Manuka honey is a New Zealand bee honey, which has long been used in traditional medicine in New Zealand and in recent years is increasingly finding its way into traditional medicine. Especially the special antibacterial effect makes Manuka honey so unique and sets it apart from other honeys.
What is so special about Manuka honey?
Manuka honey combines the special features of the Manuka tree and the good properties of honey. In general, honey is said to have a health-promoting and partially germicidal effect. In this regard, the high sugar concentration of honey is said to extract water from germs, causing them to die. Likewise the low pH value of honey represents an acid environment unsuitable for bacteria. In addition, honey contains the enzyme glucose oxidase, which forms hydrogen peroxide. Hydrogen peroxide has a disinfecting effect. However, it is disputed whether honey in this way is actually sufficiently germicidal for medical use.
Antibacterial effect of Manuka honey
The antibacterial effect of Manuka honey, on the other hand, is well recognized. Researchers discovered that a particular substance, methylglyoxal (MGO), is responsible for the antibacterial effect.5, 6 Manuka honey, unlike other honey, contains considerable amounts of methylglyoxal, making manuka honey a highly medicinal agent.
The antibacterial action of methylglyoxal is referred to as non-peroxidic activity (NPA) to distinguish it from the modes of action of conventional honey. But methylglyoxal is not the only antibacterial agent in Manuka honey. Flavonoids and phenolic acids are also considered antibacterial substances. Thus, Manuka honey offers several approaches to successfully fight bacteria. This makes it more difficult for bacteria to adapt to Manuka honey and form resistances. This could be a key advantage of Manuka honey over synthetic antibiotics.
The production of Manuka honey
Honey bees of the species Apis mellifera produce manuka honey by collecting the nectar of the South Sea myrtle and processing it into honey. The scientific name of the South Sea Myrtle is Leptospermum scoparium. However, it is also called the Manuka tree, the word “Manuka” being derived from the Maori language. Kahikatoa is another Maori name for the South Sea Myrtle. South Sea Myrtle can grow as a tree or shrub and blooms from December to February with white or pink flowers.
Busy bees do most of the work
Bees achieve the processing of nectar into honey essentially by breaking down starch into glucose (grape sugar) and fructose (fruit sugar) and by extracting water. The bees themselves manage the thickening process to such an extent that the immature honey only has a water content of about 40 percent. The bees then transfer the immature honey to the honeycombs of the beehive, where it loses further water through evaporation. The bees actively support evaporation through wing beating, ventilation and temperature regulation. Ripe honey should have a water content of less than 20 percent to protect it from fermentation processes. Ideally, the water content of Manuka honey is between 16 and 18 percent.
Bacteria are important for the MGO content
In addition, bacteria that live in the bees serve a special purpose in the ripening of the honey. On the one hand, they are responsible for the pH of the honey, and on the other hand, they produce a metabolic breakdown product that becomes methylglyoxal through subsequent dehydration. Together with the immature honey, the bacteria are transported by the bees into the honeycombs, where they complete their work.
As the honey matures, more and more bacteria die as the decreasing water content and increasing MGO content make it difficult for them to survive. The nectar of Manuka flowers contains particularly high levels of the starting material, which is converted to methylglyoxal with the help of the bacteria and subsequent dehydration. Only Manuka honey is therefore rich in methylglyoxal.
When the honey is ripe, the bees close the combs with a wax lid. Then it is time for beekeepers to harvest the honey. The beekeepers remove the wax lids and use a special centrifuge to spin the honey out of the combs. They then filter the honey before it is bottled and ready for sale.
What does UMF and MGO mean?
To better classify the antibacterial effect of Manuka honey, the “unique manuka factor” (UMF) was created. The UMF is directly related to the MGO content. Finally, methylglyoxal is considered to be the antibacterial active ingredient of manuka honey.
However, the UMF value is older than the knowledge of methylglyoxal. Therefore, according to the original method, the UMF value can be determined independently of the MGO content. For this purpose, bacterial cultures are used to test how anti-bacterial the honey samples actually are. The effect obtained is then compared with the effect of a so-called phenol solution.
Phenol solutions were previously used as disinfectants and it is known how strong an anti-bacterial effect a phenol solution has at a certain concentration. The number given after the UMF value therefore corresponds to the concentration of a phenolic solution with a correspondingly strong anti-bacterial effect. For example, a Manuka honey with a UMF value of 10 has a comparably strong anti-bacterial effect as a 10 percent phenol solution.
However, UMF also serves as a registered seal of quality. It is controlled by the independent New Zealand UMF Honey Association and guarantees the authenticity of the New Zealand Manuka Honey and the stated UMF value. A + after the UMF value means that the MGO content is higher than the stated UMF value, but lower than the MGO content of the next UMF level. In addition, the UMF value is also directly related to the antioxidant effect of manuka honey and the content of phenolic compounds, as scientists from Northern Ireland found out in 2015.