Identification of 7,4′‐Dihydroxy‐5‐methoxyflavylium in “Dragon's Blood”: To Be or Not To Be an Anthocyanin

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'(a)=1.6 x 10(-4), K(a1)=1.0 x 10(-4), K(a2)=3.2 x 10(-8), K(Ct1)=1.0 x 10(-7), K(Ct2)=1.3 x 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 further shown that this compound does not fit the commonly accepted definitions of anthocyanidin nor 3-deoxyanthocyanidin. 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.

Phytochemical profiles and inhibitory effect on free radical-induced human erythrocyte damage of Dracaena draco leaf: A potential novel antioxidant agent

“…Some phenolic compounds have been identified in D. draco resin (Camarda, Merlini, & Nasini, 1983;González, Léon, Sánchez-Pinto, Padrón, & Bermejo, 2000;González et al, 2004;Melo et al, 2007), including the 2,4,4 0 -trihydroxydihydrochalcone, 3-(4-hydroxybenzyl)-5,7-dimethoxychroman and 7-hydroxy-3-(4-hydroxybenzyl)-chromone, which were described for the first time in nature by González et al (2000). Recently, dracoflavylium was isolated and identified as the major red colourant in this resin (Melo et al, 2007). In addition, Hernández et al (2006) reported the isolation from the D. draco leaves and the structural determination of the new homo-isoflavonoid dracol.…”

Photochromism in Ionic Liquids. Theory and Applications

“…[5] This family of compounds comprises anthocyanins, the ubiquitous colorants of flowers and fruits. In spite of the fact that anthocyanins by themselves do not show significant photochromism, many synthetic [5] and also natural [6] flavylium derivatives exhibit a versatile photochemistry. The photochromic behaviour of synthetic flavylium compounds, more properly the one of the trans-chalcone species, only recently was perceived as a new photochromic system with many potentialities.…”

“…The ionic liquid can influence the photo-induced step that gives the photoproduct or the thermal back reaction. 6 ] and aqueous glycerol (90% wt glycerol:3% wt water). [34] In the case of DODCI, it was observed that the non-radiative rate constant, which represent the rates of photoisomerization, are almost identical in the ionic liquid and aqueous glycerol at a given temperature, confirming that the viscosity governs the photoisomerization of this compound.…”

“…This is due to the zwiterionic character of merocyanine, stabilized in polar solvents, differently from the closed form, stabilized in non-polar solvents. The photo and solvatochromic properties of nitrobenzopyran was studied in ILs: i) containing the same bistrifluoromethanesulfonylimide [NTf 2 ] -anion and several cations, entries 10 to 15 in Table 1, set A in Scheme 4.2, [35] ii) possessing the same phosphonium [P 6,6,6,14 Table 1, set C in Scheme 4.2. Similarly to the behaviour in molecular solvents, irradiation of BSP-NO 2 in these ILs leads to the merocyanine (MC).…”

Novel Flavonoids in Dragon's Blood of Daemonorops draco

“…-Dragons blood is a common name of a red resin obtained from different genera such as Daemonorops (Arecaceae), Dracaena (Agavaceae), Pterocarpus (Leguminosae), and Croton (Euphorbiaceae). Each generous plant produces red pigments of dracorhodin [1], dracoflavylium [2], santalin A [3], and procyanidin B1 [4], respectively, which unequivocally identify the original source of the resin.…”