Effective Antioxidant Activities of Anthocyanins as Affected by the pH of Antioxidant Assays

Paradorn Ngamdee, Sudarat Jiamyangyuen


Effect of pH on antioxidant activities of anthocyanins was studied. Five different anthocyanin levels were five black glutinous rice bran crude extracts (BBC), MS, SK, PY, PC, and KK, from Thailand. The antioxidant activities of BBCs were evaluated using two in vitro antioxidant assays conducted at different pH, DPPH (pH 5.5) and FRAP (pH 3.6). Total anthocyanin content (TAC) of KK (23 g/kg) was the highest followed by PC (13 g/kg), PY and SK (11 g/kg), and MS (10 g/kg). The pH of the assays affected the effectiveness of anthocyanins as the KK showed comparable DPPH scavenging activity to other BBCs but exhibited significantly greater FRAP scavenger. To eliminate interferences of other active components in the BBC, anthocyanin-rich isolate (ARI) was isolated from the selected BBC. The ARI contained 90% cyanidin-3-glucoside as analyzed by HPLC. The ARI was dissolved in five different buffer solutions (pH 1, 3, 5, 7, and 9) and incubated for 1 h, 3 days, and 1 week before the evaluation of antioxidant activities. All ARI-containing buffer solutions exhibited comparable DPPH scavenging activity. However, the ones at pH 5 and 7 solutions were less reactive than others as tested with FRAP assay. The results indicated that anthocyanin is a strong antioxidant in an acidic environment. However, derivatives. These results suggest that the application of anthocyanins as natural antioxidants in products, such as food and cosmetic, is not limited by the pH.


Anthocyanins, pH, Antioxidant, DPPH, FRAP


J He and MM Giusti. Anthocyanins: natural colorants with health-promoting properties. Annu. Rev. Food Sci. Technol. 2010; 1, 163-187.

ESM Abdel-Aal, JC Young and I Rabalski. Anthocyanin composition in black, blue, pink, purple, and red cereal grains. J. Agric. Food Chem. 2006; 54, 4696-4704.

P Goufo, J Pereira, J Moutinho-Pereira, CM Correia, N Figueiredo, C Carranca, EAS Rosa and

H Trindade. Rice (Oryza sativa L.) phenolic compounds under elevated carbon dioxide (CO2) concentration. Environ. Exp. Bot. 2014; 99, 28-37.

Y Plaitho, K Kangsadalampai and M Sukprasansap. The protective effect of Thai fermented pigmented rice on urethane induced somatic mutation and recombination in Drosophila melanogaster. J. Med. Plants Res. 2013; 7, 91-98.

D Huang, B Qu and RL Prior. The chemistry behind antioxidant capacity assays. J. Agric. Food Chem. 2005; 53, 1841-1856.

A Castañeda-Ovando, ML Pacheco-Hernández, ME Páez-Hernández, JA Rodríguez and CA Galán-Vidal. Chemical studies of anthocyanins: a review. Food Chem. 2009; 113, 859-871.

BA Cevallos-Casals and L Cisneros-Zevallos. Stability of anthocyanin-based aqueous extracts of Andean purple corn and red-fleshed sweet potato compared to synthetic and natural colorants. Food Chem. 2004; 86, 69-77.

MW Zhang, RF Zhang, FX Zhang and RH Liu. Phenolic profiles and antioxidant activity of black rice bran of different commercially available varieties. J. Agric. Food Chem. 2010; 58, 7580-7587.

R Sompong, S Siebenhandl-Ehn, G Linsberger-Martin and E Berghofer. Physicochemical and antioxidative properties of red and black rice varieties from Thailand, China and Sri Lanka. Food Chem. 2011; 124, 132-140.

MM Giusti and RE Wrolstad. (2001). Characterization and measurement of anthocyanins by UV-visible spectroscopy. In: Wrolstad RE (ed.), Current Protocols in Food Analytical Chemistry. John Wiley & Sons, NY, 2001, p. F1.1.1-F1.2.13.

P Denev, M Ciz, G Ambrozova, A Lojek, I Yanakieva and M Kratchanova. Solid-phase extraction of berries’ anthocyanins and evaluation of their antioxidative properties. Food Chem. 2010; 123, 1055-1061.

L Zhang, Q Fu and Y Zhang. Composition of anthocyanins in pomergranate flowers and their antioxidant activity. Food Chem. 2011; 127, 1444-1449.

OP Sharma and TK Bhat. DPPH antioxidant assay revisited. Food Chem. 2009; 113, 1202-1205.

IFF Benzie and JJ Strain. The ferric reducing ability of plasma (FRAP) as a measure of “Antioxidant Power”: The FRAP assay. Anal. Biochem. 1996; 239, 70-76.

L Ekici, Z Simsek, I Ozturk, O Sagdic and H Yetim. Effects of temperature, time, and pH on the stability of anthocyanin extracts: prediction of total anthocyanin content using nonlinear models. Food Anal. Method. 2014; 7, 1328-1336.

MP Kähkönen and M Heinonen. Antioxidant activity of anthocyanins and their aglycons. J. Agric. Food Chem. 2003; 51, 628-633.

Y Shao, F Xu, X Sun, J Bao and T Beta. Phenolic acids, anthocyanins, and antioxidant capacity in rice (Oryza sativa L.) grains at four stages of development after flowering. Food Chem. 2014; 143, 90-96.

J Kanski, M Aksenova, A Stoyanova and DA Butterfield. Ferulic acid antioxidant protection against hydroxyl and peroxyl radical oxidation in synaptosomal and neuronal cell culture systems in vitro: structure-activity studies. J. Nutr. Biochem. 2002; 13, 273-281.

A Castañeda-Ovando, ML Pacheco-Hernández, ME Páez-Hernández, JA Rodríguez and CA Galán-Vidal. Chemical studies of anthocyanins: a review. Food Chem. 2009; 113, 859-871.

E Sadilova, R Carle and FC Stintzing. Thermal degradation of anthocyanins and its impact on color and in vitro antioxidant capacity. Mol. Nutr. Food Res. 2007; 51, 1461-1471.

R Amorati, GF Pedulli, L Cabrini, L Zambonin and L Landi. Solvent and pH effects on the antioxidant activity of caffeic and other phenolic acids. J. Agric. Food Chem. 2006; 54, 2932-2937.

Z Hou, P Qin, Y Zhang, S Cui and G Ren. Identification of anthocyanins isolated from black rice (Oryza sativa L.) and their degradation kinetics. Food Res. Inter. 2013; 50, 691-697.


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Last updated: 13 February 2019