Unique fluorescence and high-molecular weight characteristics of protein isolates from manuka honey ( Leptospermum scoparium )

Formation of Protein-Bound Maillard Reaction Products during the Storage of Manuka Honey

Honey from the nectar of the Manuka tree (Leptospermum scoparium) grown in New Zealand contains high amounts of antibacterial methylglyoxal (MGO). MGO can react with proteins to form peptide-bound Maillard reaction products (MRPs) such as Nε-carboxyethyllysine (CEL) and "methylglyoxal-derived hydroimidazolone 1" (MG-H1). To study the reactions of MGO with honey proteins during storage, three manuka honeys with varying amounts of MGO and a kanuka honey (Kunzea ericoides) spiked with various MGO concentrations up to 700 mg/kg have been stored at 37 °C for 10 weeks, and the formation of protein-bound MRPs has been analyzed via high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS) following isolation of the protein fraction and enzymatic hydrolysis. During storage, contents of protein-bound CEL and MG-H1 increased continuously, directly depending on the MGO content. For honeys with large amounts of MGO, a slower formation of Nε-fructosyllysine (FL) was observed, indicating competing reactions of glucose and MGO with lysine. Furthermore, the lysine modification increased with storage independently from the MGO concentration. Up to 58-61% of the observed lysine modification was explainable with the formation of CEL and FL, indicating that other reactions, most likely the formation of Heyns products from lysine and fructose, may play an important role. Our results can contribute to the authentication of manuka honey.

Fluorescent characteristics of bee honey constituents: A brief review

The eligible articles were obtained from databases such as ScienceDirect, SciELO, PubMed and Springer. The searches were performed using the terms "honey", "vitamins", "fluorescence" and their combinations. The titles and abstracts of the articles found were read and revised to verify their relevance to the review. From the selected titles, it was possible to elaborate the systematic review, based on scientific studies and sources considered faithful and true. The systematic review presented confirms the necessity for studies to identify compounds using fluorescence techniques, using cheaper and more accessible techniques. Few studies are covered in this theme, when treated about Apis mellifera honey, and it has been observed that in the last 12 years, the few researches have only tried to show the viability of using the technique without quantifying the present compounds, while others demonstrate the fluorescent aspects, but performing through techniques considered more expensive.