Fluorescent Pteridine Derivatives as New Markers for the Characterization of Genuine Monofloral New Zealand Manuka (Leptospermum scoparium) Honey

Abstract

New Zealand manuka honey is well-known for its unique antibacterial activity. Due to its high price and limited availability, this honey is often subject to honey fraud. Two pteridine derivatives, 3,6,7-trimethyl-2,4(1H,3H)-pteridinedione and 6,7-dimethyl-2,4(1H,3H)-pteridinedione, have now been identified in New Zealand manuka honey. Their structures were elucidated by LC-QTOF-HRMS, NMR, and single-crystal X-ray diffraction after isolation via semipreparative HPLC. Their marker potential for authentic manuka honey was proved as both substances were detectable in neither the pollen-identical kanuka honey nor the nine other kinds of monofloral New Zealand honey analyzed (clover, forest, kamahi, pohutukawa, rata, rewarewa, tawari, thyme, and vipers bugloss). The fluorescence property of the pteridine derivatives can be used as an easy and fast TLC screening method for the authentication of genuine manuka honey. 6,7-Dimethyl-2,4(1H,3H)-pteridinedione has been described for the first time.

HPTLC Fingerprinting—Rapid Method for the Differentiation of Honeys of Different Botanical Origin Based on the Composition of the Lipophilic Fractions

“…Spectroscopic methods such as NMR, FT-IR and NIR have also been successfully used for metabolomic studies [ 16 , 24 , 25 , 26 ]. There are limited reports about the usage of HPTLC [ 27 , 28 ], capillary electrophoresis [ 29 ], amperometric methods [ 30 ], ion chromatography [ 31 ] and even immunoassays [ 32 ]. Of course, the obtained results (including profiles and metabolomes) are strongly dependent on the isolation technique used to obtain the honey fraction and on the methods used to determine its composition.…”

In vivo absorption and metabolism of leptosperin and methyl syringate, abundantly present in manuka honey

“…Specific components of manuka honey could be used to verify the authenticity of the honey [8][9][10][11][12][13]. Our group has identified leptosperin and MSYR as inhibitors of an inflammatory enzyme, myeloperoxidase [14] and found that leptosperin is a characteristic compound exclusively found in Leptospermum honey [9].…”

Naturally Occurring Lumazines

“…31 Speer et al reported the replication of this isolation, along with 6,7-dimethyllumazine (9); the structures of both compounds were assigned using Xray crystallography. 32 New Zealand ma ̅ nuka honey is well known for its antibacterial activity and, as a result of its high cost and limited availability, is often the subject of honey fraud. 33 Lepteridine (8) exhibits fluorescence that is only detectable in ma ̅ nuka honey samples and has been put forward as a unique biomarker for the authentication of ma ̅ nuka honey.…”