Investigating the Interaction of Ascorbic Acid with Anthocyanins and Pyranoanthocyanins

Abstract

Juices colored by anthocyanins experience color loss related to fortification with ascorbic acid (AA), thought to be the result of condensation at Carbon-4 of anthocyanins. To further understand this mechanism, pyranoanthocyanins, having a fourth-ring covalently occupying Carbon-4, were synthesized to compare its reactivity with AA against that of anthocyanins. Pyranoanthocyanins were synthesized by combining chokeberry anthocyanins with pyruvic acid. AA (250–1000 mg/L) was added to either chokeberry extract, cyanidin-3-galactoside, or 5-Carboxypyranocyanidin-3-galactoside. Samples were stored in the dark for 5 days at 25 °C and spectra (380–700 nm), color (CIE-L*c*h*), and composition changes (HPLC-MS/MS) were monitored. Extensive bleaching occurred for cyanidin-3-galactoside and chokeberry colored solutions, with a decrease in half-lives from 22.8 to 0.3 days for Cyanidin-3-galactoside when 1000 mg/L AA was added. 5-Carboxypyranocyanidin-3-galactoside solution better maintained color with limited loss in absorbance, due to the formation of colored degradation products (λvis-max = 477 to 487 nm), and half-life decrease from 40.8 to 2.7 days, an 8–13-fold improvement compared to anthocyanins. This suggested alternative sites of reactivity with AA. Carbon-4 may be the preferred site for AA-pigment interactions, but it was not the only location. With Carbon-4 blocked, 5-Carboxypyranocyanidin-3-galactoside reacted with AA to form new pigments and reduce bleaching.

Cyanidin 3-O-galactoside: A Natural Compound with Multiple Health Benefits

“…Many other external treatments upon food containing Cy3Gal had been proved to be capable of affecting the stability of this compound, such as adding exogenous additives, such as vitamin C and phenolic acids, high hydrostatic pressure treatment, vacuum-microwave and freeze drying, heat and microwave pretreatment, etc. [ 51 , 53 , 63 , 64 , 65 ]. Some of these methods have already been industrially employed.…”

The Effect of Plant Additives on the Stability of Polyphenols in Cloudy and Clarified Juices from Black Chokeberry (Aronia melanocarpa)

“…The concentration of anthocyanins in sweet potato decreased as the concentration of ascorbic acid increased, and it was clearly noticeable at 25 • C [56]. Farr and Giusti [57] noted high values of t 1/2 = 858 h for the anthocyanin chokeberry extract. When ascorbic acid was added at amounts of 250, 500, and 1000 mg/L, it accelerated the degradation of anthocyanins in the extract, which resulted in lower half-life values, i.e., t 1/2 = 68, 43 and 24 h, respectively.…”

“…The pH of the juices/drinks tested in the study (pH = 3.42-3.52) favoured the stability of anthocyanins and polyphenols (unpublished data). According to Farr and Giusti [57], the reactivity of ascorbic acid with C-4 carbon in anthocyanins is the mechanism catalysing their degradation. When cyanidin-3-O-galactoside was synthesised with pyruvic acid, the resulting product was pyranoanthocyanin with blocked C-4 carbon.…”

Camu-camu (Myrciaria dubia) and jambolan (Syzygium cumini) juice blend: sensory analysis and bioactive compounds stability

“…The presence of AA has shown a negative impact on the stability of anthocyanin, and the degradation mechanism consists of the direct condensation of AA with the anthocyanin molecule leading to the mutual loss of these compounds (Nikkhah et al, 2010). On the other hand, the loss of anthocyanin color in the presence of AA can occur due to oxidative cleavage of the pyrylium ring by a free radical mechanism, in which AA acts as a molecular oxygen activator and produces free radicals (Farr & Giusti, 2018). In addition, the presence of flavonol exerts a protective effect against the degradation of anthocyanins, in the presence of AA, probably by competing with anthocyanins in the preference for condensation reactions (Cavalcanti et al, 2011).…”