Use of Quinoline Alkaloids as Markers of the Floral Origin of Chestnut Honey

To identify potential floral markers of chestnut honey, the phytochemicals present in chestnut floral nectar collected by bees were analyzed. Two nitrogen-containing compounds were detected, isolated, and identified as 4-hydroxyquinaldic acid (kynurenic acid) and 4-quinolone-2-carboxylic acid by H-1 NMR and C-13 NMR. In addition, chestnut nectar contained the monoterpene 4-(1-hydroxy-1-methylethyl)cyclohexa-1,3-diene-1-carboxylic acid, its gentiobioside ester, and the flavonol quercetin 3-pentosylhexoside, These nectar markers were found in different chestnut unifloral honey samples, although the flavonol was not detected in all samples analyzed. The terpenoid derivatives had previously been found in linden and tilia honeys. These results show that quinoline alkaloids are potentially good markers of chestnut honey, as they were not detected in any other unifloral honey analyzed so far. They are present at concentrations ranging from 34 to 65 mg/100 g of honey in the samples analyzed. In addition, the terpenoid and flavonoid derivatives present in nectar, although not exclusively characteristic of this floral origin, are good complementary markers for the determination of the floral origin of chestnut honey.