Antimicrobial Activity of Honeys

A total of 272 honeys have been sampled for antimicrobial activity since October 2001. These include honeys from coastal, forest, Goldfields, urban, exotic and overseas flora.

What makes honey antimicrobial?

There are two ways honey is considered antimicrobial – through hydrogen peroxide activity and non-peroxide activity. Honeys with non-peroxide activity only appear to come from Leptospermum plants such as Manuka and Jelly Bush.
Anti-microbial activity is cause by the strong interaction of honey sugars (fructose and glucose) with water molecules leaving very few water molecules available for micro-organisms. In addition the acidity (gluconic acid) of the honey derived from the ripening process from nectar is thought by some to provide anti-microbial activity. However, many researchers have found no correlation between acidity and antimicrobial activity.

What causes Hydrogen peroxide (H202) activity?

HA is formed when the enzyme glucose oxidase, found in the hypopharyngeal glands of honey bees, reacts with glucose. The enzyme is practically inactive in full strength honey and only gives rise to hydrogen peroxide when the honey is diluted. Its Inactivity in undiluted honey is probably due to the unfavourable p1-1 in ripened honey.
The bactericidal action of hydrogen peroxide can be enhanced by the presence of ascorbic acid (vitamin C), copper, iron, chromium, cobalt or manganese. Its level varies with floral source and can be reduced by feeding sugar to bees.

What causes non-peroxide activity?

Phenolics (types of acid) and oils in honey such as terpenes are likely to be responsible. Researchers have detected activity in the urine of people after they had consumed 50g honey. They found that maximum activity occurred 3 hours after consumption.