Screening of antibacterial activity of raspberry (Rubus idaeus L.) fruit and pomace extracts

Antibacterial activity of fruit and pomace extracts (concentration 50 mg/ml) of two raspberry (Rubus idaeus L.) cultivars (Meeker and Willamette) was tested against selected Gram-positive and Gram-negative bacteria (reference and wild strains). Disc diffusion method with 15 μl of extracts and agar-well diffusion method with 50 and 100 μl were used. Antibiotic (cefotaxime/clavulanic acid) was used as a control. Both raspberry fruit extracts showed the strongest antibacterial activity against Pseudomonas aeruginosa (wild strain) and Bacillus cereus, where the largest clear zones (without growth) appeared. Escherichia coli was the most resistant strain, with only zone of reduced growth. The highest antibacterial activity of pomace extracts was against Staphylococcus aureus and Staphylococcus saprophyticus. There were no differences in the antibacterial activity between cultivars for both fruit and pomace extracts. [Projekat Ministarstva nauke Republike Srbije, br. TR 31044]