Monitoring the antioxidant and antimicrobial power of grape (Vitis vinifera L.) stems phenolics over long-term storage

The wine industry involves the production of large quantities of by-products, characterized by a valuable composition in phytochemicals with putative health-promoting qualities. Additionally, in light of recently revealed multidrug-resistant bacteria framework, the search for natural antimicrobial compounds has focused its attention on these compounds as promising alternatives. In this study, grape stems were assessed on their phytochemical composition and antimicrobial activity throughout storage (64 days). Upon this characterization, stems were noticed as a valuable source of total phenols, ortho-diphenols and flavonoids (42.04-96.29 and 45.52-81.11 mg GA g(-1), and 29.46-76.20 mg CAT g(-1), respectively), and ABTS and DPPH radical scavenging capacity (4.28-8.56 and 0.46-1.00 mmol Trolox g(-1), respectively), which remained stable during storage. In addition, all polyphenolic extracts were competent in inhibiting the bacterial growth of selected Gram-positive and Gram-negative bacteria strains (% of relative inhibition zone diameter >= 47), being quite interesting to the food-pharma industries as functional ingredients.