Investigating the effect of harvest season on the bioaccessibility of bee pollen polyphenols by ultra-high performance liquid chromatography tandem mass spectrometry

Abstract

Pollen, a natural component of flowers that regulates the reproduction of plants, is in granular form and collected by bees as source of food. A wide range of nutrients including carbohydrates, amino acids, vitamins and polyphenols constitute bee pollen, the latter being responsible for its various biological activities. The aim of the current study was to investigate the effect of harvest season on the bioaccessibility of bee pollen polyphenols. For this purpose, bee pollen samples were collected for 4 consecutive weeks from Domanic, Kutahya, Turkiye. The collected samples were subjected to the standardized INFOGEST in vitro digestion model. The changes in the total phenolics, flavonoids and antioxidant capacity during digestion were measured using spectrophotometric methods, whereas the alterations in individual polyphenols were identified and quantified using ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-ESI-MS/MS). Results of spectrophotometric methods showed that the bioaccessible total phenolics, flavonoids and antioxidants were higher in samples collected at the first week compared to samples collected at the following weeks (18-25%, 38-47% and 52-57%, respectively) (P < 0.05). UPLC-ESI-MS/MS analysis of bee pollen samples led to the identification of 30 major compounds including 17 flavonoids and 13 phenolic acids and other bioactive compounds. In total, the concentration of bioaccessible flavonoids was the highest in samples collected at the first week, whereas samples collected on the third week contained significantly more bioaccessible phenolic acids and other bioactive compounds (P < 0.05). Overall, the current study highlighted that harvest season affects the content and bioaccessibility of bee pollen polyphenols.