The Anti-Bacterial Activity of Resveratrol Against a Group of Gram-Negative and Gram-Positive Bacteria

Resveratrol, a polyphenolic compound abundantly present in grape skins and seeds, is recognized for its antioxidant and antibacterial properties. Its capacity to inhibit microbial growth and interfere with essential cellular processes has made it a subject of increasing interest as a natural antimicrobial candidate. The study aimed to evaluate the antibacterial activity of grape-derived resveratrol against selected Gram-positive and Gram-negative bacterial species at different concentrations. Four bacterial species were tested: two Gram-positive (Bacillus subtilis and Staphylococcus aureus) and two Gram-negative (Escherichia coli and Salmonella typhimurium). Resveratrol solutions were prepared at concentrations of 25, 50, and 75 mg/ml. The antibacterial activity was assessed using the well-diffusion method on Mueller-Hinton Agar. Bacterial suspensions were standardized according to the McFarland method and incubated at 37 °C for 24 hours. Inhibition zone diameters were then measured. Resveratrol exhibited inhibitory effects against all tested bacterial strains, with varying levels of sensitivity. Bacillus subtilis showed the highest susceptibility (35 mm at 75 mg/ml), followed by Staphylococcus aureus (28 mm) and Escherichia coli (25.5 mm), while Salmonella typhimurium displayed the lowest sensitivity. Overall, resveratrol was more effective against Gram-positive bacteria than Gram-negative, likely due to the structural complexity of the Gram-negative cell wall and outer membrane, which restrict compound penetration.