Biological Activity of Sour Cherry Fruit on the Bacterial Flora of Human Saliva in vitro

This study is the first report on the antibacterial effect of Hungarian sour cherry cultivars. Biological activity of sour cherry juices prepared from fruits Erdi jubileum, Erdi botermo, Maliga emleke and Kantorjanosi 3 harvested at different maturity stages was investigated on bacteria present in human saliva. The influence of sour cherry on a mixed bacterial flora of human saliva of 10 volunteers was determined by different experimental approaches. Bactericidal effects were evaluated by minimum inhibitory concentration (MIC) using agar diffusion methods and by minimum bactericidal dilution (MBD) assays counting the number of surviving bacterial cells in the diluted juices. Time-dependent antibacterial effects were also determined by monitoring the decrease in bacterial cell numbers after the treatment with undiluted juices. The investigated sour cherry juices displayed an impressive bactericidal effect against human saliva bacteria (10-100x reduction of cell numbers) within a short time frame (10-40 min). Erdi jubileum was more effective (100 000x reduction of cell number after 270 min) than the other studied cultivars. Bactericidal effect was influenced by ripening of samples of Erdi jubileum obtained at different harvesting dates. Biologically active components were effective against a large spectrum of opportunistic bacterial pathogens such as Pseudomonas, Klebsiella, Pantoea spp. and Escherichia coli, including the antibiotic-resistant Pseudomonas aeruginosa but they were ineffective against beneficial probiotic Lactobacillus spp. Results confirmed the antibacterial potential of all the investigated sour cherry fruits, therefore the consumption of the fruit or its juice for positive influence on oral hygiene is highly recommended.