FLORAL NECTAR PHENOLICS AS BIOCHEMICAL MARKERS FOR THE BOTANICAL ORIGIN OF HEATHER HONEY

In order to find out biochemical markers for the botanical origin of h eather (EI ica) honey, the phenolic metabolites present in heather flo ral nectar: collected from the honey-stomach of bees gathering nectar from these flowers, were analysed. The flavonoid fraction of nectar co ntained four main flavonoids. Two of them were quercetin and kaempfero l 3-rhamnosides, and the other two were tentatively identified as myri cetin 3'-methyl ether and isorhamnetin 3-rhamnosides. Since the natura l glycosides are hydrolysed by bee enzymes to render the corresponding aglycones, which are the metabolites detected in honey, acid hydrolys is of the nectar glycosides was achieved. The aglycones quercetin, myr icetin 3'-methyl ether, kaempferol and isorhamnetin were identified. a s well as the gallic acid derivative ellagic acid. The analysis of Por tuguese heather honey samples showed that ellagic acid was present in all the samples in significant amounts ranging between 100 mu g and 60 0 mu g per 100 g honey. The other nectar-derived flavonoids were also present, although some of them in very variable amounts. Ellagic acid and myricetin 3'-methyl ether, which have not been detected in any of the monofloral honey samples investigated so far, with the only except ion being a French honey sample of the botanically related Calluna (Er icaceae) which also contained ellagic acid, seem to be the most useful potential markers for the floral origin of heather honey. However, mo re detailed and extensive investigations are needed to prove the utili ty of these markers.