Natural Occurrence of Abscisic Acid in Heather Honey and Floral Nectar

HPLC analysis of Portuguese heather honey (Erica spp.) fractions revealed that two non-flavonoid compounds were the main constituents, while flavonoids and other phenolic metabolites were only present as minor constituents. These two substances were isolated and identified as cis,trans-abscisic acid and trans,trans-abscisic acid by EIMS, 1H NMR, and 13C NMR techniques. Their content ranged between 2.5 and 16.6 mg/100 g of honey. When Erica flower nectar was analyzed, both isomers were also observed as the main constituents and confirmed the floral origin of the compounds found in honey. These were not detected in any of the different monofloral honey samples analyzed so far and, therefore, could be useful markers of heather honey. More heather samples from other geographical and botanical (Erica spp., Calluna spp., etc.) origins should be analyzed in order to prove that abscisic acid could be a useful floral marker of heather honey. Keywords: Abscisic acid; honey; heather; Erica; nectar; characterization