Antibacterial phenolic components of New Zealand manuka honey

This paper describes several methods for isolation of the antibacterially active phenolic fraction of honey derived from the native New Zealand manuka tree, Leptospermum scoparium (Myrtaceae). This fraction consists of phenolic derivatives of benzoic acids, cinnamic acids and flavonoids, all of which have been identified previously in honeys which do not exhibit non-peroxide residual antibacterial activity. The flavonoids had not previously been identified in manuka honey. Furthermore, the flavonoids were different from those found in the leaves of manuka trees but were the same as those found in European honeys and propolis. While most of these phenolic products possess antibiotic activity, they do not individually or collectively account for the antibacterial activity of `activeʹ manuka honey. Essentially all of this activity is associated with the carbohydrate fraction of the honey.