Cornflower (Centaurea cyanus L.) honey quality parameters: chromatographic fingerprints, chemical biomarkers, antioxidant capacity and others

The samples of cornflower (Centaurea cyanus L.) honey from Poland were subjected to ultrasonic solvent extraction applying the mixture of pentane and diethyl ether 1:2 v/v (solvent A) as well as dichloromethane (solvent B). The major compounds of the extracts (analysed by GC–MS/GC–FID) were C13 and C9 norisoprenoids. Among them, (E)-3-oxo-retro-a-ionol (2.4–23.9% (solvent A); 3.9–14.4% (solvent B)) and (Z)-3-oxo-retro-a-ionol (3.7–29.9% (solvent A); 8.4–20.4% (solvent B)) were found to be useful as chemical biomarkers of this honey. Other abundant compounds were: methyl syringate (0.0–31.4% (solvent A); 0.0–25.4% (solvent B)) and 3-hydroxy-4-phenylbutan-2-one (1.6–15.8% (solvent A); 5.1–15.1% (solvent B)). HPLC–DAD analysis of the samples revealed lumichrome (4.7–10.0 mg/kg), riboflavin (1.9–2.7 mg/kg) and phenyllactic acid (112.1–250.5 mg/kg) as typical compounds for this honey type. Antioxidant and antiradical properties as well as total phenolic content of the samples were found to be rather moderate by FRAP (ferric reducing antioxidant power), DPPH (1,1-diphenyl-2-picrylhydrazyl radical) and Folin–Ciocalteu assays, respectively. Additionally, CIE L⁄a⁄b⁄C⁄h chromatic coordinates were evaluated. Colour attributes of cornflower honey were characterised by elevated values of L* and particularly high values of b* and h coordinates, which correspond to medium bright honey with intense yellow colour.