Phenolic profiles of Australian monofloral Eucalyptus, Corymbia, Macadamia and Lophostemon honeys via HPLC-DAD analysis

Abstract

Australian honey samples from four botanical genera (Lophostemon, Eucalyptus, Macadamia and Corymbia) were investigated for their phenolic content. An improved phenolic extraction and high-performance liquid chromatography-diode array detection (HPLC-DAD) analysis method allowed for the rapid and reliable identification of phenolic compounds. A concentrated liquid-liquid extraction method with an acidified aqueous solution and acetonitrile was optimised to isolate phenolic compounds from the honey matrix. The concentrated extraction method improved sensitivity and permitted the identification of phenolics present at low concentrations (LOD: 0.012–0.25 mg/kg and LOQ: 0.040–2.99 mg/kg). The optimised HPLC-DAD chromatographic conditions gave stable retention times, improved peak separation and allowed for the inexpensive detection of each of the 109 phenolic compounds at their maximum absorbance wavelength. Out of the 109 phenolic compounds included in this study, 49 were identified in the Australian honeys tested. Furthermore, 25 of the 49 compounds were determined to be markers specific to honey floral origin.