Abstract
Biofilm is a community of micro-organisms which forms as a means of protection. This community helps to protect the bacteria from its environment and to adhere to different surfaces. Staphylococcus aureus is a common gram-positive bacterial pathogen which forms biofilm by producing extracellular polysaccharide substances. This process allows these bacteria to spread and become harder to kill as the extracellular polysaccharide substances makes it more resistant to antibiotics. Cranberries are known for their antibacterial effects due to the proanthocyanidins (PACs) they contain. While there has been much research on the cranberry fruit, there is less known about the chemistry and antibacterial properties of the cranberry leaves. Through bioassay-guided fractionation of leaf extracts using Sephadex-lipophilic hydrophilic 20 chromatography and liquid chromatography mass spectrometry and gas chromatography mass spectrometry analysis we were able to characterize cranberry leaf fractions and observe their anti-biofilm effects on S. aureus. In the biofilm formation and eradication assays, fraction Early Black fraction II was the most effective, with inhibition of 88% and 78% respectively at a concentration of 12.5 µg/mL. Early Black fraction II was found to contain isomers of the phenolic compound p-coumaroylquinic acid and was further separated into subfractions which were analyzed through liquid chromatography mass spectrometry and biological testing. The best result for biofilm inhibition was obtained for subfraction 5 with 83% and the best biofilm eradication was obtained for subfraction 4 with 68%. These fractions were found to contain 1-pcoumaroylquinic acid, 5-p-coumaroylquinic acid and chicoric acid which may contribute to their anti-bacterial and antioxidant effects. Early Black fractions and subfractions were also tested for antioxidant activity using the 2,2-diphenyl-1-picrylhydrazyl assay. Many of these fractions had promising free radical scavenging activity, with the most promising results observed for fractions Early Black fractions VI and VII and subfraction 5 which had inhibitory concentration 50 values of 3.64, 1.21, and 17.7 µg/mL respectively. Overall, these findings demonstrate that cranberry leaves contain strong anti-biofilm and antioxidant properties which suggests they have potential as a natural antimicrobial source and sets the foundation for future studies in isolation and characterization of active compounds and their activity.