The pharmacokinetics of anthocyanins and their metabolites in humans

Abstract

Background and purpose: Anthocyanins are phytochemicals with reported vasoactive bioactivity. However, given their instability at neutral pH, they are presumed to undergo significant degradation and subsequent biotransformation. The aim of the present study was to establish the pharmacokinetics of the metabolites of cyanidin-3-glucoside (C3G), a widely consumed dietary phytochemical with potential cardioprotective properties.

Experimental approach: A 500 mg oral bolus dose of 6,8,10,3',5'-(13)C5-C3G was fed to eight healthy male participants, followed by a 48 h collection (0, 0.5, 1, 2, 4, 6, 24, 48 h) of blood, urine and faecal samples. Samples were analysed by HPLC-ESI-MS/MS with elimination kinetics established using non-compartmental pharmacokinetic modelling.

Key results: Seventeen (13)C-labelled compounds were identified in the serum, including (13)C5-C3G, its degradation products, protocatechuic acid (PCA) and phloroglucinaldehyde (PGA), 13 metabolites of PCA and 1 metabolite derived from PGA. The maximal concentrations of the phenolic metabolites (Cmax ) ranged from 10 to 2000 nM, between 2 and 30 h (tmax) post-consumption, with half-lives of elimination observed between 0.5 and 96 h. The major phenolic metabolites identified were hippuric acid and ferulic acid, which peaked in the serum at approximately 16 and 8 h respectively.

Conclusions and implications: Anthocyanins are metabolized to a structurally diverse range of metabolites that exhibit dynamic kinetic profiles. Understanding the elimination kinetics of these metabolites is key to the design of future studies examining their utility in dietary interventions or as therapeutics for disease risk reduction.

Keywords: anthocyanins; ferulic acid; hippuric acid; metabolites; vanillic acid.

Figure 1

Structure of 6,8,10,3′,5′-¹³C₅-cyanidin-3-glucoside.

Figure 2

Serum pharmacokinetic profiles of (A) C3G, (B) PCA and its metabolites and (C) methylated PCA and its metabolites, in humans after the consumption of 500 mg ¹³C₅-C3G in eight healthy male participants. All data are mean ± SEM. C3G, cyanidin-3-glucoside; GlcA, glucuronide; M34dhbz, methyl-3,4-dihydroxybenzoate; PCA, protocatechuic acid; VA, vanillic acid.

Figure 3

Serum pharmacokinetic profiles of (A) benzoic acid metabolites, (B) propenoic acid metabolites, and (C) A-ring-derived and aldehyde metabolites of cyanidin-3-glucoside in humans after the consumption of 500 mg ¹³C₅-C3G in eight healthy male participants. All data are mean ± SEM. BA, benzoic acid; BAL, benzaldehyde; GlcA, glucuronide; PGA, phloroglucinaldehyde.

Figure 4

Urinary elimination profiles of (A) C3G and its metabolites, (B) PCA and its metabolites, and (C) methylated PCA and its metabolites in humans after the consumption of 500 mg ¹³C₅-C3G in eight healthy male participants. All data are mean ± SEM. C3G, cyanidin-3-glucoside; Cy, cyanidin; GlcA, glucuronide; M34dhbz, methyl-3,4-dihydroxybenzoate; Me, methylated; P3G, peonidin-3-glucoside; PCA, protocatechuic acid; VA, vanillic acid.

Figure 5

Urinary elimination profiles of (A) benzoic acid metabolites, (B) propenoic acid metabolites, and (C) A-ring-derived and aldehyde metabolites of cyanidin-3-glucoside in humans after the consumption of 500 mg ¹³C₅-C3G in eight healthy male participants. All data are mean ± SEM. 4-HBAL, 4-hydroxybenzaldehyde; BA, benzoic acid; BAL, benzaldehyde; GlcA, glucuronide; PAA, phenylacetic acid; PGA, phloroglucinaldehyde.

Figure 6

Proposed pathway for the metabolism of cyanidin-3-glucoside in humans. *Conjugates represent unknown structural position. BA, benzoic acid; BAL, benzaldehyde; C3G, cyanidin-3-glucoside; Cy, cyanidin; GlcA, glucuronide; Me, methoxy; M34dhbz, methyl-3,4-dihydroxybenzoate; P3G, peonidin-3-glucoside; PAA, phenylacetic acid; PGA, phloroglucinaldehyde.