Evaluation of polyphenolic and flavonoid compounds in honeybee-collected pollen produced in Spain.

Polyphenolic content, flavonoid content, and free flavonoid aglycon compounds were determined in 11 samples of Spanish honeybee-collected pollen. Adequate extraction was obtained with ethyl acetate in the determination of free flavonoid aglycon. Recovery (>83.6%), within-run repeatability (<6.67%), between-run reproducibility (<8.73%), and detection limits (1.4--1.9 mg/kg) were satisfactory. A total of 15 compounds were separated with gradient reversed phase HPLC, and 13 were identified and quantified using diode array detector. The most predominant compounds were flavonoid glycosides, mainly flavonols. Eighty-two percent of the samples contained at least 14 of the phenolic components, primarily rutin, quercetin, myricetin, and trans-cinnamic acid as free aglycons. Total phenols were present, at levels of >0.85 g/100 g in the form of non-tannins, and flavonoids of >0.35 g/100 g, using spectrophotometric procedures. Rutin is the best identifier of free flavonoid aglycon compounds. A minimum quantity of 200 mg/kg of rutin is suggested to guarantee the nutritional and biological properties required in the European market.