Considerable interest has emerged in developing biodegradable food packaging materials derived from polysaccharides. Phenolic compounds serve as natural bioactive substances with a range of functional properties. Various phenolic compounds have been incorporated into polysaccharide-based films and coatings for food packaging, thereby enhancing product shelf life by mitigating quality degradation due to oxidation and microbial growth. This review offers a comprehensive overview of the current state of polysaccharide-based active films and coatings enriched with phenolic compounds for preserving fruits and vegetables. The different approaches for the addition of phenols to polysaccharides-based packaging materials are discussed. The modifications in film properties resulting from incorporating polyphenols are systematically characterized. Then, the application of these composite materials as protectants and intelligent packaging in fruit and vegetables preservation is highlighted. In future, several points, such as the preservative mechanism, safety evaluation, and combination with other techniques along the whole supply chain could be considered to design polyphenol–polysaccharides packaging more in line with actual production needs.

Two lactic acid bacteria (LAB) strains of Lactobacillus plantarum 21802 and Lactobacillus brevis 6239 were selected and combined for fermentation of grape juice. The changes of sugars, organic acids, volatiles, phenolic compounds as well as antioxidant capacity of the grape juice were characterized. Results showed that fermentation with LAB led to a slight decrease in sugar content and increased in organic acid content. The sugars were mainly consumed at the initial stage of fermentation, while the malic acid was consumed completely during the fermentation. The contents of total phenolics and flavonoids in grape juice decreased gradually during the fermentation process. As compared with the initial contents in unfermented grape juice, the contents of proanthocyanin B2, rutin, isoquercitrin, rhamnose-3-O-glucoside in the final fermented grape juice were increased by 26.83%, 249.24%, 138.48%, 139.60%, respectively, while the contents of gallic acid, proanthocyanin B1, catechin and epicatechin were decreased by 24.49%, 14.85%, 71.68%, 42.52%, respectively. The mice fed with the fermented grape juice showed higher activity of superoxide dismutase and lower level of malondialdehyde both in serum and liver tissue than those fed with the unfermented grape juice. Fermentation with LAB also enhanced the flavor profile by increasing the total number and content of volatile compounds, especially those of monoterpene alcohols, which are the main and characteristic aroma volatile compounds in Muscat aroma grapes. This research confirmed that fermentation with LAB might be a desirable option for improving the flavor and nutritional attributes of grape juice by altering the ratio of sugar to organic acid, improving the phenolic compounds, enhancing the antioxidant capacity, intensifying of the characteristic aroma and pleasant flavor of the grape juice.

Epigallocatechin gallate (EGCG) and kaempferol exhibit cellular antioxidant activity; however, their interactive effects in terms of antioxidant actions and underlying mechanisms remain unclear. In this study, their cytoprotective effects were examined against 2,2-azobis (2-amidinopropane) dihydrochloride solution (ABAP)-induced oxidative stress in HepG2 cells. The results showed that the median effective dose (EC₅₀) of the EGCG and kaempferol (6:1.5, c/c) combination was 3.4 ± 0.1 μg/mL, with a combination index (CI_avg) value of 0.54, which represented a significant synergistic effect. Further experiments proved that the combined pretreatment with EGCG and kaempferol exerted protective effects by suppressing reactive oxygen species (ROS) generation, upregulating cellular antioxidant enzyme activities (superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px)) in a dose-dependent manner. The mechanism of synergistic antioxidant effects of EGCG combined with kaempferol may be due to the up-regulation of higher antioxidant enzyme activities that improve the antioxidant capacities and balance the cell oxidative stress. The synergistic antioxidant effect of EGCG and kaempferol can provide a theoretical basis for the development of formulas of functional food ingredients.

The search for safe, natural antimicrobial agents has received significant attention for controlling postharvest diseases in fruits. This study evaluated the antifungal activity of pomegranate peel extracts (PPE) against 9 pathogenic fungi by different methods. Additionally, the key antifungal polyphenol compounds were identified. Results revealed that the n-hexane partitioned fraction of ethanolic extract exhibited the highest inhibition efficacy. A total 36 polyphenols, including 10 newly discovered compounds in pomegranate peel were recognized. Among these, 9 specific polyphenols were found to be relatively abundant in the n-hexane fraction, highlighting their potential as primary antifungal agents. Notably, the newly identified polyphenol compound nobiletin demonstrated the strongest inhibitory effects against Colletotrichum gloeosporioides, Rhizopus stolonifer and Aspergillus niger with inhibition diameters of 12.2, 12.0, and 12.5 mm, respectively. Salidroside exhibited significant antifungal activity against Monilinia fructicola and A. niger (inhibition diameters > 12.0 mm). Furthermore, cinnamic acid that was enriched in hexane fraction, showed the highest inhibitory zones against Alternaria alternata, C. gloeosporioides and Botryosphaeria dothidea (11.8 ~ 12.7 mm). Caffeic acid and protocatechuic acid both displayed the lowest minimum inhibitory concentration (MIC) on Penicillium expansum. The study demonstrated the potential of PPE, particularly the n-hexane fraction, as a broad-spectrum natural antifungal agent for postharvest disease management.