Digestive behavior and bioavailability of flavan -3 -ols

Andrew P Neilson, Purdue University

Abstract

Increased interest in potential health-protective activities of flavonoid-rich foods has created the need to take advantage of HPLC column and system advances in order to optimize methodologies for flavonoid analysis. Two new RP-C18 methods for HPLC-DAD analysis of tea flavonoids were developed to facilitate separation of catechins within 5 min and separation of catechins and theaflavins within 10 min total analysis time. Catechins were subjected to in vitro gastric and small intestinal digestion. EGCG, EGC, and ECG were significantly degraded at all concentrations tested, with losses of 71–91, 72–100, and 60–61%, respectively. EC and C were comparatively stable, with losses of 8–11 and 7–8%, respectively. HLPCESI-MS/MS indicated that EGCG degradation under simulated digestion resulted in production of theasinensins (THSNs) A and D (m/z 913) and P-2 (m/z 883), its autoxidation homodimers. EGC dimerization produced the homodimers THSN C and E (m/z 609) and homodimers analogous to P-2 (m/z 579). ECG homodimers were not observed. EGCG and EGC formed heterodimers analogous to the THSNs (m/z 761) and P-2 (m/z 731). EGCG and ECG formed homodimers analogous to the THSNs (m/z 897). This study provides an expanded profile of catechin dimers of digestive origin that may potentially form following consumption of catechins. These data provide a logical basis for initial screening to detect catechin digestive products in vivo. There is debate regarding whether the formation of such dimers occurs post-absorption in vivo, due to the low partial pressure of dissolved O2, which catalyzes the dimerization reaction in solution. Using highly differentiated Caco-2 human intestinal cell monolayers as a model of intestinal absorption, both monomers and selected isomers of these dimers were detected in the respective cell extracts following exoposure for up to 3 h. Phase-II metabolites (O-methyl and sulfated forms) of selected dimers were also observed in cells. The dimers appeared to have a significantly greater net accumulation (on a % basis) than the monomers, albeit with greater variability. Additionally, THSNs appear to be degraded to form P-2 upon absorption by intestinal cells. Thus, the intestinal epithelia may accumulate relatively higher levels of these dimers if present in the foods and beverages, or if formed through digestion of monomeric catechins. Conflicting data exist regarding the influence of chocolate matrices on the bioavailability of epicatechin (EC) from cocoa. The objective of this study was to assess the bioavailability of EC from matrices varying in macronutrient composition and physical form. EC bioavailability was assessed from chocolate confections [reference dark chocolate (CDK), high sucrose (CHS), high milk protein (CMP)] and cocoa beverages [sucrose milk protein (BSMP), non-nutritive sweetener milk protein (BNMP)], in humans and in vitro. Six subjects consumed each product in a randomized crossover design with serum EC concentrations monitored over 6 h post-consumption. Areas under the serum concentration-time curve (AUC) were similar among chocolate matrices. However, AUCs were significantly increased for BSMP and BNMP (132 and 143 nM h) vs. CMP (101 nM h). Peak serum concentrations (CMAX) were also increased for BSMP and BNMP (43 and 42 nM) compared to CDK and CMP (32 and 25 nM). In vitro bioaccessibility and Caco-2 accumulation did not differ between treatments. These data suggest that bioavailability of cocoa flavan-3-ols is likely similar from typical commercial cocoa based foods and beverages, but that the physical form and sucrose content may influence TMAX and CMAX. The impact of carbohydrates and milk on the bioavailability of catechin (C) and epicatechin (EC) from chocolate has been extensively studied. However, little data exists regarding the potential modulation of phase-II metabolism by these common chocolate matrix factors. The objectives of this study were to assess the impact of matrix composition on the qualitative and quantitative profiles of circulating native compounds and their metabolites following administration of commercially relevant chocolate confections. Milk and sucrose appear to significantly modulate the metabolism and plasma pharmacokinetics, and to a lesser extent the overall bioavailability, of catechins from chocolate confections. (Abstract shortened by UMI.)

Degree

Ph.D.

Advisors

Ferruzzi, Purdue University.

Subject Area

Toxicology|Nutrition|Agriculture

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