Polyphenol characterisation of Phoenix dactylifera L. (date) seeds using HPLC-mass spectrometry and its bioaccessibility using simulated in-vitro digestion/Caco-2 culture model

Abstract

The polyphenolic content in date seeds, a promising functional ingredient for food, was characterised in three forms viz., date seed powder (DSP), date seed pita bread (DSB) and date seed extract (DSE). Bioaccessibility of the polyphenols from the samples was assessed by in-vitro digestion coupled with transport using Caco-2 cells. HPLC-ESI-UV/MS/MS-(IT) analysis recorded the presence of phenolic acids, flavanols, flavonols and flavones. Flavan-3-ols was the most significant group with the highest concentration in DSP, 47.91 ± 0.13 g/kg, after depolymerisation. Phenolic acids such as protocatechuic acid, vanillic acid and caffeoylshikimic acid were recovered from DSP and DSE after in-vitro digestion. In comparison, the recovery was significantly lower in the bread sample. Similarly, transport of protocatechuic acid, p-hydroxybenzoic acid, caffeoylshikimic acid, p-coumaric acid, syringic acid hexoside and diosmin through Caco-2 monolayer was observed in DSP and DSE, while protocatechuic acid and p-hydroxybenzoic acid were the only polyphenols transported from digested DSB.

Keywords: Bioaccessibility; Date seeds; HPLC-mass spectrometry; In-vitro digestion; Phloroglucinolysis; Proanthocyanidins.