PLANT PHENOLIC METABOLITES AND FLORAL ORIGIN OF ROSEMARY HONEY

Phenolic metabolites present in rosemary honey and floral nectar were studied to find biochemical markers for honey floral origin. Rosemary nectar, from bee honey stomach, contained kaempferol 3-sophoroside (93%) and quercetin 3-sophoroside (7%) as the only significant constituents. All samples had a common flavonoid profile comprised of 15 flavonoids. Nectar glycosides were not detected in honey suggesting that they are hydrolyzed by the bee enzymes to render the corresponding aglycons. Honey flavonoid profiles were similar to those found for propolis, a plant resin collected by bees, and confirmed that the majority of the flavonoids present in honey originate from this source. The amount of kaempferol in the honey samples ranged between 0.4 and 1.2 mu g/g. The coefficient of variation of kaempferol in the honey samples was much smaller than those observed for the rest of flavonoids, supporting its floral origin, and the propolis origin for the rest of flavonoids. The presence of kaempferol in rosemary honey cannot be considered as proof of its floral origin because this flavonol can originate from different flower nectars. However, its absence or presence in small levels (< 0.3 mu g/g of honey) could be considered additional evidence of a different floral origin.