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Proteomics is an emerging tool in food authentication that has not been optimised for honey analysis. In this study, we present a qualitative proteomic analysis of New Zealand mānuka (Leptospermum scoparium) honey. A total of fifty bee-derived proteins were identified in the honey, the most predominant being major royal jelly proteins (MRJPs). We also demonstrate for the first time the presence of unique nectar-derived proteins in mānuka honey. A total of 17 mānuka plant proteins were identified, a-third of which were putative pathogenesis-related proteins. Two proteins involved in drought tolerance were also identified. Twelve candidate peptides were selected as potential authentication markers based on their uniqueness to mānuka honey. Nectar analyses confirmed the origin and specificity of these peptides to L. scoparium nectar, thus presenting peptide profiling as a viable and novel approach for mānuka honey authentication. Raw data are available via ProteomeXchange with identifier PXD021730., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

New Zealand manuka (Leptospermum scoparium) and kanuka (Kunzea ericoides) honeys contain a unique array of chemical markers useful for chemical fingerprinting. We investigated the presence of 13 potential marker compounds in nectars of the major honey crop species. We confirmed that leptosperin, lepteridine, 2'-methoxyacetophenone, and 2-methoxybenzoic acid are exclusive to manuka nectar whereas lumichrome is unique to kanuka nectar. 3-Phenyllactic acid and 4-hydroxyphenyllactic acid are present in manuka and kanuka nectars. Leptosperin, lepteridine, 3-phenyllactic acid, and 4-hydroxyphenyllactic acid are chemically stable over prolonged storage, but not 2-methoxybenzoic acid and 2'-methoxyacetophenone. Accordingly, leptosperin and lepteridine are definitive chemical markers for authentication of manuka honey. An optimal concentration cut-off was established for the floral source-specific markers: leptosperin (94mg/kg), lepteridine (2.1mg/kg), 2'-methoxyacetophenone (2.0mg/kg) for manuka honey, and lumichrome (4.5mg/kg) for kanuka honey. The use of leptosperin and lepteridine as fluorescence markers for manuka honey authentication is reinforced., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The recent discovery of two unique manuka marker fluorescence wavelengths (MM1 and MM2) potentially offers a rapid and cost-effective approach for manuka honey authentication using spectroscopy. The fluorophore responsible for the MM1 marker has been identified as leptosperin. We investigated whether lepteridine may be responsible for the MM2 fluorescence. We quantified the lepteridine in manuka honey and manuka nectar, which ranged between 5-52mg/kg and 80-205mg/kg, respectively. Notably, the fluorescent spectrum of synthetic lepteridine matched the MM2 fluorescence signature. Fluorescence quenching was observed in the honey matrix but otherwise, lepteridine was stable over prolonged storage at 37°C. Lepteridine was also found in Australian Leptospermum honeys and nectars. Lepteridine concentration was positively correlated with concentrations of the MM1 fluorescence marker leptosperin in honeys. These findings identify lepteridine as the principle compound responsible for MM2 fluorescence, and support the utility as a marker compound for manuka honey authentication., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

New Zealand manuka (Leptospermum scoparium) honey exhibits two unique fluorescence signatures that distinguish it from other honey types. One of these is the MM1 fluorescence marker (270-365nm excitation-emission) which we show is due to a Leptospermum nectar-derived compound, leptosperin. Synthetic or honey-purified leptosperin not only displayed an identical fluorescence spectrum, but supplementation of leptosperin into clover or artificial honeys generated the MM1 fluorescence signature. There was a quenching effect of the honey matrix on leptosperin fluorescence but otherwise leptosperin was chemically stable over prolonged storage at 37°C. Leptosperin was also present in the woody-fruited Australian Leptospermum species at elevated concentrations but virtually absent in Leptospermum subtenue suggesting its elevated expression developed following the mid-Miocene separation of the genus. These findings suggest that fluorescence spectroscopy could offer a rapid and high-throughput screening method for identification of Leptospermum honeys using the MM1 fluorescence marker., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The fluorescence characteristics of various New Zealand honeys were investigated to establish if this technique might detect signatures unique to manuka (Leptospermum scoparium) and kanuka (Kunzea ericoides) honeys. We found unique fluorescence profiles for these honeys which distinguished them from other New Zealand honey floral types. Two excitation-emission (ex-em) marker wavelengths each for manuka and kanuka honeys were identified; manuka honey at 270-365 (MM1) and 330-470 (MM2) nm and kanuka honey at 275-305 (KM1) and 445-525 (KM2) nm. Dilution of manuka and kanuka honeys with other honey types that did not possess these fluorescence profiles resulted in a proportional reduction in fluorescence signal of the honeys at the marker wavelengths. By comparison, rewarewa (Knightia excelsa), kamahi (Weinmannia racemosa), and clover (Trifolium spp.) honeys did not exhibit unique fluorescence patterns. These findings suggests that a fluorescence-based screening approach has potential utility for determining the monoflorality status of manuka and kanuka honeys., (Copyright © 2015 Elsevier Ltd. All rights reserved.)