ABSTRACT
This study is the first large-scale survey of the presence of dihydroxyacetone (DHA) in the nectar of the Australian Leptospermum tree species. The work undertaken supports the growing global demand for bioactive Leptospermum honey. Leptospermum honey derived from L. scoparium in New Zealand, also referred to as MaÌ nuka honey, has a reputation for wound-healing and antimicrobial properties, which is based on its methylglyoxal (MGO) content. High-DHA nectar correlates to high-MGO honey, but not all Leptospermum species produce DHA in their nectar. This study investigates 55 of the 84 Leptospermum species native to Australia for their DHA-producing capability, with the DHA to total sugar (DHA:Tsugar) ratio of nectar samples determined by HPLC-PDA. DHA:Tsugar ranged from nondetectable in L. laevigatum, L. coriaceum, and L. trinervium to >16â¯000 mg/kg in L. speciosum and L. whitei. High-DHA Leptospermum species were identified for beekeepers to target for honey production and plantation development.
Subject(s)
Dihydroxyacetone/chemistry , Leptospermum/chemistry , Plant Nectar/chemistry , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/therapeutic use , Australia , Dihydroxyacetone/therapeutic use , Honey , Humans , Pyruvaldehyde/chemistry , Species Specificity , Sugars/chemistry , Wound Healing/drug effectsABSTRACT
A reliable determination of dihydroxyacetone, methylglyoxal and 5-hydroxymethylfurfural is essential to establishing the commercial value and antimicrobial potential of honeys derived from the Leptospermum species endemic to Australia and New Zealand. We report a robust method for quantitation of all three compounds in a single HPLC run. Honey samples (n = 6) that are derivatized with o-(2,3,4,5,6-Pentafluorobenzyl) hydroxylamine were quantitated against a stable anisole internal standard. Linear regression analysis was performed using calibration standards for each compound (n = 6) and results indicated a high degree of accuracy (R2 = 0.999) for this method. The reliability of some commercial methylglyoxal solutions were found to be questionable. Effective quantitation of methylglyoxal content in honey is critical for researchers and industry, and the use of some commercial standards may bias data. Two accurate methylglyoxal standards are proposed, including a commercial standard and a derivative that can be prepared within the laboratory.
Subject(s)
Chromatography, High Pressure Liquid , Dihydroxyacetone/chemistry , Furaldehyde/analogs & derivatives , Honey/analysis , Leptospermum/chemistry , Chromatography, High Pressure Liquid/methods , Furaldehyde/chemistry , Reproducibility of ResultsABSTRACT
The nonperoxide antibacterial activity of New Zealand maÌ nuka honey originates from dihydroxyacetone (DHA) within Leptospermum scoparium nectar. This study determined if DHA was present within the nectar of four Australian Leptospermum species: L. laevigatum, L. polygalifolium, L. trinervium, and L. whitei. A rapid and convenient new method was developed, which quantitated DHA/sugar ratios (ppm). The DHA and sugars were derivatized with o-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine hydrochloride and analyzed via RP-HPLC with diode array detection at two wavelengths (200 and 243 nm). DHA was detected in all L. whitei and L. polygalifolium samples, where DHA/sugar ratios ranged from 10169 to 24199 ppm and from 9321 to 20174 ppm, respectively. DHA was undetected in any of the L. laevigatum and L. trinervium samples, and nectar activity was <100 ppm. The results of this study have implications for the Australian beekeeping industry, as the findings indicated that not all species of Leptospermum will produce active honey.
