Nectar Flavonol Rhamnosides Are Floral Markers of Acacia (Robinia pseudacacia) Honey

Abstract

With the objective of finding floral markers for the determination of the botanical origin of acacia (robinia) honey, the phytochemicals present in nectar collected from Robinia pseudacacia flowers were analyzed by high-performance liquid chromatography-tandem mass spectrometry. Eight flavonoid glycosides were detected and characterized as kaempferol combinations with rhamnose and hexose. Acacia honey produced in the same location where the nectar was collected contained nectar-derived kaempferol rhamnosides. This is the first time that flavonoid glycosides have been found as honey constituents. Differences in the stability of nectar flavonoids during honey elaboration and ripening in the hive were shown to be due to hydrolytic enzymatic activity and to oxidation probably related to hydrogen peroxide (glucose-oxidase) activity. Acacia honeys contained propolis-derived flavonoid aglycones (468-4348 microg/100 g) and hydroxycinnamic acid derivatives (281-3249 microg/100 g). In addition, nectar-derived kaempferol glycosides were detected in all of the acacia honey samples analyzed (100-800 microg/100 g). These flavonoids were not detected in any of the different honey samples analyzed previously from different floral origins other than acacia. Finding flavonoid glycosides in honey related to floral origin is particularly relevant as it considerably enlarges the number of possible suitable markers to be used for the determination of the floral origin of honeys.

The Value of Chilean Honey: Floral Origin Related to their Antioxidant and Antibacterial activities

“…A signiicant decrease in the concentration of galangin, kaempferol, myricetin, and þ-coumaric acid was observed after heat treatment [23]. Moreover, some lavonoid glycosides present in honey demonstrate certain instability under slight alkaline conditions and high sensitivity to oxidation in the presence of slight oxidizing agents such as hydrogen peroxide, which is present in honey and is responsible for the degradation veriied in the lavonoids analyzed [24,25].…”

Contribution of honey in nutrition and human health: a review

“…The distribution of three main phenolic families (benzoic acids, cinnamic acids and flavonoids) shows different profiles in honey from different floral origins, with flavonoids being the most common in floral honeys. Therefore, a characteristic distribution pattern of phenolic compounds should be found in unifloral honeys sourced from the corresponding plant sources [39][40][41][42][43]. The flavonoids in honey and propolis have been identified as flavanones and flavanones/flavanols.…”

“…In general, the flavonoid concentration in honey is approximately 20 mg/kg [44,45]. Polyphenols in honey are mainly flavonoids (e.g., quercetin, luteolin, kaempferol, apigenin, chrysin, galangin), phenolic acids and phenolic acid derivatives [38,39,41,42,[44][45][46]. The major flavonoids identified in various honeys are represented in Table 3.…”

Characterisation of insect and plant origins using DNA extracted from small volumes of bee honey

“…However, the sequences obtained from sample HA, are a 100% match on the species Robinia pseudoacacia, a species within the subfamily Fabaceae-that is often referred to as 'acacia' in Europe. Given that the sample originated from Hungary, it would seem that this would explain the discrepancy (Truchado et al 2008). A second explanation, that might apply to the remaining sample (ST) is that commercial naming guidelines of honeys vary immensely, in particular with regards to what percent of a honey must be derived from a single species in order to receive designation as a monoculture.…”