Search Results (11)

The impact of exogenous melatonin treatment on the postharvest quality and storability of blue honeysuckle fruit was investigated. Fruits were immersed in melatonin solutions at concentrations of 0 (control), 0.01, 0.05, and 0.25 mM for 5 min and subsequently stored at –1 °C for 63 d. Among all treatments, the combination of two-week storage without fruit puncturing and 0.05 mM melatonin application significantly delayed fruit softening and decay even at the initial stage of storage, while also increasing the concentration of phenolic compounds and enhancing antioxidant activity. During the later storage period (28–63 d), melatonin-treated fruits maintained higher levels of maltose, fructose, and sucrose, contributing to improved flavor retention. In contrast, both lower (0.01 mM) and higher (0.25 mM) concentrations were less effective or even detrimental to fruit quality. HPLC-ESI-QTOF-MS² analysis revealed that 0.05 mM melatonin effectively preserved several functional phenolics, including p-coumaroylquinic acid, caffeoyl glucose, 5-O-caffeoylquinic acid, 3-O-caffeoylquinic acid, luteolin-7-O-glucoside, and hydroxytyrosol. Thus, 0.05 mM melatonin is effective in delaying senescence and maintaining the postharvest quality of blue honeysuckle fruit. Full article

The antioxidant action of terngymnoside C (1) and hydroxytyrosol-1-glucoside (2), isolated for the first time from the flower buds of Ternstroemia lineata, as well as katsumadin (3), obtained from the seedless fruits, was evaluated using ABTS^•+ and H₂O₂–Saccharomyces cerevisiae models. In silico docking analysis of 1, 2, and 3 determined their affinity forces to the aquaporin monomers of the modeled S. cerevisiae protein 3 (AQP3) and human protein 7 (AQP7) channels that regulate the H₂O₂ cell transport. The ABTS^•+ antiradical capacity of these compounds showed IC₅₀ values of 22.00 μM (1), 47.64 μM (2), and 73.93 μM (3). The S. cerevisiae antioxidant assay showed that at 25 µM (1) and 50 µM (2 and 3), the cells were protected from H₂O₂-oxidative stress. These compounds, together with quercetin and vitamin C, were explored through the modeled S. cerevisiae AQP3 and human AQP7 by molecular docking analysis. To explain these results, an antioxidant mechanism for the isolated compounds was proposed through blocking H₂O₂ passage mediated by aquaporin transport. On the other hand, 1, 2, and 3 were not cytotoxic in a panel of three cancer cell lines. Full article

CDAC (coulometrically determined antioxidant capacity) involves the determination of the antioxidant capacity of individual compounds or their mixtures using constant-current coulometry, with electrogenerated Br₂ as the titrant, and biamperometric detection of the endpoint via Br₂ excess. CDAC is an accurate, sensitive, rapid, and cheap measurement of the mol electrons (mol e⁻) transferred in a redox process. In this study, the CDAC of 48 individual antioxidants commonly found in foods has been determined. The molar ratio CDAC (CDACχ, mol e⁻ mol⁻¹) of representative antioxidants is ranked as follows: tannic acid > malvidin-3-O-glucoside ≃ curcumin > quercetin > catechin ≃ ellagic acid > gallic acid > tyrosol > BHT ≃ hydroxytyrosol > chlorogenic acid ≃ ascorbic acid ≃ Trolox^®. In many cases, the CDACχ ranking of the flavonoids did not comply with the structural motifs that promote electron or hydrogen atom transfers, known as the Bors criteria. As an accurate esteem of the stoichiometric coefficients for reactions of antioxidants with Br₂, the CDACχ provides insights into the structure–activity relationships underlying (electro)chemical reactions. The electrochemical ratio (ER), defined as the antioxidant capacity of individual compounds relative to ascorbic acid, represents a dimensionless nutritional index that can be used to estimate the antioxidant power of any foods on an additive basis. Full article

Agri-food industries generate a large amount of waste that offers great revalorization opportunities within the circular economy framework. In recent years, new methodologies for the extraction of compounds with more eco-friendly solvents have been developed, such as the case of natural deep eutectic solvents (NADES). In this study, a methodology for extracting phenolic compounds from olive tree leaves using NADES has been optimized. The conditions established as the optimal rely on a solvent composed of choline chloride and glycerol at a molar ratio of 1:5 with 30% water. The extraction was carried out at 80 °C for 2 h with constant agitation. The extracts obtained have been analyzed by high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) in MRM mode. The comparison with conventional ethanol/water extraction has shown that NADES, a more environmentally friendly alternative, has improved extraction efficiency. The main polyphenols identified in the NADES extract were Luteolin-7-O-glucoside, Oleuropein, 3-Hydroxytyrosol, Rutin, and Luteolin at the concentrations of 262, 173, 129, 34, and 29 mg kg⁻¹ fresh weight, respectively. Full article

The aim of this work was analyzing the use of olive leaf extracts (OLE) obtained from two local Tunisian olive tree cultivars ‘Chemlali’ and ’Sayali’ to reduce the acrylamide in Californian-style black olives. The phenol profile, antioxidant, and antibacterial activity of the two OLE extracts were evaluated. The principal phenols found were hydroxytyrosol (1809.6 ± 25.3 mg 100 g⁻¹), oleuropein (2662.2 ± 38 mg 100 g⁻¹) and luteolin-7-O-glucoside (438.4 ± 38 mg 100 g⁻¹) presented higher levels in ‘Sayali’ variety. Small differences were observed between the two kinds of extracts used; the greatest activity of OLE was observed against S. choleraesuis, with values up to 50% inhibition. The extract of ‘Chemlali’ cultivar was added to the Californian-style table olive, improving its phenol content and its antioxidant characteristics without negatively affecting its sensorial characteristics; these olives showed the highest firmness and proper quality characteristics. The gastrointestinal activity on the acrylamide concentration showed a partial degradation of this compound through the digestion, although the addition of the extract does not seem influence in its gastrointestinal digestion. These findings prove the usefulness of by-products to generate a high-quality added-value product, and this would also be relevant as a step towards a more sustainable, circular economy model. Full article

The extraction of phenolic compounds from olive leaves was optimized using three glycerol-based deep eutectic solvents (DESs) with lysine, proline, and arginine. A three-level Box–Behnken design was used to examine the influence of the liquid/solid ratio, concentration of DESs, and extraction temperature on the yield of the extraction process. A second-order polynomial model was used for predicting the polyphenol extraction yield. The optimal predicted conditions were used for extractions and they provided the highest total phenol yields with the glycerol–lysine exhibiting the best performance. Quantification of tyrosol, hydroxytyrosol, oleuropein, luteolin-7-O-glucoside, and rutin in the extracts showed high content in tyrosol in all DESs, particularly with glycerol–lysine and relatively similar contents with other studies for the other phenolic compounds. Finally, a linear relationship between tyrosol content and the total phenolic content of the extracts was observed. Full article

Harvest timing of oil olives is important for oil quality. Concerning the specific features of each cultivar, physiological and quality characteristics during ripening of Koroneiki olives were investigated in two successive years, A and B, from trees on full production. In A, olives were harvested at maturity indices (MIs) 0.9, 1.4, 2.1 and 4, while in B at MIs 1.1, 3.8 and 6.9. MIs ~1, ~4 and ~7 corresponded to green, red and dark purple peel in olives, respectively. Peel color parameters (L*, h° and C*), respiration and ethylene production rates were evaluated along with phenolic compounds and total antioxidant capacity (TAC) in olives of both crop years. Additionally, oil composition and a-tocopherol content were examined in olives harvested in years A and B, respectively. During fruit development, respiration and ethylene productions rates, hydroxytyrosol concentration and linoleic acid increased, while TAC, oleuropein, luteolin-7-O-glucoside, linolenic acid and α-tocopherol values decreased. Positive correlations were found among the attributes determined in both crop years that had a similar course of change during ripening, and vice versa, which could be also related to harvest timing and to quality traits of olive products. At MI ~4, at least all determined variables corresponded to oil of high quality. Practically, an early harvest might result in an olive fruit rich in antioxidants and therefore in oil production of high quality, high stability during storage and long self-life. Full article

The phenolic compound contents and antioxidant activities of the leaf extracts of nine olive genotypes were determined, and the obtained data were analysed using chemometric techniques. In the crude extracts, 12 compounds belonging to the secoiridoids, phenylethanoids, and flavonoids were identified. Oleuropein was the primary component for all genotypes, exhibiting a content of 21.0 to 98.0 mg/g extract. Hydroxytyrosol, verbascoside, luteolin 7-O-glucoside, and luteolin 4′-O-glucoside were also present in noticeable quantities. Genotypes differed to the greatest extent in the content of verbascoside (0.45–21.07 mg/g extract). The content of hydroxytyrosol ranged from 1.33 to 4.03 mg/g extract, and the aforementioned luteolin glucosides were present at 1.58–8.67 mg/g extract. The total phenolic content (TPC), DPPH^• and ABTS^•+ scavenging activities, ferric reducing antioxidant power (FRAP), and ability to inhibit the oxidation of β-carotene-linoleic acid emulsion also varied significantly among genotypes. A hierarchical cluster analysis enabled the division of genotypes into three clusters with similarity above 60% in each group. GGE biplot analysis showed olive genotypes variability with respect to phenolic compound contents and antioxidant activities. Significant correlations among TPC, FRAP, the values of both radical scavenging assays, and the content of oleuropein were found. The contents of 7-O-glucoside and 4′-O-glucoside correlated with TPC, TEAC, FRAP, and the results of the emulsion oxidation assay. Full article

Alperujo—a two-phase olive mill waste that is composed of olive vegetation water and solid skin, pulp, and seed fragments - is a highly valuable olive by-product due to its high content in phenolic compounds. In this study, we assessed whether β-cyclodextrin (β-CD), which is used to extract and protect alpejuro phenolic compounds (hydroxytyrosol-O-glucoside, tyrosol, caffeic, and p-coumaric acids) could impact on their bioaccessibility (i.e., the percentage of molecule found in the aqueous phase of the digesta) and uptake by intestinal cells, by using an in vitro digestion model and Caco-2 TC7 cells in culture, respectively. Our results showed that β-CD did not change the bioaccessibility of the selected phenols. Hydroxytyrosol-O-glucoside and caffeic did not cross Caco-2 cell monolayers. Conversely ferulic acid, identified as the main caffeic acid intestinal metabolite, was absorbed through intestinal cell monolayers (~20%). Interestingly, β-CD moderately but significantly improved the local absorption of tyrosol and p-coumaric acid (2.3 + 1.4% and 8.5 ± 4.2%, respectively, p < 0.05), even if their final bioavailability (expressed as bioaccessibility × absorption by Caco-2 cells) was not modified (16.2 ± 0.6% vs. 16.8 ± 0.5% for tyrosol and 32.0 ± 3.2% vs. 37.2 ± 3.2% for p-coumaric acid, from pure alperujo and alperujo complexed with β-CD, respectively). Overall, our results show that β-CD is an interesting extraction and storage agent for phenolic compounds that does not alter their in vitro bioavailability. Full article

The Emerald Ash Borer (EAB), Agrilus planipennis, Fairmaire, an Asian invasive alien buprestid has devastated tens of millions of ash trees (Fraxinus spp.) in North America. Foliar phytochemicals of the genus Fraxinus (Oleaceae): Fraxinus pennsylvanica (Green ash), F. americana (White ash), F. profunda (Bush) Bush. (Pumpkin ash), F. quadrangulata Michx. (Blue ash), F. nigra Marsh. (Black ash) and F. mandshurica (Manchurian ash) were investigated using HPLC-MS/MS and untargeted metabolomics. HPLC-MS/MS help identified 26 compounds, including phenolics, flavonoids and coumarins in varying amounts. Hydroxycoumarins, esculetin, esculin, fraxetin, fraxin, fraxidin and scopoletin were isolated from blue, black and Manchurian ashes. High-throughput metabolomics revealed 35 metabolites, including terpenes, secoiridoids and lignans. Metabolomic profiling indicated several upregulated putative compounds from Manchurian ash, especially fraxinol, ligstroside, oleuropin, matairesinol, pinoresinol glucoside, 8-hydroxypinoresinol-4-glucoside, verbenalin, hydroxytyrosol-1-O-glucoside, totarol and ar-artemisene. Further, dicyclomine, aphidicolin, parthenolide, famciclovir, ar-turmerone and myriocin were identified upregulated in blue ash. Principal component analysis demonstrated a clear separation between Manchurian and blue ashes from black, green, white and pumpkin ashes. The presence of defensive compounds upregulated in Manchurian ash, suggests their potential role in providing constitutive resistance to EAB, and reflects its co-evolutionary history with A. planipennis, where they appear to coexist in their native habitats. Full article

A fast, clean, energy-saving, non-toxic method for the stabilization of the antioxidant activity and the improvement of the thermal stability of oleuropein and related phenolic compounds separated from olive leaf extract via salting-out-assisted cloud point extraction (CPE) was developed using Tween 80. The process was based on the decrease of the solubility of polyphenols and the lowering of the cloud point temperature of Tween 80 due to the presence of elevated amounts of sulfates (salting-out) and the separation from the bulk solution with centrifugation. The optimum conditions were chosen based on polyphenols recovery (%), phase volume ratio (V_s/V_w) and concentration factor (F_c). The maximum recovery of polyphenols was in total 95.9%; V_s/V_w was 0.075 and F_c was 15 at the following conditions: pH 2.6, ambient temperature (25 °C), 4% Tween 80 (w/v), 35% Na₂SO₄ (w/v) and a settling time of 5 min. The total recovery of oleuropein, hydroxytyrosol, luteolin-7-O-glucoside, verbascoside and apigenin-7-O-glucoside, at optimum conditions, was 99.8%, 93.0%, 87.6%, 99.3% and 100.0%, respectively. Polyphenolic compounds entrapped in the surfactant-rich phase (V_s) showed higher thermal stability (activation energy (Ea) 23.8 kJ/mol) compared to non-entrapped ones (Ea 76.5 kJ/mol). The antioxidant activity of separated polyphenols remained unaffected as determined by the 1,1-diphenyl-2-picrylhydrazyl method. Full article