Honey and Its Biomimetic Deep Eutectic Solvent Modulate the Antioxidant Activity of Polyphenols

Honey is a highly valued natural product with antioxidant, antimicrobial and anti-inflammatory properties. However, its antioxidant activity (AOA) is not as high as that of other honeybee products, such as propolis. Several polyphenol-honey formulations have been proposed up to now, most of them using maceration of biomass in honey or mixtures with liquid extracts, which either limit polyphenols bioavailability or destroy the characteristics of honey. To improve the health benefits of honey by increasing AOA and keeping its structural and sensory properties, we propose its enrichment in a polyphenol extract of raspberry after solvent evaporation. A honey-biomimetic natural deep eutectic solvent (NaDES) was prepared and compared with honey. The main polyphenols found in the raspberry extract were tested in combination with honey and NaDES, respectively. The AOA was determined by DPPH, ABTS, CUPRAC, and FRAP methods. The AOA behaviour of honey-polyphenol mixtures varied from synergism to antagonism, being influenced by the AOA method, polyphenol type, and/or mixture concentration. The honey-biomimetic NaDES resulted in similar AOA behaviour as with honey mixed with polyphenols. Honey seems to have additional properties that increase synergism or reduce antagonism in some cases. Honey and its biomimetic NaDES modulate AOA of polyphenols extract.

Fortification of Pectin/Blackberry Hydrogels with Apple Fibers: Effect on Phenolics, Antioxidant Activity and Inhibition of α-Glucosidase

The objective of this study was to prepare hydrogels based on pectin and blackberry juice and additionally to fortify those hydrogels with apple fiber. For that purpose, two types of pectin (low methoxylated and high methoxylated) were used, and fortification was conducted with the addition of 10% of apple fiber. The hydrogels were evaluated for phenolic compounds, antioxidant activity and inhibition of α-glucosidase. In addition, the stability of these parameters after 8 months of storage was evaluated. Pectin type and addition of apple fiber had an impact on investigated parameters. Low methoxylated pectin hydrogels had a higher concentration of anthocyanins than high methoxylated pectin hydrogels, while the addition of apple fibers caused a decrease in anthocyanin content. However, fortified hydrogels had higher antioxidant activity due to the presence of phenolics from apple fibers. The results showed that anthocyanins were more favorable in inhibiting α-glucosidase because samples with higher anthocyanins concentration had lower IC₅₀ values. Obtained hydrogels can be used as intermediate products or ingredients (like fruit fillings or spreads) for the improvement or development of novel food products to increase their fiber content and antioxidant potential.

The Combination of Mild Salinity Conditions and Exogenously Applied Phenolics Modulates Functional Traits in Lettuce

The quest for sustainable strategies aimed at increasing the bioactive properties of plant-based foods has grown quickly. In this work, we investigated the impact of exogenously applied phenolics, i.e., chlorogenic acid (CGA), hesperidin (HES), and their combinations (HES + CGA), on Lactuca sativa L. grown under normal- and mild-salinity conditions. To this aim, the phenolic profile, antioxidant properties, and enzyme inhibitory activity were determined. The untargeted metabolomics profiling revealed that lettuce treated with CGA under non-stressed conditions exhibited the highest total phenolic content (35.98 mg Eq./g). Lettuce samples grown under salt stress showed lower phenolic contents, except for lettuce treated with HES or HES + CGA, when comparing the same treatment between the two conditions. Furthermore, the antioxidant capacity was investigated through DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,20-azinobis-(3-ethylbenzothiazoline-6-sulfonate)), and FRAP (ferric reducing antioxidant power) assays, coupled with metal-chelating activity and phosphomolybdenum capacity. An exciting increase in radical scavenging capacity was observed in lettuce treated with exogenous phenolics, in both stress and non-stress conditions. The inhibitory activity of the samples was evaluated against target health-related enzymes, namely cholinesterases (acetylcholinesterase; AChE; butyryl cholinesterase; BChE), tyrosinase, α-amylase, and α-glucosidase. Lettuce treated with HES + CGA under non-stress conditions exhibited the strongest inhibition against AChE and BChE, while the same treatment under salinity conditions resulted in the highest inhibition capacity against α-amylase. Additionally, CGA under non-stress conditions exhibited the best inhibitory effect against tyrosinase. All the functional traits investigated were significantly modulated by exogenous phenolics, salinity, and their combination. In more detail, flavonoids, lignans, and stilbenes were the most affected phenolics, whereas glycosidase enzymes and tyrosinase activity were the most affected among enzyme assays. In conclusion, the exogenous application of phenolics to lettuce represents an effective and green strategy to effectively modulate the phenolic profile, antioxidant activity, and enzyme inhibitory effects in lettuce, deserving future application to produce functional plant-based foods in a sustainable way.

MicroRNA-based regulatory mechanisms underlying the synergistic antioxidant action of quercetin and catechin in H2O2-stimulated HepG2 cells: Roles of BACH1 in Nrf2-dependent pathways

The microRNA-based mechanisms underlying the antioxidant action(s) of co-existing flavonoids in response to oxidative stress are of high interest. This study aimed to extend the existing knowledge and provide insights into the potential regulatory network in response to oxidative stress and the co-presence of quercetin and catechin antioxidants, via a preclinical approach using H₂O₂-stimulated HepG2 cells. It was confirmed that BACH1 serves as an essential and direct negative regulator of the Keap1-Nrf2 signaling pathway and the antioxidant synergism between quercetin and catechin. BACH1 promoted reactive oxygen species (ROS) accumulation while inhibiting cell growth, which could be reversed by the synergistic action of let-7a-5p and miR-25-3p in the co-presence of quercetin and catechin. Both let-7a-5p and miR-25-3p could directly regulate the expression and function of BACH1 (e.g. upregulation of the two miRNAs could rescue largely overexpression of BACH1). Although these molecular interactions likely represented only some aspects of the overall regulatory network, this research confirms the feasibility of the combined uses of dietary flavonoids with chemopreventive properties in synergy during multiple-target interactions and multiple-pathway regulation.