Analytical method development using FTIR-ATR and FT-Raman spectroscopy to assay fructose, sucrose, glucose and dihydroxyacetone, in Leptospermum scoparium nectar

The carbohydrate dihydroxyacteone (DHA) occurs in significant levels in Leptospermum scoparium (mānuka) nectar and is the precursor of methylglyoxyl (MGO), the unique non-peroxide antibacterial activity (NPA) component in mānuka honey. The nectar of ten different cultivars of L. scoparium was assayed quantitatively for fructose, glucose, sucrose, and DHA with high pressure liquid chromatography (HPLC) for comparison with FT-Raman and FTIR-ATR spectroscopic methods. FT-Raman spectroscopy and ATR-FTIR spectroscopy, alongside chemometric methods using principal component analysis (PCA) and partial least squares (PLS) prediction were shown to be useful techniques to quantify and compare the nectar composition in a range of cultivars of L. scoparium.