The escalating global concern over antimicrobial resistance has necessitated the search for alternative strategies to combat multidrug-resistant bacterial infections. Natural compounds, particularly those derived from plant sources, have emerged as promising alternatives to antibiotics. In this context, this study aimed to explore the antimicrobial potential of phenolic compounds extracted from winemaking by-products of Tinto Cão grapes against 10 multidrug-resistant bacterial strains. Additionally, the antioxidant activity of these compounds was evaluated.
Skin, seed, stem, shoat, and leaf sub-products from Tinto Cão grapes were extracted for their phenolic compounds. The antimicrobial activity was assessed against a panel of multidrug-resistant bacteria, including S. epidermidis, S. aureus, L. monocytogenes, E. faecium, E. faecalis, B. cereus, K. pneumoniae, P. aeruginosa, S. enteritidis and E. coli using MIC values. The antioxidant potential was measured using EC50 values obtained from DPPH, FRAP, and CuPRAC assays.
Among the bacterial strains tested, S. epidermidis, S. aureus, K. pneumoniae, P. aeruginosa, B. ceureus, and L. monocytogenes displayed susceptibility to the extracted phenolic compounds. The shoat extracts showed the highest antimicrobial activity, inhibiting six out of the ten bacterial strains and displaying lower MIC values ranging from 10 to 50 mg/mL. The lowest MIC value obtained was with the shoat extract against S. aureus, with a MIC of 10 mg/mL. Seed extracts demonstrated the highest antioxidant activity with the DPPH and CuPRAC methods (0.63±0.02 and 0.51±0.002, respectively), while leaf extracts exhibited the highest antioxidant activity with the FRAP method (0.55±0.001).
Our study showcases potent antimicrobial activity of phenolic compounds from Tinto Cão grape winemaking by-products against multidrug-resistant bacteria. These findings suggest their potential as a natural solution to combat antimicrobial resistance, promoting sustainable and effective strategies beyond traditional antibiotics.
