Effects of pH on the stability of cyanidin and cyanidin 3-O-β-glucopyranoside in aqueous solution/Uticaj pH vrednosti sredine na stabilnost cijanidina i cijanidin 3-O-β-glukopiranozida u vodenom rastvoru

• Published in: Hemijska industrija 2015-09, p.511
• Main Authors: Rakic, Violeta P, Skrt, Mihaela A, Miljkovic, Milena N, Kostic, Danijela A, Sokolovic, Dusan T, Ulrih, Natasa E. Poklar
• Format: Article
• Language: English
• Subjects: Anthocyanin; Chemical properties; Chemical reactions; Hydrogen-ion concentration; Identification and classification; Observations
• ISSN: 0367-598X
• DOI: 10.2298/HEMIND140711072R

The colour variation, colour intensity and stability at various pH values (2.0, 4.0, 7.0 and 9.0) of cyanidin 3-O-β-glucopyranoside (Cy3Glc) and its aglycone cyanidin were investigated during a period of 8 hours storage at 25°C. Our data showed that pH of aqueous solution had impact on spectroscopic profile of cyanidin and Cy3Glc. Beginning with the most acidic solutions, increasing the pH induce bathochromic shifts of absorbance maximum in the visible range for all examined pH values (with the exception pH 4.0 for cyanidin), while the presence of the 3-glucosidic substitution induce hypsochromic shift. Compared to cyanidin, Cy3Glc has higher colour intensity and higher stability in the whole pH range, except at pH 7.0. The 3-glucosidic substitution influences on the colour intensity of Cy3Glc in the alkaline region. After 8-hour incubation of Cy3Glc and cyanidin at pH 2.0 and 25°C, 99% of Cy3Glc and only 27% of cyanidin remained unchanged. Keywords: anthocyanins, anthocyanidins, cyanidin, cyanidin 3-glucopyranoside, colour variation, colour intensity, stability, brown index, UV-Vis absorption spectra. U ovom radu ispitivani su varijacija i intenzitet boje i stabilnost cijanidina i cijanidin 3-O-β-glukopiranozida (Cy3Glc) pri razlicitim pH vrednostima (2,0; 4,0; 7,0 i 9,0) tokom inkubacije na temperaturi od 25°C, u periodu od 8 sati. Dobijeni rezultati pokazuju da pH vrednost vodenog rastvora ima uticaj na spektroskopski profil cijanidina i Cy3Glc. Cijanidin i Cy3Glc su pokazali velike razlike u varijaciji i intenzitetu boje, stabilnosti i BI. Pri odredenoj pH vrednosti, te razlike uglavnom rezultiraju iz strukture (prisustva secera na aglikonu). Porast pH vrednosti izaziva batohromno pomeranje apsorpcionih maksimuma u vidljivoj oblasti spektra za sve ispitivane pH vrednosti (osim pH 4,0 za cijanidin), dok je prisustvo 3-glukozidne supstitucije dovodi do hipsohromnog pomeranja. Poredenjem molarnih apsorptivnosti cijanidina i Cy3Glc, uocen je veliki uticaj 3-glukozidne supstitucije: 3-glukozidna supstitucija jako povecava apsorptivnost aglikonskog dela i utice na povecanje intenziteta boje u alkalnom regionu. Tokom inkubacije, prisustvo 3-glukozidne supstitucije jako je uticalo na povecanje molarne apsorptivnosti na svim ispitivanim pH vrednostima kao i na povecanje stabilnosti na pH 2,0 i 4,0. Spektroskopska analiza je pokazala nisku stabilnost aglikona na pH 2,0, bez obzira na cinjenicu da se nalazi u obliku flavilijum katjona. Samo na pH 7,0 stabilnost c