Fluorescence: A Novel Method for Determining Manuka Honey Floral Purity

Manuka honey, harvested from Leptospermum scoparium, is New Zealand\u27s most recognised honey type and commands a premium due to health‐related benefits. However, the plant\u27s distribution, relative to other species flowering simultaneously, allows honeybees to incorporate alternative nectars into the honey. Melissopalynological analysis in New Zealand is often unrepresentative due to the presence of many pollen‐bearing sources; consequently, alternative means of categorising manuka honey were examined. RP‐HPLC revealed that manuka honey contains distinct compounds, of which were relatively enriched and not present in the other New Zealand monofloral honeys. These main candidate compounds were isolated and have been described by mass spectrometry and nuclear magnetic resonance, synthesised to confirm structure, and as standards. These compounds, Leptosperin and Lepteridine, are a methyl syringate glycoside and pteridine derivative, respectively. Examination of these compounds revealed unique fluorescence signatures, this fluorescence could be detected in manuka honey samples the signal used to confirm that a honey was solely or predominantly consisted of L. scoparium nectar. Commercial manuka honeys were assessed by traditional analytical techniques, and comparisons were made with fluorescence signature; the fluorescence technique determined the authenticity of the honeys accurately