New approach: Chemical and fluorescence profiling of NZ honeys. (30th November 2018) - Bong, Jessie
Highlights: NZ nectars and honeys screened for unique chemical constituents. Leptosperin, lepteridine, and 2-methoxyacetophenone only present in manuka nectar. Lumichrome only present in kanuka nectar. Optimal cut-off for unique compounds in manuka and kanuka honeys determined. Leptosperin and lepteridine fluoresce, allowing rapid screening of manuka honey authenticity. Abstract: 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 (94 mg/kg), lepteridine (2.1 mg/kg), 2′-methoxyacetophenone (2.0 mg/kg) for manuka honey, and lumichrome (4.5 mg/kg) for kanuka honey. The use of leptosperin and lepteridine as fluorescence markers for manuka honey authentication is reinforced.