Identification and quantification of flavonoid aglycones in rape bee pollen from Qinghai-Tibetan Plateau by HPLC-DAD-APCI/MS

• HPLC-DAD-APCI/MS was set up for analysis of flavonoid aglycones in the RBP.
• The method is capable of providing higher sensitivity and repeatability.
• Four methods were applied and assessed for extraction of flavonoids from RBP.
• The highest extraction efficiency of flavonoids from RBP was achieved by MAE.
• MAE is of short extraction time, low solvent consumption and homogeneous conditions.

For identification and quantification of flavonoid aglycones in rape bee pollen (RBP) collected from the Qinghai-Tibetan Plateau, a high-performance liquid chromatography (HPLC) separation method with diode array detector (DAD) and atmospheric pressure chemical ionization/mass spectrometric (APCI/MS) detection and four extraction methods (i.e. microwave-assisted extraction, Soxhlet extraction, cold-soaked extraction, and heat reflux extraction) were developed in this study. The identification of flavonoid aglycones was based on retention time and mass spectra by comparison with standards. Results demonstrated that this method showed excellent reproducibility and correlation coefficient, and offered the detection limits of 0.77–15.50 pmol at signal-to-noise ratio of 3. Quercetin and kaempferol were presented in RBP, and microwave-assisted extraction (MAE) was superior to the other three methods in terms of efficiency, convenience and high content of quercetin (1.37 ± 0.059 mg/g) and kaempferol (23.44 ± 0.544 mg/g). Our work indicated that: 1) the proposed HPLC-DAD-APCI/MS was an accurate and precise analysis method to identify and quantify the flavonoid aglycones in RBP; and 2) MAE was efficient to extract flavonoids from RBP with short extraction time, low solvent consumption, and homogeneous extraction conditions.