some specific cases, inhibited biofilm formation, particularly in Listeria monocytogenes (ATCC 7644). Interestingly, phenolic adducts were inactive against all the strains and could not inhibit its biofilm formation. Moreover, depending on the structure, in specific cases, biofilm formation was strongly promoted. These findings contribute to demonstrating that CPC is a powerful tool to isolate new semi-synthetic molecules using avocado peels as starting material for PACc extraction. These compounds represent new lead molecules with antioxidant and antimicrobial activity.

Natural Antimicrobials: A Reservoir to Contrast Listeria monocytogenes

Natural environments possess a reservoir of compounds exerting antimicrobial activity that are forms of defence for some organisms against others. Recently, they have become more and more attractive in the food sector due to the increasing demand for natural compounds that have the capacity to protect food from pathogenic microorganisms. Among foodborne pathogens, Listeria monocytogenes can contaminate food during production, distribution, or storage, and its presence is especially detected in fresh, raw food and ready-to-eat products. The interest in this microorganism is related to listeriosis, a severe disease with a high mortality rate that can occur after its ingestion. Starting from this premise, the present review aims to investigate plant extract and fermented plant matrices, as well as the compounds or mixtures of compounds produced during microbial fermentation processes that have anti-listeria activity.

Valorisation of Three Underutilised Native Australian Plants: Phenolic and Organic Acid Profiles and In Vitro Antimicrobial Activity

Tasmannia lanceolata, Diploglottis bracteata and Syzygium aqueum are understudied native Australian plants. This study aimed to characterise the non-anthocyanin phenolic and organic acid profiles of the aqueous extracts obtained from the leaves of T. lanceolata and fruits of D. bracteata and S. aqueum by UHPLC-Q-Orbitrap-MS/MS and UHPLC-TQ-MS/MS. A total of 39, 22, and 27 non-anthocyanin polyphenols were tentatively identified in T. lanceolata, D. bracteata, and S. aqueum extracts, respectively. Furthermore, sugars and ascorbic acid contents as well as in vitro antioxidant and antimicrobial activities of the extracts were determined. Response surface methodology was applied to achieve an extract blend with a strong inhibitory effect against Pseudomonas viridiflava, the main cause of soft rot in vegetables, Bacillus subtilis, Rhodotorula diobovata and Alternaria alternata. The identified compounds including organic acids (e.g., quinic, citric and malic acids) and polyphenols (e.g., catechin, procyanidins, and ellagitannins) might contribute to the observed antimicrobial activity. Furthermore, this study provides the most comprehensive phenolic profiles of these three underutilised native Australian plants to date.

Inhibition of Bacterial Adhesion and Biofilm Formation by Seed-Derived Ethanol Extracts from Persea americana Mill

The increase in antibiotic resistance demands innovative strategies to combat microorganisms. The current study evaluated the antibacterial and antivirulence effects of ethanol extracts from Persea americana seeds obtained by the Soxhlet (SE) and maceration (MaE) methods. The UHPLC-DAD-QTOF analysis showed mainly the presence of polyphenols and neolignan. Ethanol extracts were not cytotoxic to mammalian cells (CC50 > 500 µg/mL) and displayed a moderate antibacterial activity against Pseudomonas aeruginosa (IC50 = 87 and 187 µg/mL) and Staphylococcus aureus (IC50 = 144 and 159 µg/mL). Interestingly, no antibacterial activity was found against Escherichia coli. SE and MaE extracts were also able to significantly reduce the bacterial adhesion to A549 lung epithelial cells. Additionally, both extracts inhibited the biofilm growth at 24 h and facilitated the release of internal cell components in P. aeruginosa, which might be associated with cell membrane destabilization. Real-time PCR and agarose electrophoresis gel analysis indicated that avocado seed ethanol extracts (64 µg/mL) downregulated virulence-related factors such as mexT and lasA genes. Our results support the potential of bioproducts from P. americana seeds as anti-adhesive and anti-biofilm agents.

Biological Evaluation of Avocado Residues as a Potential Source of Bioactive Compounds

Avocado seed and peel are the main by-products from avocado industrialisation, and account for nearly 30% of fruit weight. Although they are usually discarded, their high phenolic content has been deeply associated with several nutritional and functional benefits. Thus, for a comprehensive analytical evaluation of both semi-industrial extracts, various steps have been developed: tentative characterisation and quantification of the phenolic composition using HPLC-ESI-qTOF-MS, determination of TPC and antioxidant activity by Folin–Ciocalteu, FRAP, TEAC and ORAC methods, evaluation of scavenging capacity against different ROS and measurement of the enzymatic inhibitory potential against potentially harmful enzymes. Finally, their bioactive potential was tested in a human platelet model where antiaggregatory activity was measured. Hence, 48 different compounds were identified, where flavonoids and procyanidins were the most representative groups. The higher TPC was found in avocado peel extract (190 ± 3 mg/g), which showed more antioxidant power and more capacity to decrease ROS generation than seed extract (60 ± 2 mg/g). In addition, both extracts showed enzymatic inhibition, especially against hyaluronidase, xanthine oxidase and acetylcholinesterase. Lastly, avocado peel was proven to inhibit platelet aggregation with significant results at 1, 0.75 and 0.5 mg/mL, where the extract showed reducing effects on agonists’ expression such as p-selectin or GPIIb/IIIa complex. These results demonstrate that both semi-industrial extracts—above all, avocado peel—have an interesting potential to be exploited as a natural by-product with antioxidant properties with multiple applications for the prevention of different pathologies.

Physicochemical and bioactive properties of avocado (Persea americana Mill. cv. Lorena)

Chemical compounds are of great importance in the food, cosmetic and pharmaceutical industries. Nutritional components, the presence of secondary metabolites with antioxidant and antimicrobial activity, and physicochemical properties of pulp, seed and peel of Lorena avocado cultivars were studied. Antioxidant activity was evaluated by ABTS, DPPH and lipid peroxidation in pulp, seed and peel. 26 extracts was evaluated. The results confirmed that the fruit parts stabilize free radicals and inhibit lipid oxidation processes, with the highest values in seed and peel, due to their content of flavonoids, o-diphenols and phenols. The results of phytochemical screening, antioxidant capacity and antimicrobial activity, showed significant bioprospective advantage for the presence of flavonoids, condensed tannins and total phenols in the seed, peel and pulp of Lorena avocado cultivars. Avocado fruits are rich in bioactive compounds that can be used in functional food applications.

Phenolic-Rich Plant Extracts With Antimicrobial Activity: An Alternative to Food Preservatives and Biocides?

In recent years, the search for natural plant-based antimicrobial compounds as alternatives to some synthetic food preservatives or biocides has been stimulated by sanitary, environmental, regulatory, and marketing concerns. In this context, besides their established antioxidant activity, the antimicrobial activity of many plant phenolics deserved increased attention. Indeed, industries processing agricultural plants generate considerable quantities of phenolic-rich products and by-products, which could be valuable natural sources of natural antimicrobial molecules. Plant extracts containing volatile (e.g., essential oils) and non-volatile antimicrobial molecules can be distinguished. Plant essential oils are outside the scope of this review. This review will thus provide an overview of current knowledge regarding the promises and the limits of phenolic-rich plant extracts for food preservation and biofilm control on food-contacting surfaces. After a presentation of the major groups of antimicrobial plant phenolics, of their antimicrobial activity spectrum, and of the diversity of their mechanisms of action, their most promising sources will be reviewed. Since antimicrobial activity reduction often observed when comparing in vitro and in situ activities of plant phenolics has often been reported as a limit for their application, the effects of the composition and the microstructure of the matrices in which unwanted microorganisms are present (e.g., food and/or microbial biofilms) on their activity will be discussed. Then, the different strategies of delivery of antimicrobial phenolics to promote their activity in such matrices, such as their encapsulation or their association with edible coatings or food packaging materials are presented. The possibilities offered by encapsulation or association with polymers of packaging materials or coatings to increase the stability and ease of use of plant phenolics before their application, as well as to get systems for their controlled release are presented and discussed. Finally, the necessity to consider phenolic-rich antimicrobial plant extracts in combination with other factors consistently with hurdle technology principles will be discussed. For instance, several authors recently suggested that natural phenolic-rich extracts could not only extend the shelf-life of foods by controlling bacterial contamination, but could also coexist with probiotic lactic acid bacteria in food systems to provide enhanced health benefits to human.

Antibacterial Potential by Rupture Membrane and Antioxidant Capacity of Purified Phenolic Fractions of Persea americana Leaf Extract

The present research focused on evaluating the antibacterial effect and the mechanism of action of partially purified fractions of an extract of Persea americana. Furthermore, both its antioxidant capacity and composition were evaluated. The extract was fractionated by vacuum liquid chromatography. The antimicrobial effect against Staphylococcus aureus (ATCC 6538), Escherichia coli (ATCC 11229), Pseudomonas aeruginosa (ATCC 15442), and Salmonella choleraesuis (ATCC 1070) was analyzed by microdilution and the mechanism of action by the Sytox green method. The antioxidant capacity was determined by DPPH, FRAP, and ABTS techniques and the composition by Rp-HPLC-MS. All fractions showed a concentration-dependent antibacterial effect. Fractions F3, F4, and F5 (1000 µg/mL) showed a better antibacterial effect than the extract against the bacteria mentioned. The F3 fraction showed inhibition of 95.43 ± 3.04% on S. aureus, F4 showed 93.30 ± 0.52% on E. coli, and F5 showed 88.63 ± 1.15% on S. choleraesuis and 86.46 ± 3.20% on P. aeruginosa. The most susceptible strain to the treatment with the extract was S. aureus. Therefore, in this strain, the bacterial membrane damage induced by the extract and fractions was evidenced by light fluorescence microscopy. Furthermore, the extract had better antioxidant action than each fraction. Finally, sinensitin was detected in F3 and cinnamoyl glucose, caffeoyl tartaric acid, and cyanidin 3-O-(6''-malonyl-3''-glucosyl-glucoside) were detected in F4; esculin and kaempferide, detected in F5, could be associated with the antibacterial and antioxidant effect.