Native honey a sweet antibacterial

By Katherine Nightingale 3 March 2011
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Some potent varieties of Australian honey be used to treat superbugs, say researchers.

A NATIVE HONEY MAY well be the most powerfully antimicrobial honey ever discovered, say Queensland researchers.

The honey, cultivated at undisclosed locations in northern NSW and southeast Queensland, is made by bees that have fed on Leptospermum polygalifolium, also known as jelly bush or the lemon-scented tea tree.

The researchers tested 100 jelly bush honeys from a range of areas and found that some had 1750mg/kg of the antibacterial compound ‘methylglyoxal’ – the highest concentration yet found in this kind of honey. This is higher even than the concentration found in New Zealand’s famed manuka honey, made from Leptospermum scoparium, a cousin to the myrtle tree.

Honey has long been known to have antimicrobial properties, and has been used since ancient times as a remedy for wounds. Interest in its medicinal use has resurged in recent years with the discovery of the potency of manuka and jelly bush honeys.

Unknown x-factor

Jelly bush grows all along the east coast from southern NSW to Cape York, but no one knows why only certain trees lead to the highest methylglyoxal levels in honey, says Dr Yasmina Sultanbawa, with the Queensland Alliance for Agriculture and Food Innovation (QAAFI), which carried out the latest study with the University of Queensland and two medicinal honey companies.

An additional unknown is how methylglyoxal works, she says. All honey has antibacterial activity to a certain extent, but only honeys such as jelly bush and manuka have particularly strong antimicrobial and anti-inflammatory effects, and they also seem to hasten the wound-healing process.

What is known is that methylglyoxal’s antimicrobial potency is strengthened when it’s taken in honey, suggesting that it acts in synergy with other components – this is an area the researchers plan to further study. “We’re looking at the mechanism of action of methylglyoxal and also the other antimicrobial phytochemicals and enzymes in honey. This is just the tip of iceberg; there is a lot more to be done,” says Yasmina.

Promising superbug remedy

Medical-grade manuka and jelly bush honeys are already used in ointments and dressings. The latest high-methylglyoxal honeys, however, have shown some promise in laboratory tests against the ‘superbug’ Methicillin-resistant Staphlococcus aureus (MRSA), which has become resistant to common antibiotics, says Yasmina. The next step is to test it in people.

However, Dr Peter Molan, from the University of Waikato in New Zealand, argues that a higher methylglyoxal level doesn’t necessarily correlate with a better antimicrobial effect. Peter, a biochemist, discovered the antimicrobial activity of manuka honey in the 1980s and says the synergy that boosts methylglyoxal activity has been found only in some types of manuka honey.

On its own, methylglyoxal can kill some human cells as well as bacterial cells, but there is something in medical-grade manuka honey which counteracts this toxicity, says Peter. “With the Queensland honey, it is not known whether there is enough of the protective component to overcome the toxicity of the very high levels of methylglyoxal. A lot more testing would be required before it could be assumed to be safe to use on infected tissues,” he says.

QAAFI is a partnership between The University of Queensland and the Queensland Government’s Department of Employment, Economic Development and Innovation (DEEDI).