The rapid evaporative ionisation mass spectrometry metabolite fingerprint of Leptospermum honey is strongly associated with geographic origin

There is debate about whether the honey from Leptospermum scoparium nectar in New Zealand is substantially different to honey from Leptospermum spp nectar from Australia; many Leptospermum honeys have high amounts of the antibacterial compound methylglyoxal (MGO) but are known to differ in their amounts of other metabolites. Retail honey samples labelled as ‘mānuka’, manuka, or ‘tea tree’ honey sourced from New Zealand (n = 34) and Australia (n = 35), were measured using laser assisted-rapid evaporative ionisation mass spectrometry (REIMS) in positive and negative ionisation modes, with 1637 and 1744 molecular features detected, respectively. Country of origin was strongly reflected in the REIMS fingerprints irrespective of similarity of methylglyoxal, with >50% of detected features differing between New Zealand and Australian-sourced honey. Combined REIMS features in negative ionisation mode correlated strongly with current molecular markers of mānuka honey quality (r 2 > 0.9). Leptospermum honey from New Zealand and Australia have distinct molecular fingerprints, potentially due to evolutionary and genomic differences between the predominant Leptospermum species, bees, environment and honey processing.