Identification of 7,4′-dihydroxy-5-methoxyflavylium in "dragon's blood": To be or not to be an anthocyanin

Maria J. Melo, Micaela Sousa, A. Jorge Parola, J. Sérgio Seixas de Melo, Fernando Catarino, Joaquim Marçalo, Fernando Pina

Research output: Contribution to journalArticle

41 Citations (Scopus)

Abstract

The compound 7,4′-dihydroxy-5-methoxyflavylium (dracoflavylium) was identified as the major red colorant in samples of the resin "dragon's blood", extracted from the tree Dracaena draco. The complex network of reversible chemical reactions that dracoflavylium undergoes in aqueous solution is fully described; for the first time, all the equilibrium constants that enable a complete characterisation of the system have been obtained (K′ = 1.6 × 10-4, Kal = 1.0 × 10-4, Ka2 = 3.2 × 10-8, KCt1 = 1.0 × 10 -7, KCt2= 1.3 × 10-10). It is concluded that the red colour is due to a stable quinoid base, A, which is the major species at pH 4-7. It is fur ther shown that this compound does not fit the commonly accepted definitions of anthocyanidin nor 3-deoxyan-thocyanidin. Similarly to synthetic flavylium salts, the natural compound 7,4′-dihydroxy-5-methoxyflavylium gives rise to several species (multistate system) reversibly interconverted by external stimuli, such as pH.

Original languageEnglish
Pages (from-to)1417-1422
Number of pages6
JournalChemistry - A European Journal
Volume13
Issue number5
DOIs
Publication statusPublished - 21 Jun 2007

Keywords

  • Dyes/pigments
  • Flavylium salts
  • Kinetics
  • Multistate systems
  • Natural products

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