Exploring the bioaccessibility and intestinal absorption of major classes of pure phenolic compounds using in vitro simulated gastrointestinal digestion

Abstract

The bioaccessibility and bioavailability of phenolic compounds (PC) influence directly their role in disease prevention/control. Studies have evaluated this ability through complex plant and food matrices, which may reflect more a synergistic effect of the matrix than the ability of the PCs, hindering their individual exploitation in nutraceutical or pharmaceutical applications. In the present study ten pure PCs representing major classes were evaluated for their bioaccessibility and intestinal absorption in an in vitro simulated gastrointestinal digestion (SGD). This is the first study concerning the bioaccessibility evaluation of pure phloretin, phloroglucinol, naringin, naringenin and daidzein, while no in vitro SGD has been performed before for the other compounds considered here. PCs were analyzed through ultra-high-performance liquid chromatography coupled with diode-array detection and tandem mass spectrometry (UHPLC-DAD-MSⁿ). Most of the compounds remained present along the gastrointestinal tract, and the bioaccessibility was in general higher than 50%, except for quercetin, epigallocatechin gallate, and ellagic acid. All compounds were highly absorbed in the intestine, with phloretin showing the lowest percentage at about 82%. The study findings provide new knowledge on the bioaccessibility and intestinal absorption of different PCs classes.

Keywords: Bioaccessibility; Bioactive compounds; Phenolic compounds; Simulated gastrointestinal digestion.

Fig. 1

- Structures of selected PCs.

Fig. 2

In vitro SGD and sample analysis and quantification by UHPLC-DAD-MSn.

Fig. 3

UHPLC-DAD-MSⁿ chromatograms (acquired at 285 nm) of naringin (NARN) initial ethanol:water (15% v/v) solution and collected samples after the simulated oral, gastric, and intestinal digestion and dialysis (Rt = 14.5 min).

Fig. 4

Concentration (μg mL⁻¹, represented as bars) and bioaccessibilities (B%, represented each replicate as a line) of a) quercetin (QUE), b) rutin (RUT), c) naringenin (NAR), d) naringin (NARN), EGCG, f) apigenin (APG), g) daidzein (DAID), h) phloretin (PH), i) phloroglucinol (PG) and j) ellagic acid (EA) through the in vitroSGD. Different letters indicate significant differences (p < 0.05), determined by one-way ANOVA followed by Bonferroni's post-hoc test. * < LOD and/or LOQ. IS – initial solution, O – oral phase, G – gastric phase, I – intestinal phase.

Fig. 5

IA% of the different PCs after in vitro SGD. Those with an "*" were considered as 100% since the samples collected from inside the dialysis membrane were < LOD and/or LOQ, so not possible to determinate.