7
NEW ZEALAND BEEKEEPER, JULY 2017
LEPTOSPERIN: A CHEMICAL MARKER BEING USED TO AUTHENTICATE MANUKA HONEY RESEARCH Steve Howse, Executive Director, Analytica Laboratories
This article gives a brief overview of the background to the discovery of leptosperin and why it is useful for authenticating mānuka honey.
Overview Leptosperin is a naturally occurring chemical compound found in mānuka nectar, which makes its way into honey made from that nectar. It is sometimes referred to as a ‘chemical marker’ for mānuka honey, with higher amounts of leptosperin in a honey indicating that a higher amount of mānuka nectar has been used to make the honey. Testing is able to be carried out quickly and inexpensively by laboratories, along with the other tests normally carried out in mānuka honey. Leptosperin is not included in MPI’s proposed group of mānukamarkers. It is used by the Unique Manuka Factor™ Honey Association (UMFHA) as a part of the UMF™ grading system, and they require any honey labelled with a UMF™ grade to contain at least 100 mg/kg of leptosperin. Leptosperin was first discovered by the Japanese researcher Yoji Kato The first scientific work on mānuka honey was carried out by the late Professor Peter Molan of the University of Waikato. This research focused on mānuka honey’s function, particularly non-peroxide activity (NPA). Over time, it was found that the NPA in mānuka honey was closely linked to the naturally occurring chemical compound methylglyoxal (MG), and later that MG in mānuka honey was formed from another naturally occurring chemical, dihydroxyacetone (DHA), which came from mānuka nectar. Focus then turned to identifying other unique chemical compounds found in mānuka honey. In 2014, a Japanese research team led by Professor Yoji Kato announced (and patented) the discovery of leptosperin—a
Figure 1: Chemical structure of leptosperin.
with the DHA or MG concentration in honey. This means you can’t use a leptosperin test result as an alternative to these for working out the grade of the honey, but despite this, it can be used as an indicator of the amount of mānuka nectar in the honey. Figure 2 shows the average concentration of leptosperin found in the nectar of some of the more common plants used for honey production in New Zealand, arising from UMFHA research carried out in 2013/2014. You can see that while there is no evidence of leptosperin in species like kānuka, kāmahi, and rewarewa (among others), it is found in mānuka. Australian research has shown that leptosperin is also found in the nectar of some Leptospermum species which grow in Australia. In general, if honey is from New Zealand and if there is enough leptosperin in it, you can be confident that it is mānuka honey.
naturally occurring chemical compound found in mānuka honey but not in other types of New Zealand honey (Kato, Fujinaka, Ishisaka, Nitta, Kitamoto, & Takimoto, 2014). This was confirmed soon after by the UMFHA-driven Mānuka ID project, and has been agreed with since then by other international researchers. Leptosperin is a complex chemical compound (Figure 1) that has been shown to be found in mānuka nectar, and makes its way into mānuka honey via the nectar collected by bees. Leptosperin is not a reactive compound, and therefore its concentration remains fairly stable over time. An incubation experiment carried out by Analytica, where honey was stored at 20°C and 27°C over nearly three years, showed that leptosperin concentrations reduced by less than 5% per year. Leptosperin concentration in mānuka nectar does naturally vary between plants and regions, and is not always directly correlated
continued...
Made with FlippingBook - Online magazine maker