MS Thesis Defense by Kyla Lockhart, Cranberry Leaf Extracts as a Tool Against Staphylcoccus aureus: Composition and Biofilm Inhibitory Properties
SENG 307B
Heather Blaser
508-999-8587
hblaser@umassd.edu
Title: Cranberry Leaf Extracts as a Tool Against Staphylcoccus aureus: Composition and Biofilm Inhibitory Properties by Kyla Lockhart
Advisor: Dr. Catherine Neto, Chemistry & Biochemistry Dept.
Committee Members: Dr. Shuowei Cai, Chemistry & Biochemistry Dept. & Dr. Frank Scarano, Medical Labratory Science
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 bacteria which forms biofilm by producing extracellular polysaccharide (EPS). This process allows these bacteria to spread and become harder to kill as the EPS 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-LH20 chromatography and LCMS and GCMS 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 EDII was the most effective, with inhibition of 88% and 78% respectively at a concentration of 12.5 µg/mL. EDII was found to contain isomers of the phenolic compound p-coumaroylquinic acid and was further separated into subfractions which were analyzed through LCMS and biological testing. The best result for biofilm inhibition was obtained for fraction F5 with 83% and the best biofilm eradication was obtained for fraction F4 with 68%. These fractions were found to contain 1-p-coumaroylquinic acid, 5-p-coumaroylquinic acid and chicoric acid which may contribute to their anti-bacterial and antioxidant effects. ED fractions and subfractions were also tested for antioxidant activity using the DPPH assay. Many of these fractions had promising free radical scavenging activity, with the the most promising results observed for fractions EDVI and EDVII and subfraction F5 which had IC50 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.