Evaluation of Antioxidant Capacity (ABTS and CUPRAC) and Total Phenolic Content (Folin-Ciocalteu) Assays of Selected Fruit, Vegetables, and Spices

Functional Plant-Based Beverage Fortified with Hazelnut Cuticle Polyphenols: Antioxidant and Phenolic Content Characterization

In recent decades, there has been growing interest in the fortification of food products with antioxidants and phenolics derived from plant by-products. The present study focused on the production of a plant-based beverage enriched with hazelnut cuticle extract to characterize its antioxidant content, phenolic profile, and organoleptic characteristics. Liquid chromatography-mass spectrometry (LC-MS) enabled the identification of key polyphenols in hazelnut cuticles, including catechin, epicatechin, and quercetin derivatives, guiding the selection of a biocompatible Natural Deep Eutectic Solvent (NADES) composed of choline chloride and lactic acid for efficient extraction. The obtained phytochemical profile of the extract revealed a high concentration of bioactive compounds, with a Total Phenolic Content of 160.88 ± 14.27 mg GAE/g and Antioxidant Power measured by DPPH of 5848.2 ± 11.3 μmol TE/g. The bioaccessibility of phenolics in the fortified hazelnut-based beverage was determined after in vitro digestion, reaching a value of 89.7%, indicating excellent release and stability during digestion. Organoleptic evaluation revealed high sensory acceptability, with aftertaste scoring 3.61 ± 0.4 respect the 3.94 ± 1.3 result of reference milk, on a 5-point scale. In conclusion, this study demonstrates the potential for sustainable valorization of hazelnut cuticles, through their incorporation as NADES extracts in plant-based milk, providing an innovative solution to reduce food waste while catering to consumer demand for nutritionally enriched and eco-friendly products.

Yield and Sensorial and Nutritional Quality of Strawberry (Fragaria × ananassa Duch.) Fruits from Plants Grown Under Different Amounts of Irrigation in Soilless Cultivation

Water scarcity is an ecological issue affecting over 10% of Europe. It is intensified by rising temperatures, leading to greater evaporation and reduced precipitation. Agriculture has been confirmed as the sector accounting for the highest water consumption globally, and it faces significant challenges relating to drought, impacting crop yields and food security. Sustainable practices, precision irrigation, and the development of drought-resistant crops are essential for the mitigation of this threat. Effective, innovative solutions are crucial for optimizing water use for intensive crops such as cultivated strawberries (Fragaria × ananassa). This study emphasizes the importance of identifying the genotypes most resilient to low water availability. Experimental trials involving reduced irrigation levels were set up to identify genotypes with a greater capacity to increase fruit quality and maintain fruit yield. Reduced water conditions positively influenced strawberry fruit quality, exhibiting improved citric acid, soluble solids, and color brightness linked to decreased water use, while firmness remained stable. Notably, the total phenolic content was most affected by stress, indicating strong antioxidant responses. With these interesting variations in fruit quality came a different response in plant yield. Plants belonging to the Lauretta and AN15,07,53 cultivars maintained a 98% fruit yield when grown under WS1 conditions. While the yield for the Francesca cultivar increased by 10% under the stressed WS1 conditions in comparison to the control conditions, water stress in the WS2 treatment caused a strong reduction in yield in all three genotypes. Overall, the findings emphasize the importance of identifying for each new cultivar the most appropriate water regime in order to amplify the quality of the fruit, thus maintaining high production standards and saving water.

Ultrasound-Assisted Extraction of Squalene and 2-Acetyl-1-Pyrroline from Pandan Leaf: The Effects of Drying Methods and Extraction Conditions

Pandan, a tropical crop, is rich in squalene (SQ), known for its antioxidant and hypoglycemic properties, and 2-acetyl-1-pyrroline (2-AP), which imparts a characteristic aroma. This study focuses on the extraction of the two bioactive compounds from Pandan leaves and investigates the effects of drying methods, extraction solvents, and conditions on the yield of SQ and 2-AP. Results show that hot air-dried Pandan leaves when extracted using the binary solvent system of ethanol and n-hexane (EH), yield higher SQ content while maintaining an adequate content of 2-AP. To further optimize the extraction process, a single-factor experiment was followed by optimization using Box-Behnken design (BBD) and response surface methodology (RSM). The optimal extraction conditions were determined as follows: ultrasound time of 60 min, a temperature of 50 °C, power of 300 W, and a solid-to-liquid ratio of 1:5 g/mL. Under these conditions, an SQ yield of 1229.98 ± 13.09 μg/DW 1 g Pandan leaves and a 2-AP yield of 80.72 ± 0.88 μg/DW 1 g Pandan leaves were achieved, representing increases of 3.30% and 9.82% compared to pre-optimization values. Additionally, the antioxidant activities of EH extracts were evaluated through various in vitro assays. The extracts demonstrated significant DPPH and ABTS free radical scavenging activity (12.46 μmol TE/g DW and 22.14 μmol TE/g DW, respectively), along with ferric and cupric ion reducing power (10.629 μmol TE/g DW and 14.275 μmol TE/g DW, respectively). The extracts also exhibited notable inhibitory effects on α-amylase and α-glucosidase. The findings suggest that these extracts are a promising natural source of antioxidants with potential applications in health and nutrition.

A comprehensive and critical review of the unstandardized Folin-Ciocalteu assay to determine the total content of polyphenols: The conundrum of the experimental factors and method validation

The Folin-Ciocalteu method can be considered to be the most widely used in laboratories around the world, to quantify the total polyphenols content. Many different variations found in this assay have been reported in the scientific literature. In this review, the full experimental conditions influencing the Folin-Ciocalteu assay have been comparatively assessed and discussed. Furthermore, few studies relating to the method validation have been evaluated according to the results of selectivity, linearity, precision, trueness, limit of determination, limit of quantification and robustness. In general, the results derived from the reviewed literature are widely variable according to both, the experimental factors selected and the performance parameters reported, making difficult the comparison of the overall results published.

Quercetin, a Flavonoid with Great Pharmacological Capacity

Quercetin is a flavonoid with a low molecular weight that belongs to the human diet's phenolic phytochemicals and nonenergy constituents. Quercetin has a potent antioxidant capacity, being able to capture reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive chlorine species (ROC), which act as reducing agents by chelating transition-metal ions. Its structure has five functional hydroxyl groups, which work as electron donors and are responsible for capturing free radicals. In addition to its antioxidant capacity, different pharmacological properties of quercetin have been described, such as carcinostatic properties; antiviral, antihypertensive, and anti-inflammatory properties; the ability to protect low-density lipoprotein (LDL) oxidation, and the ability to inhibit angiogenesis; these are developed in this review.

Catechin Composition, Phenolic Content, and Antioxidant Properties of Commercially-Available Bagged, Gunpowder, and Matcha Green Teas

The leaves of the Camellia sinensis plant are used to produce many different types of teas, and green tea is particularly noted for its health promoting properties which are attributed to high concentrations of phenolic compounds known as catechins. Green tea is available in forms such as bagged, gunpowder (rolled leaf), and matcha, a fine powder. This study evaluated the phenolic content, catechin composition, caffeine concentration, and antioxidant properties of fifteen commercially-available green teas with an emphasis on identifying differences between ceremonial and culinary matcha. Gunpowder and bagged green teas had higher total phenolic contents and greater CUPRAC (cupric ion reducing antioxidant capacity) and ORAC (oxygen radical absorbance capacity) antioxidant capacities than matcha teas. Among matcha samples, less expensive culinary teas had greater total phenolic contents and higher antioxidant capacities than ceremonial products. Hierarchical cluster analysis was used to determine similarities and differences in catechin composition and revealed that bagged and gunpowder green teas had the highest levels of the stereoisomers epi/catechin gallate, which correlated with their strong antioxidant properties. Bagged and gunpowder teas were the lowest cost products in this study, indicating that they are an economical choice for consumers who want a green tea beverage with high catechin content, although they generally had lower caffeine levels than matcha.

Discrimination of Green Coffee (Coffea arabica and Coffea canephora) of Different Geographical Origin Based on Antioxidant Activity, High-Throughput Metabolomics, and DNA RFLP Fingerprinting

The genus Coffea is known for the two species C. arabica (CA) and C. canephora (CC), which are used to prepare the beverage coffee. Proper identification of green beans of coffee varieties is based on phenotypic and phytochemical/molecular characteristics. In this work, a combination of chemical (UV/Vis, HPLC-DAD-MS/MS, GC-MS, and GC-FID) and molecular (PCR-RFLP) fingerprinting was used to discriminate commercial green coffee accessions from different geographical origin. The highest content of polyphenols and flavonoids was always found in CC accessions, whereas CA showed lower values. ABTS and FRAP assays showed a significant correlation between phenolic content and antioxidant activity in most CC accessions. We identified 32 different compounds, including 28 flavonoids and four N-containing compounds. The highest contents of caffeine and melatonin were detected in CC accessions, whereas the highest levels of quercetin and kaempferol derivatives were found in CA accessions. Fatty acids of CC accessions were characterized by low levels of linoleic and cis octadecenoic acid and high amounts of elaidic acid and myristic acid. Discrimination of species according to their geographical origin was achieved using high-throughput data analysis, combining all measured parameters. Lastly, PCR-RFLP analysis was instrumental for the identification of recognition markers for the majority of accessions. Using the restriction enzyme AluI on the trnL-trnF region, we clearly discriminated C. canephora from C. arabica, whereas the cleavage performed by the restriction enzymes MseI and XholI on the 5S-rRNA-NTS region produced specific discrimination patterns useful for the correct identification of the different coffee accessions. This work extends our previous studies and provides new information on the complete flavonoid profile, combining high-throughput data with DNA fingerprinting to assess the geographical discrimination of green coffee.

The Biochemistry and Effectiveness of Antioxidants in Food, Fruits, and Marine Algae

It is more effective to maintain good health than to regain it after losing it. This work focuses on the biochemical defense mechanisms against free radicals and their role in building and maintaining antioxidant shields, aiming to show how to balance, as much as possible, the situations in which we are exposed to free radicals. To achieve this aim, foods, fruits, and marine algae with a high antioxidant content should constitute the basis of nutritional elements, since natural products are known to have significantly greater assimilation efficiency. This review also gives the perspective in which the use of antioxidants can extend the life of food products, by protecting them from damage caused by oxidation as well as their use as food additives.