Abstract
Background/Objectives: Wine pomace is a rich source of bioactive phenolic compounds with potential health benefits. This study aimed to evaluate the antipathogenic and antioxidant properties of ethanol and ethyl acetate extracts from wine pomace of three grape varietals (Tannat, Bonarda, and Malbec) to explore their potential as natural alternatives for mitigating bacterial virulence in Pseudomonas aeruginosa. Methods: Successive exhaustion extractions were performed using solvents of increasing polarity (ethyl acetate and ethanol). The phenolic content was quantified, and the antioxidant activity was evaluated using standard assays. The antipathogenic activity against P. aeruginosa was assessed by measuring biofilm formation, elastase and protease activity, pyocyanin production, and swarming motility. Quorum sensing (QS) inhibition was tested using a violacein production assay in Chromobacterium violaceum. Results: Ethanol was more effective at extracting phenolic compounds, with Tannat exhibiting the highest total phenolic content (162.5 µg GAE/mg). HPLC-DAD analysis identified 16 phenolic acids, 18 flavonoids, and 3 stilbenes across the extracts. The ethanol extracts showed strong antioxidant activity (phosphomolybdenum reducing capacity 67-128 μg AAE/mg, ABTS(•+) scavenging 37-71 µg/mL, Fe(3+) reducing power 31-68 µg/mL) and inhibited biofilm formation (up to 61%), elastase (up to 41%), and protease (up to 46%) activities in P. aeruginosa. The extracts also reduced pyocyanin production (up to 78%) and swarming motility (up to 68%), suggesting interference with QS. Moreover, the extracts inhibited violacein production in C. violaceum, confirming QS inhibition (up to 26%). Conclusions: Among the extracts, ethanol-extracted Tannat pomace showed the most substantial antipathogenic and antioxidant activities. The results add value to wine pomace by suggesting its use as natural extracts rich in phenolic compounds, capable of controlling the bacterial virulence of Pseudomonas aeruginosa without promoting the development of resistance.