Compositional analysis of Scottish honeys with antimicrobial activity against antibiotic-resistant bacteria reveals novel antimicrobial components

Antibiotic-resistant bacteria are a major health concern and honey may provide an alternative to antibiotic use under certain conditions. The antimicrobial action of six Scottish honeys and Manuka Medihoney((R)) was compared against antibiotic-resistant Acinetobacter calcoaceticus, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. Certain Scottish honeys, such as Highland and Portobello honey 2011, were comparable in effectiveness to the established antimicrobial Medihoney((R)), inhibiting growth to <1 compared to 10 log(10) CFU/ml in the control. Heather honey was the next most active while Blossom honeys were less active. Bacteria were inhibited by a sugar-matched control, but to a lesser extent, indicating that antimicrobial activity was associated with non-sugar components, such as poly-phenols. However, total phenol content or antioxidant capacity did not correlate with antimicrobial activity. Liquid chromatography-mass spectrometric analysis revealed that the composition of poly-phenol and non-polyphenol components differed between honeys. In addition, candidate components that could be associated with antimicrobial activity were noted including novel fatty diacid glycoside derivatives not previously identified in honeys. (C) 2017 Elsevier Ltd. All rights reserved.