Background and PurposeAnthocyanins 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 ApproachA 500 mg oral bolus dose of 6,8,10,3′,5′-13C5-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 ResultsSeventeen 13C-labelled compounds were identified in the serum, including 13C5-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 ImplicationsAnthocyanins 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.

Scope: Numerous studies feeding anthocyanin-rich foods report limited bioavailability of the parent anthocyanins. The present study explores the identity and concentration of the phenolic metabolites of anthocyanins in humans. Methods and results: Anthocyanin metabolites were quantified in samples collected from a previously conducted 12-wk elderberry intervention study in healthy post-menopausal women. Individual 1-, 2-and 3-h post-bolus urine samples and pooled plasma samples following acute (single bolus) and chronic (12-wk supplementation) anthocyanin consumption (500 mg/day) were analysed using HPLC-ESI-MS/MS. Twenty-eight anthocyanin metabolites were identified in urine and 21 in plasma (including sulfates of vanillic, protocatechuic and benzoic acid). Phenolic metabolites reached peak concentrations of 1237 nM in plasma, while anthocyanin conjugates only reached concentrations of 34 nM. Similarly, in urine, phenolic metabolites were detected at concentrations of 33 185 ± 2549 nM/mM creatinine, while anthocyanin conjugates reached concentrations of 548 ± 219 nM/mM creatinine. There was no evidence that chronic exposure had any impact on either the profile or quantity of metabolites recovered relative to acute exposure. Conclusion: An extensive range of phenolic metabolites of anthocyanin was identified following elderberry consumption in humans, including 11 novel metabolites, which were identified at much higher concentrations than their parent compounds.

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High intakes of anthocyanins (ACN) have been linked to decreased cardiovascular disease risk. However, due to their apparent low bioavailability, it has been postulated that phenolic degradation products of ACNs may be responsible for their bioactivity. We examined the metabolic fate of ACNs following a single dose and short‐term (12 wk) exposure to an elderberry extract, to establish the differential effects of acute v short‐term exposure on metabolism. Biological samples from a 12 wk intervention study (n=15 postmenopausal women, 500 mg/day elderberry ACNs) were analysed for ACN metabolites using HPLC‐MS/MS. 29 metabolites were identified in urine (12 ACN and 17 phenolic metabolites) and 21 in plasma (4 ACN and 17 phenolic metabolites). ACNs reached concentrations of 0.55±0.05 μM/mM creatinine in urine after 3h and 0.034 μM in plasma after 2h. The phenolic degradation products and their metabolites reached concentrations of 31.15±2.37 μM/mM creatinine in urine after 3h and 1.24 μM in plasma after 2h. The profile of metabolites was not significantly different after 12 wks of intake. These results indicate that ACNs are extensively metabolised in vivo, with little suggestion of plasma accumulation following repeated exposure. The reported bioactivity of ACN most likely relates to the high concentrations of circulating phenolic metabolites. Research support: Norwich Medical School, University of East Anglia.Grant Funding Source: Department of Nutrition, Norwich Medical School, University of East Anglia.