Comparative Evaluation of the Concentration of Free Phenolic Compounds and the Antioxidant Activity of Various Buckwheat Samples

• Published in: Journal of analytical chemistry (New York, N.Y.) N.Y.), 2022-08, Vol.77 (8), p.948-956
• Main Authors: Aleksenko, S. S., Kazimirova, K. O., Shtykov, S. N.
• Format: Article
• Language: English
• Subjects: Amino acids; Analytical Chemistry; Antioxidants; Backup software; Buckwheat; Catechin; Chemistry; Chemistry and Materials Science; Comparative analysis; Ethanol; Gluten; Grain; Heat treatment; High performance liquid chromatography; Oxidation; Phenols
• ISSN: 1061-9348; 1608-3199
• DOI: 10.1134/S1061934822080020

In many countries, buckwheat is considered an alternative gluten-free food product with a unique set of proteins and amino acid composition, and also the high antioxidant activity (AOA). This study deals with the assessment and comparison of the AOA and the total concentration of free phenolic compounds in various buckwheat products purchased from supermarkets in four countries. It is shown that the optimal extractant of free phenols from buckwheat grain is a 50% water–ethanol solution; vortexing without heating is sufficient for extraction. Using high-performance liquid chromatography with a diode array detector, fluorescence and MS detectors, the dominant components are quantitatively determined in all buckwheat samples: rutin ((6.7–14.1) × 10 –2 g/kg), flavan-3-ols (catechin (1.8–8.7) × 10 –2 g/kg and epicatechin (2.5–11.6) × 10 –2 g/kg). Protocatechuic and gallic acids, as well as unbound vitexin and quercetin, are detected in minor amounts mainly in heat-treated buckwheat grains. Linear correlations between the total concentration of phenolic compounds, estimated by the Folin–Ciocalteu method, and AOA, as well as between the sum of concentrations of three components (rutin, catechin, and epicatechin) and AOA are obtained. The chromatographic profiles and AOA of buckwheat, wheat, barley, corn, and rice are compared.