Polyphenol-rich extracts derived from agricultural by-products exhibit promising antiviral properties. This study evaluated the antiviral potential of extracts from red onion peels, vineyard prunings, olive prunings and chicory leaves against human coronavirus HuCoV-229E. Subcritical water extraction and resin adsorption techniques were applied to produce the extracts. The extracts were further characterised for their bioactive content, and three out of four extracts showed a high polyphenol content (>200 mg/g). The antiviral activity was assessed through viral infectivity and replication inhibition assays in human MRC-5 host cells. The results indicate that chicory leaf and red onion peel extracts demonstrated significant antiviral effects, with effective concentrations (EC₅₀) of 61.43 µg/mL and 10.1 µg/mL, respectively. Olive pruning extract exhibited moderate activity, while vineyard pruning extract showed limited efficacy. These findings suggest that polyphenol-rich agricultural by-products could serve as sustainable sources for antiviral agents, warranting further investigation into their mechanisms of action and potential applications against other coronaviruses, including SARS-CoV-2.

This study explores the development of functional fermented beverages using fibre-rich residues derived from olive pruning, vineyard pruning, chicory root, and red onion, obtained after subcritical water extraction of polyphenols. Two microbial strains, Lactiplantibacillus plantarum and Bacillus subtilis, were evaluated for their fermentation performance across different fibre matrices, with and without sugar supplementation. Key parameters including microbial growth, pH evolution, and reducing sugar content were monitored, and Lactiplantibacillus plantarum showed superior acidification and viability (>9 log CFU/mL), especially in sugar-enriched formulations, while Bacillus subtilis showed a limited performance. Based on fermentation efficiency, three sugar-supplemented formulations were selected to scale-up: olive pruning fibre and vineyard pruning fibre fermented with Lactiplantibacillus plantarum and olive pruning fibre fermented with Bacillus subtilis. Red onion fibre extract was excluded from scale-up experiments due to its high viscosity, which made it impossible to measure reducing sugars, consistent with its high water-holding capacity. Fermentation significantly increased antioxidant capacity, reaching up to 750 µmol Trolox equivalents/L and 18 mg of gallic acid equivalents/L in L. plantarum-fermented samples, confirming microbial release of bound phenolics and formation of bioactive metabolites. The resulting beverages were microbiologically stable (final pH < 4.5), sensorially acceptable, and potentially antioxidant-rich, supporting their role in sustainable food system development and circular bioeconomy.

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.