Australian manuka honey is at least as powerful against bacteria as the more commonly known New Zealand variety, according to a new study published in the journal PLoS ONE.

A researcher with manuka honey in the lab. Image credit: Vanessa Valenzuela Davie.

Honey has been used therapeutically by many cultures for millennia and has re-emerged as a treatment for wound and skin infections, mainly due to its antimicrobial activity, the studys authors said.

Honey produced from Leptospermum scoparium (manuka) exhibits broad-spectrum antimicrobial activity against a diverse range of bacterial and yeast pathogens, and is equally effective against multi-drug resistant bacteria.

New Zealand is the primary source of medicinal honey but the country grows only one Leptospermum species, L. scoparium, and its honey bee population is threatened by the parasitic varroa mite.

Australia is home to 83 of the 87 known Leptospermum species and is still free of the varroa mite, unlike the rest of the beekeeping world.

Australia has more than 80 Leptospermum species, and limited research to date has found at least some produce honey with high non-peroxide antibacterial activity (NPA) similar to New Zealand manuka, the researchers said.

The activity of manuka honey is largely due to the presence of methylglyoxal, which is produced non-enzymatically from dihydroxyacetone present in manuka nectar.

The aims of the current study were to chemically quantify the compounds contributing to antibacterial activity in a collection of Australian Leptospermum honeys, to assess the relationship between methylglyoxal and NPA in these samples, and to determine whether NPA changes during honey storage.

The scientists examined 80 honey samples from New South Wales and Queensland flowering manuka trees and found that methylglyoxal is present in Australian varieties.

Eighty different Leptospermum honey samples were analyzed, and therapeutically useful NPA was seen in samples derived from species including L. liversidgei and L. polygalifolium, they said.

Exceptionally high levels of up to 1,100 mg of methylglyoxal per kg of honey were present in L. polygalifolium honey samples sourced from the Northern Rivers region in New South Wales and Byfield, Queensland, with considerable diversity among samples.

The study provides the proof for what weve long assumed — that methylglyoxal is present in high levels in Australian manuka honeys, said study lead author Dr. Nural Cokcetin, from the University of Technology Sydney.

Weve also shown that the activity of Australian manuka honeys has remained unchanged over seven years from harvest, which has huge implications for extending the shelf life of medicinal honey products.

These findings put Australian manuka honey on the international radar at a time when antibiotic resistance is recognized as a global crisis, Dr. Cokcetin said.

All honeys have different flavors and medicinal properties, depending on the flowers bees visit for nectar. What makes manuka honey so special is the exceptionally high level of stable antibacterial activity that arises from a naturally occurring compound in the nectar of manuka flowers. Its the ingredient we know acts against golden staph and other superbugs resistant to current antibiotics.

Honey not only kills bacteria on contact but we have shown previously that bacteria dont become resistant to honey, added co-author Prof. Liz Harry, also from the University of Technology Sydney.

That the manuka varieties in Australia are just as active as those in New Zealand, and have essentially the same chemical profile, will add significant value to Australian honey for beekeepers and provide a plentiful supply of medicinal honey.

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