Purple-fleshed sweet potato acylated anthocyanins: Equilibrium network and photophysical properties

Hélder Oliveira, Nuno Basílio, Fernando Pina, Iva Fernandes, Victor de Freitas, Nuno Mateus

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Two anthocyanins from purple-fleshed sweet potato were isolated and characterized by LC–MS and NMR analysis. They were identified as peonidin-3-(6′-hydroxybenzoyl)-sophoroside-5-glucoside and peonidin-3-(6′-hydroxybenzoyl-6″-caffeoyl)-sophoroside-5-glucoside. The acid–base dynamics of these acylated anthocyanins was evaluated by means of pH jump techniques. Equilibrium and kinetic constants were determined and, in general, these anthocyanins demonstrated a higher capacity in retaining the red and blue colors at acidic and basic pH values, suggesting a higher resistance to pH variations compared to the parent anthocyanin, peonidin-3-O-glucoside. The presence of acyl groups and additional glucoside moieties seems to determine this particular characteristic. The fluorescence properties of these anthocyanins were evaluated. Overall, the species present at higher pH values (7–9) showed higher fluorescence intensity for both anthocyanins, with an optimum λ exem pair at λ ex 610 nm/λ em 640 nm. The fluorescence characteristics of these anthocyanins were used to evaluate their location in gastric and intestinal cells by fluorescence microscopy.

Original languageEnglish
Pages (from-to)386-394
Number of pages9
JournalFood Chemistry
Volume288
DOIs
Publication statusPublished - 1 Aug 2019

Keywords

  • Acylated anthocyanins
  • Chemical equilibria
  • Fluorescence
  • Purple-fleshed sweet potato

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