European Journal of Nutrition

, Volume 44, Issue 3, pp 133–142

In vitro metabolism of anthocyanins by human gut microflora

  • A.-M. Aura
  • P. Martin-Lopez
  • K. A. O’Leary
  • G. Williamson
  • K.-M. Oksman-Caldentey
  • K. Poutanen
  • C. Santos-Buelga
ORIGINAL CONTRIBUTION

DOI: 10.1007/s00394-004-0502-2

Cite this article as:
Aura, AM., Martin-Lopez, P., O’Leary, K.A. et al. Eur J Nutr (2005) 44: 133. doi:10.1007/s00394-004-0502-2

Summary

Background

Only a small part of the dietary anthocyanins are absorbed. Thus large amounts of the ingested compounds are likely to enter the colon. In vitro and in vivo studies have shown that colonic bacteria transform various flavonoids to smaller phenolic acids. However, there is very little information on bacterial transformations of anthocyanins.

Aim of the study

was to explore if anthocyanin glycosides were deglycosylated,whether the resulting aglycones were degraded further to smaller phenolic compounds by colonic bacteria, and to characterise metabolites.

Methods

Isolated cyanidin–3–glucoside and –rutinoside were fermented in vitro using human faecal microbiota as an inoculum. Metabolites were analysed and characterised by HPLC–DAS and LC–MS. They were identified by comparing their characteristics with those of available standards, and semi–quantified using the amount of substrate analysed from samples at initial timepoint.

Results

Cyanidin–3–glucoside and cyanidin aglycone could be identified as intermediary metabolites of cyanidin–3–rutinoside. At early timepoints (before 2 h), the formation of protocatechuic acid as a major metabolite for both cyanidin glycosides and detection of lower molecular weight metabolites show that anthocyanins were converted by gut microflora. Furthermore, reconjugation of the aglycone with other groups, non–typical for dietary anthocyanins, was evident at the later (after 2h) timepoints.

Conclusion

Bacterial metabolism of anthocyanins involves the cleavage of glycosidic linkages and breakdown of the anthocyanidin heterocycle.

Key words

anthocyanins deglycosylation alpha, L-rhamnosidase beta, D-glycosidase bacterial metabolism heterocycle breakdown 

Abbreviations

Cy3g

cyanidin–3–glucoside

Cyrut

cyanidin–3–rutinoside, cyanidin–3–rhamnoglucoside

Cy-1

bacterial metabolite from cyanidin glycosides: aglycone, cyanidin.

Cy-2

bacterial breakdown product from cyanidin glycosides: protocatechuic acid (3,4–dihydroxybenzoic acid)

Cy-3

unidentified bacterial metabolite from cyanidin glycosides

Cy-4

bacterial conjugate of cyanidin possibly containing nitrogen or sulphur

HPLC-DAS

high–performance liquid chromatography–photodiode array spectrometry

Copyright information

© Steinkopff Verlag 2004

Authors and Affiliations

  • A.-M. Aura
    • 1
  • P. Martin-Lopez
    • 2
  • K. A. O’Leary
    • 3
  • G. Williamson
    • 4
  • K.-M. Oksman-Caldentey
    • 1
  • K. Poutanen
    • 1
  • C. Santos-Buelga
    • 2
  1. 1.VTT BiotechnologyEspooFinland
  2. 2.Universidad de SalamancaArea de Nutrición y Bromatología – Facultad de FarmaciaSalamancaSpain
  3. 3.Dept. of Health Toxicology UnitSection on Clinical Pharmacology Imperial CollegeLondonUK
  4. 4.Nutrient Bioavailability GroupNestlé Research Center LausanneSwitzerland

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