TY - JOUR
T1 - Synthesis and equilibrium multistate of new pyrano-3-deoxyanthocyanin-type pigments in aqueous solutions
AU - Sousa, Joana L.C.
AU - Gomes, Vânia
AU - Mateus, Nuno
AU - Pina, Fernando
AU - de Freitas, Victor
AU - Cruz, Luís
N1 - sem pdf conforme despacho.
(PTDC/QEQ-QFI/1971/2014) with financial support from FCT/MEC through national funds and co-financed by FEDER, under the Partnership Agreement PT2020 (UID/QUI/50006/2013 - POCI/01/0145/FEDER/007265). Luis Cruz gratefully acknowledges FCT for his post-doc grant (SFRH/BPD/72652/2010) and an investigator contract (NORTE-01-0145-FEDER-000011).
PY - 2017/10/12
Y1 - 2017/10/12
N2 - Pyrano-flavylium compounds are flavylium derivatives with occurrence in processed foodstuffs such as wine and red fruit juices. In this work, the chemical equilibria of “bio-inspired” pyrano-3-deoxyanthocyanin dyes (4–8), presenting different substituent groups in D ring (10-methyl, 10-catechol, 10-dimethylaminophenyl, 10-carboxy) as well as in B ring (3′,4′-dihydroxy, 4′-carboxy), were studied for the first time in aqueous solutions by UV–Vis spectroscopy. The presence of a methyl group at C-10 (pigment 4) seems to stabilize the flavylium cation (AH+) shifting the deprotonation of 7-OH to a higher pKa1 (pKa1 = 5.0 ± 0.1). On the other hand, the quinoidal bases (A, A−) were more stabilized for the pigments which undergo the first acid-base equilibrium at C-10 substituent, as could be observed by the pKa2 constants (pKa2 = 8.4 ± 0.1 and pKa2 = 8.1 ± 0.1, pigments 6 and 8, respectively).
AB - Pyrano-flavylium compounds are flavylium derivatives with occurrence in processed foodstuffs such as wine and red fruit juices. In this work, the chemical equilibria of “bio-inspired” pyrano-3-deoxyanthocyanin dyes (4–8), presenting different substituent groups in D ring (10-methyl, 10-catechol, 10-dimethylaminophenyl, 10-carboxy) as well as in B ring (3′,4′-dihydroxy, 4′-carboxy), were studied for the first time in aqueous solutions by UV–Vis spectroscopy. The presence of a methyl group at C-10 (pigment 4) seems to stabilize the flavylium cation (AH+) shifting the deprotonation of 7-OH to a higher pKa1 (pKa1 = 5.0 ± 0.1). On the other hand, the quinoidal bases (A, A−) were more stabilized for the pigments which undergo the first acid-base equilibrium at C-10 substituent, as could be observed by the pKa2 constants (pKa2 = 8.4 ± 0.1 and pKa2 = 8.1 ± 0.1, pigments 6 and 8, respectively).
KW - Chemical equilibria
KW - Dyes
KW - pK
KW - Pyrano-3-deoxyanthocyanins
KW - UV–Vis spectroscopy
UR - http://www.scopus.com/inward/record.url?scp=85028769468&partnerID=8YFLogxK
U2 - 10.1016/j.tet.2017.08.051
DO - 10.1016/j.tet.2017.08.051
M3 - Article
AN - SCOPUS:85028769468
SN - 0040-4020
VL - 73
SP - 6021
EP - 6030
JO - Tetrahedron
JF - Tetrahedron
IS - 41
ER -