Search Results (128)

Polyphenols are natural compounds with antioxidant properties that help prevent chronic diseases. Red onion (Allium cepa) peels are an underutilized source of polyphenols, offering a sustainable opportunity for the valorization of agricultural by-products. Polyphenol-rich extracts were obtained from red onion peels using subcritical water extraction and adsorption resin chromatography. Their biological effects were evaluated in Caenorhabditis elegans under oxidative stress conditions. A multi-omics approach integrating transcriptomics, metabolomics, and lipidomics was applied to assess molecular responses. The extract exhibited a high total phenolic content (>400 mg GAE/g) and strong antioxidant capacity, supporting a highly enriched polyphenolic profile. Survival assays confirmed the absence of toxicity at 100 µg/mL GAE. Transcriptomic analysis revealed 158 differentially expressed genes associated with stress response and metabolic regulation. Metabolomic profiling indicated a systematic reduction in amino acid levels alongside an increase in betaine in treated worms, suggesting adaptive metabolic reprogramming. Lipidomic analysis revealed significant lipid remodeling, characterized by decreased triglycerides, increased diacylglycerols, and changes in membrane phospholipids, indicating alterations in membrane composition and cellular responses associated with oxidative stress adaptation. Together, these results support a model in which red onion peel extracts induce coordinated transcriptional and metabolic adaptations associated with cellular resilience and stress adaptation. This study highlights the potential of agro-industrial by-products as functional bioactive ingredients and demonstrates the value of multi-omics approaches for uncovering system-level responses. Full article

Deep eutectic solvents (DES) emerge as sustainable alternatives for antioxidant polyphenol extraction; however, their analytical performance and compatibility with antioxidant assays remain insufficiently characterized. A choline chloride-urea-water DES (1:2:4) was compared with 70% ethanol for extracting polyphenols from onion bulbs and peels from cultivars grown in Spain and North Macedonia. Extraction conditions were selected through a comparative evaluation of vortex- and ultrasound-assisted extraction and benchmarked against conventional ethanolic stirring (2 h). Two-way ANOVA identified solvent composition as the main determinant of total phenolic content (F(1,20) = 1526.28, p < 0.001), while extraction method significantly influenced recovery under DES conditions (F(2,30) = 408.52, p < 0.001). The selected UAE-DES protocol increased TPC up to 2.2-fold and reduced extraction time to <5 min. TPC ranged from 25 to 44 mg GAE/g dw in bulbs and 42–62 mg GAE/g dw in peels, with red cultivars showing the highest values. UHPLC-MS/MS revealed solvent-dependent selectivity: ethanol favored flavonols (quercetin 5–11 mg/g dw), whereas DES enhanced phenolic acids (gallic acid up to 0.3 mg/g dw; protocatechuic acid up to 7 mg/g dw). FRAP correlated with TPC (r = 0.64–0.92), while ABTS was incompatible with DES extracts. Storage reduced TPC by 45–75% but preserved cultivar ranking. These findings demonstrate that UAE-DES enables rapid and efficient polyphenol recovery while highlighting the need to validate antioxidant assays in non-conventional solvents. Full article

Four onion (Allium cepa L.) cultivars with different bulb colors (yellow Y14, red R12, red R10 and white W3) were characterized for phenotypic, metabolic, volatile, antioxidant, flavor and transcriptomic variations, to unravel key metabolites and molecular mechanisms responsible for quality differentiation. Y14 possessed the maximum bulb weight (535.34 g) and diameter (13.10 cm), along with the highest total phenolic content (3.10 mg·g⁻¹), showing superior yield and antioxidant properties. In R12, upregulated expression of carotenoid biosynthetic genes enhanced carotenoid accumulation, resulting in vivid bulb color. R10 had high total phenols (3.89 mg·g⁻¹) and the richest sweet-associated volatiles, featuring strong antioxidant activity and distinct sweetness. By contrast, W3 exhibited moderate flavor but inferior performance in yield, antioxidant capacity, pigment and volatile levels relative to the other three cultivars. Comprehensive assessment indicated that Y14 serves as an excellent processing material, R12 and R10 are ideal for fresh consumption and functional food development, and W3 is well-suited for raw salads. This study lays a theoretical foundation for onion quality improvement, targeted breeding and efficient utilization. Full article

The effects of ambient storage (A), cold storage (C), and frozen storage (F) on the quality, metabolomic characteristics, and sulfur-related aroma of red onion ‘Kewei Red 10’ (R10) and yellow onion ‘Kewei Yellow 14’ (Y14) were investigated using integrated non-targeted and volatile metabolomics. Ambient storage accelerated shrinkage, firmness loss, and sensory deterioration in both cultivars, whereas low-temperature storage effectively delayed quality decline. R10 exhibited better tolerance to frozen storage, while Y14 performed better under cold storage. Metabolomic analysis revealed that amino acids and lipid-related metabolites were closely associated with onion senescence in both cultivars. In contrast, flavonoids were enriched in preservation-associated subclasses in R10, whereas organic acids and their derivatives were more strongly associated with delayed senescence in Y14. Volatile metabolomic analysis identified sulfur compounds and heterocyclic sulfur compounds as the major contributors to onion aroma. Sulfur-related volatiles showed distinct cultivar-dependent accumulation patterns, with many sulfur compounds accumulating prominently in ambient-stored R10-A, whereas cold-stored Y14-C maintained relatively higher levels of characteristic onion-like aroma compounds. These findings demonstrate distinct metabolic adaptation strategies between red and yellow onions during storage and suggest that cultivar-specific storage conditions are required to optimize both shelf life and flavor quality. Full article

Optimizing nutrient uptake efficiency (NUE) through an understanding of system-level dynamics and crop-specific physiological thresholds is essential for the resilience of North European vegetable production under shifting climatic conditions. This study evaluated the uptake and efficiency of macro- and secondary nutrients (N, P, K, Ca, Mg) in cabbage, carrot, red beet, and onion over a five-year period (2021–2025) in Latvia, comparing organic and integrated management systems. It was hypothesized that NUE on commercial farms is currently suboptimal due to standardized bulk applications and that systems integrating sustainable practices would demonstrate higher nutrient uptake efficiency than those relying exclusively on mineral fertilization. The results revealed a notable yield–input divergence, where increased fertilization rates failed to provide proportional yield gains, as evidenced by the lack of a strong linear relationship (R² < 0.07) and variable correlation coefficients (e.g., r = 0.52 for N in cabbage and r = −0.47 for Ca in carrot). These findings suggest that abiotic stressors and technical constraints may outweigh the influence of nutrient volume alone. This divergence was less pronounced in organic farming systems compared to integrated ones and varied notably by crop. Such species-specific responses indicate a complex role for mineral nutrition in root crops that requires further physiological investigation. No consistent differences in nutrient concentrations were observed between farming systems, indicating that inter-annual climatic variability is the dominant driver of nutrient dynamics. Furthermore, the integration of green manures and supplemental irrigation triggered extreme apparent system-level N-NUE values (exceeding 500% in some cases), reflecting the successful mineralization of legacy nitrogen and enhanced mass flow to the root zone. The study concludes that current fertilization methodologies in the Baltic region may lead to over-application. To ensure climate-resilient horticulture, management strategies must transition toward balancing ionic ratios (Ca:K) and synchronizing inputs with specific crop removal rates, rather than relying on standardized bulk applications. Full article

Onion peel represents a valuable food by-product rich in bioactive phenolic compounds. Building on previous phytochemical investigations, an onion peel extract from the Rossadi Tropea variety was developed as a standardized bioactive ingredient (OPI-T), defined by flavonol (quercetin and its glycosylated and oxidized derivatives) and anthocyanin (cyanidin derivatives) markers, ensuring batch-to-batch consistency, and evaluated for its potential against hepatic steatosis. The present study aimed to assess the protective effects of OPI-T against palmitate-induced steatosis and oxidative stress in HepG2 cells, a widely used in vitro model of hepatic lipid accumulation. An onion peel extract derived from the Ramata di Montoro variety was included as a natural negative reference to account for varietal variability. HepG2 cells were co-treated with palmitate (500 µM) and OPI-T (25 or 50 µg/mL). Lipid accumulation was evaluated by Oil Red O and BODIPY staining, while oxidative stress was assessed by the DCF assay. Mitochondrial dynamics and autophagy were investigated through the analysis of key protein markers, including MFN2, DRP1, SQSTM1/p62 and LC3 II/I. OPI-T significantly attenuated palmitate-induced lipid accumulation (−18%) and reduced intracellular ROS production (−75%), while modulating mitochondrial dynamics toward a reduced fission phenotype with a marked increase in the MFN2/DRP1 ratio (1.66) and improving autophagy flux. In contrast, the Ramata di Montoro variety showed weaker or inconsistent effects under the same experimental conditions. Overall, these findings support the functional validation of a standardized onion peel-derived ingredient, highlighting its potential application as a bioactive component for functional food or nutraceutical development targeting hepatic steatosis and oxidative stress. Full article

Background/Objectives: Onion (Allium cepa) peems are an underutilized by-product rich in polyphenols. This study evaluated the physicochemical profile, and bioactive potential (antidiabetic, antimicrobial, antioxidant, and anticoagulant) of Moroccan red onion peels using integrated in vivo, in vitro, and in silico approaches. Methods: Moisture, pH, ash content, and mineral elements were determined, followed by phytochemical screening and three extractions: decoction E0, aqueous Soxhlet E1, and hydroethanolic Soxhlet E2 (70/30; ethanol/water, v/v). The measurement of polyphenols, flavonoids, and tannins was carried out using colorimetric methods, while the molecular profile was studied by high-performance liquid chromatography coupled to ultraviolet detection and electrospray ionization mass spectrometry (HPLC/UV-ESI-MS). Biological activities were determined using 2,2-diphenyl-1-picrylhydrazyl, ferric reducing antioxidant power, and total antioxidant capacity assays (in vitro antioxidant); microdilution (antimicrobial); prothrombin time and activated partial thromboplastin time (anticoagulant); and α-amylase/α-glucosidase enzymatic inhibition and oral glucose tolerance tests on normoglycemic rats. Also, acute toxicity was evaluated, and molecular interactions between these proteins and ligands (docking, molecular dynamics, and MM-PBSA) were analyzed. Results: Physicochemical analyses showed an acidic pH (3.06) and high ash content (15.21%), with the concentration of regulated elements remaining within FAO/WHO limits. The extractive content was between 6.90% E0 and 19.18% E2. The E1 extract had the maximum amount of total polyphenols (178.95 mg GAE/g); on the other hand, E2 was the richest in flavonoids by 121.43 mg QE/g. The HPLC/ESI-MS analysis of E0 revealed 20 compounds, among which flavonoids (84.93%) were predominant, with isorhamnetin (30.26%), followed by quercetin and its glycosylated forms. E1 showed the most potent antioxidant effects (IC₅₀ DPPH, 22.38 µg/mL, as that of ascorbic acid). The antibacterial activity of E0 was especially potent towards Enterobacter cloacae and Pseudomonas aeruginosa (MIC 75 µg/mL). A mild dose-dependent anticoagulant effect was seen. Antidiabetic activity was found to be outstanding: α-amylase (IC₅₀ 62.75 µg/mL) and α-glucosidase (IC₅₀ 8.49 µg/mL, stronger than acarbose) inhibitions were corroborated in vivo by a considerable decrease in the glycemic area under the curve. The molecular docking study in silico demonstrated strong molecular interactions, especially for quercetin 4′-O-glucoside with good binding energies. Conclusions: A. cepa peels from Morocco can be considered a safe plant matrix containing bioactive flavonoids with strong antioxidant and selective antimicrobial activities and promising antidiabetic effects, supported by molecular modeling. Full article

Onion bulbs are a primary source of health-promoting fructooligosaccharides (FOS), which significantly degrade during long-term storage. This study investigated the potential of osmotic dehydration in a concentrate containing FOS (55.3% DM) to restore FOS levels in stored onions. The available data lack information on the use of osmoconcentration for this purpose. Four cultivars (Alonso F1, Hysky F1, Hystore F1, and Red Lady F1) were evaluated after four months of storage. Two 40% hypertonic solutions, a saccharose control and a fructooligosaccharide concentrate were used. Mass migration indicators, including water loss, weight reduction, and solid gain, were determined alongside HPLC-RI analysis of the saccharide profile. Results showed that storage caused an approximately 50% reduction in the initial FOS content (approx. 4 g/100 g). Osmotic dehydration using the FOS concentrate increased FOS levels approximately threefold compared to the saccharose treatment, effectively restoring or exceeding post-harvest concentrations. Red Lady demonstrated the highest water loss (28.9%), while Hystore exhibited the greatest solid gain (9.8%). In conclusion, osmotic dehydration with FOS-rich solutions is an effective method for the functionalization of stored onion raw material. This approach successfully compensates for physiological losses during storage and allows for precise modification of the nutritional profile of the bulbs without compromising osmoconcentration efficiency. Full article

Green-synthesis routes for producing CuO nanoparticles offer a simplified, sustainable, and low-cost replacement for conventional chemical methods, eliminating the need for harsh chemicals and providing an easily scalable process for industrial-level production. Although numerous studies have investigated synthesizing CuO nanoparticles from single plant extracts, comparative assessments of multi-plant-mediated CuO nanoparticles alongside synthetic CuO remain limited. In this work, CuO nanoparticles were green-synthesized from three different plant sources, namely ginger, red onion peels, and garlic, and their physicochemical and biological properties were tested against the synthetic CuO. All plant extracts produced pure-phased monoclinic CuO nanoparticles as confirmed by UV–Vis, XRD, FTIR, and SEM/EDX analyses. SEM showed distinct nanoparticle morphologies, with CuO from ginger extract exhibiting uniform nanocubes, while nanoparticles from red onion and garlic extracts exhibited more aggregated and irregular structures. Their crystallite sizes were 8–9 nm lower than the ~11 nm observed for the synthetic CuO, highlighting the phytochemical role in shaping the nanoparticles’ morphology. The antibacterial efficacy against S. aureus and E. coli showed that ginger-derived and synthetic CuO had the strongest bacterial inhibition and bactericidal potency compared to onion- and garlic-derived CuO samples. However, synthetic CuO had the highest cytotoxicity risk, hindering its suitability for biological uses, while CuO-ginger maintained good cell viability at moderate concentrations. CuO-onion and CuO-garlic gave lower antibacterial cytocompatibility performance due to their thicker capping layers, which led to decreased Cu²⁺ release and ROS production. Ginger-derived CuO achieved an optimal trade-off between antibacterial and cytotoxic efficiency, highlighting its prospects as a candidate for biomedical applications. Full article

Onions represent one of the most widely consumed vegetables within the Allium genus, generating a significant amount of waste. Onion waste is mainly composed of non-edible fractions, including roots, outer dry skins, and the outer fleshy scale. This study aimed to valorize red onion waste (ROW) and assess its total phenolic content and antioxidant activity using a water bath extraction method with distilled water as the extraction solvent. response surface methodology was employed to optimize the extraction parameters, namely temperature and time. The phenolic composition of freeze-dried ROW extract was analyzed using liquid chromatography–mass spectrometry analysis. The antibacterial activity was assessed using the disk diffusion and broth dilution methods against Gram-positive and Gram-negative bacteria, and the anticancer activity was tested against H460 lung, Caco-2 colon, and HT-29 colorectal cancer cell lines. The ideal extraction parameters were 1:40 g/mL, 98 °C for 27 min. The major detected compounds were isorhamnetin (55.32%), hyperoside (19.44%), and quercetin (13.65%). ROW extract showed antibacterial activity against Bacillus cereus, Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, Pseudomonas aeruginosa, and Salmonella Typhimurium, with the highest activity observed against S. aureus. A cytotoxic effect against H460 and Caco-2 was shown by the ROW extract, with IC₅₀ values detected within the tested concentrations. The results suggest that ROW extract has potential for effective application as an antioxidant, antibacterial, and anticancer agent, demonstrating its potential for incorporation into functional foods and nutraceutical development. Full article

In Chinese cuisine, seasoning oil enhances the aroma and appearance of dishes. This study examined how processing affects flavor release in multi-ingredient oils. Volatile organic compounds (VOCs), relative odor activity value (ROAV), and variable importance projection (VIP) were used to assess flavor changes. Optimal frying was 160 °C for 15 min with 11% green Sichuan peppercorn, 3% ghost pepper, 6% green onion, 0.1% bay leaf, 0.2% deseeded tsaoko, 0.5% star anise, 0.3% fennel seeds, 1.5% dried Erjingtiao chili, 5% ginger, and 2.5% red Sichuan peppercorn. Gas chromatography–ion mobility spectrometry (GC-IMS) and gas chromatography–mass spectrometry (GC-MS) analyzed heating at 150 °C, 160 °C, and 170 °C. Temperature strongly influenced VOC formation; 160 °C produced the most diverse VOCs, including aldehydes, ketones, terpenes, esters, and alcohols. Multivariate analysis identified 73 key compounds (VIP > 1) between 150 and 160 °C, but only 39 between 160 and 170 °C, indicating that high heat reduces complexity. Compounds such as 2-methylpyrazine and (E)-2-heptenal contributed caramel, nutty, buttery notes, with 2-methoxy-3-(1-methylethyl)-pyrazine as the core aroma. Frying at 160 °C balanced sweet, floral, and roasted aromas, offering guidance for precise seasoning oil flavor control. Full article

The bioaccessibility of flavonoids (namely, their release from the food matrix and their stability under gastrointestinal conditions) is pivotal in establishing their bioavailability and biological effects. Bioaccessibility is affected by several factors, including the food matrix. Previous studies suggested that flavonols and flavan-3-ols were higher in solid foods rather than in beverages. Therefore, this study investigated the bioaccessibility of red-skinned onion flavonols and dark chocolate flavan-3-ols during in vitro gastrointestinal digestion of whole foods and the corresponding phenolic compounds extracts, with the aim of ascertaining a possible food matrix effect. Results showed that the presence of the food matrix protected flavonols and flavan-3-ols from degradation during digestion. The bioaccessibility of total flavonols and flavan-3-ols determined by mass spectrometry was 79.0% and 80.8% for red-skinned onion and dark chocolate, respectively, whereas it was 57.5% and 47.3% for the corresponding extracts. Degradation of flavonols occurred mainly during intestinal digestion by deglycosylation and oxidative reactions, whereas for flavan-3-ols, it occurred during gastric digestion mainly by hydrolysis. Therefore, this study highlighted the importance of the food matrix in protecting flavonols and flavan-3-ols from degradation during digestion, underscoring the significance of consuming phenolic compounds in whole foods rather than supplements or extracts. Full article

Onion (Allium cepa L.) peels represent a major agro-industrial by-product and are a rich source of polyphenols, with recognized antioxidant properties. This study compared the polyphenolic profile of two onion cultivars peels: red “Rossa di Tropea” and yellow “Recas”. Their digestive stability, intestinal bioavailability, and antioxidant activity were evaluated. Hydroalcoholic extracts were characterized by HPLC-DAD, subjected to a static gastrointestinal digestion model, and assessed for transport across differentiated Caco-2 monolayers. Antioxidant properties were determined using DPPH, FRAP, Cellular Antioxidant Activity (CAA), and intracellular glutathione (GSH) assays. Red peels contained a higher total polyphenol content (28.44 mg/g DW) than yellow peels (15.61 mg/g DW), including anthocyanins uniquely present in the red cultivar. Digestive stability varied markedly between cultivars, with yellow peels showing greater intestinal recovery (72.7%) than red peels (49.1%). Glycosylated flavonols were more stable and exhibited moderate intestinal transport (Papp = 1.1–9.9 × 10⁻⁶ cm·s⁻¹), whereas quercetin aglycone showed low permeability. Red peel extracts demonstrated stronger chemical antioxidant activity, while yellow peels were more effective in cell-based assays, displaying higher CAA values and inducing a pronounced increase in intracellular GSH. Overall, onion peel extracts exhibit promising antioxidant and biological properties. However, their limited bioavailability highlights the need for formulation strategies to enhance gastrointestinal stability and intestinal uptake, supporting their potential use as sustainable functional ingredients. Full article

Cysteine (Cys) is an essential thiol in food and biological systems, yet its selective quantification remains challenging due to interference from structurally related analytes such as homocysteine (Hcy) and glutathione (GSH). Here, we report a hemicyanine-based, turn-off fluorescent probe (PRH) that undergoes Cys-triggered cyclization to release PRH-OH, resulting in fluorescence quenching. PRH exhibits near-infrared emission at 630 nm, enabling low self-absorption and reduced background. The probe affords a broad linear range (0–100 μM) with a detection limit of 0.344 μM, along with high selectivity over Hcy, GSH, and 18 other amino acids. In food matrices (garlic, onion, and dried red pepper), PRH achieved recoveries of 98.8–101.3% with RSD < 2% (n = 3), demonstrating analytical robustness. Live-cell imaging in HeLa cells further verified practical responsiveness: N-ethylmaleimide-mediated thiol depletion increased PRH fluorescence, whereas Cys replenishment decreased it, consistent with the probe’s turn-off behavior. DFT calculations support an intramolecular charge-transfer change upon Cys reaction, correlating with the observed spectral shift. Overall, PRH provides a simple and selective platform for reliable Cys quantification in food samples and for visualizing Cys dynamics in cells. Full article

The current study aimed to fortify fresh pasta with red onion peels in the form of powder (OPP). For this aim, three concentrations were used (3%, 6%, and 9% w/w) and properly added to the dough. A control sample was also prepared for comparison (CTRL). Raw and cooked pasta samples were assessed for sensory acceptability and technological properties. Fibre content, total polyphenols, and antioxidant activity (by ABTS and FRAP) were assessed in raw materials and pasta samples. The glycaemic index was also predicted. Results from sensory evaluation and technological analyses demonstrated that with increasing OPP, some defects were perceived to provoke a complete unacceptance with the highest fortification level (9% score < 5). However, these effects were counterbalanced by a significant functional quality increase in fibre content, total polyphenols, and antioxidant activity, justified by the presence of the new onion-based ingredient. Therefore, to better balance benefits and drawbacks of onion peel recycling, a global quality index (GQI) was calculated, which accounted for nutritional improvements and sensory worsening. The most interesting GQI values were found for both 3% and 6% levels of fortification (52.58 vs. 51.86). Considering that these values are very comparable, the 6% can be considered the optimal concentration because it represents the highest concentration to give a fortified and sensorially friendly product. Full article