Evaluation of Nutritional Components, Phenolic Composition, and Antioxidant Capacity of Highland Barley with Different Grain Colors on the Qinghai Tibet Plateau

Abstract

The nutritional composition, polyphenol and anthocyanin composition, and antioxidant capacity of 52 colored highland barley were evaluated. The results showed that the protein content of highland barley in the black group was the highest, the total starch and fat contents in the blue group were the highest, the amylose content in the purple group was quite high, the fiber content in the yellow group was quite high, and the β-glucan content of the dark highland barley (purple, blue and black) was quite high. The polyphenol content and its antioxidant capacity in the black group were the highest, while the anthocyanin content and its antioxidant capacity in the purple highland barley were the highest. Ten types of monomeric phenolic substances were the main contributors to DPPH, ABTS, and FRAP antioxidant capacity. All varieties could be divided into four categories according to nutrition or function. The grain color could not be used as an absolute index to evaluate the quality of highland barley, and the important influence of variety on the quality of highland barley also needed to be considered. In actual production, suitable raw materials must be selected according to the processing purpose and variety characteristics of highland barley.

Polyphenol Profile and In Vitro Antioxidant and Enzyme Inhibitory Activities of Different Solvent Extracts of Highland Barley Bran

“…Furthermore, the total phenolic content of the different solvent extracts evaluated was 23.08–78.54-fold higher than the total flavonoid content, indicating a low concentration of flavonoids in highland barley bran polyphenols. This was in agreement with Dang et al’s findings on whole-grain testing of highland barley with different grain colors [ 5 ].…”

“…The main polyphenols found in barley bran include ferulic acid, protocatechuic acid, chlorogenic acid, benzogenic acid, catechin, kaempferol, vanillic acid, p -coumaric acid, and others. We successfully identified all these compounds in our study in different solvent extracts of highland barley bran [ 5 , 28 , 29 ]. López-Perea et al recovered gallic acid, chlorogenic acid, p -coumaric acid, ferulic acid, benzoic acid, quercetin, and kaempferol in an 80% methanol extract, 80% ethanol extract, and 50% acetone extract of barley, similarly to our study [ 30 ].…”

“…On the one hand, total phenols and total flavonoids determined by chemical approaches are measured in gallic acid and rutin equivalents, respectively, whereas total phenols determined by liquid chromatography are quantified in comparison to specific polyphenol standards as controls. On the other hand, highland barley bran is rich in phenolic compounds, and there are other unknown phenolic compounds to be identified [ 5 , 32 ]. In conclusion, the composition and content of polyphenol compounds enriched in the bran of highland barley were different in the solvent systems used.…”

“…Among the polyphenols from highland barley with different grain colors, protocatechuic acid and catechin might be the main contributors to DPPH· free radical scavenging ability. On the other hand, chlorogenic acid and catechin might be the main contributors to FRAP reducing ability, while benzoic acid might be the main contributor to ABTS + · free radical scavenging ability [ 5 ]. Yang et al discovered that in blue-colored highland barley, 2,4-dihydroxybenzoic acid and protocatechuic acid were the main contributors to the free phenol extract scavenging capacity against DPPH· and ABTS + · free radicals, while chlorogenic acid, vanillic acid, ferulic acid, and quercetin contributed to the bound phenol extract free radicals scavenging capacity [ 1 ].…”

“…Colored highland barley, particularly black highland barley, is rich in important functional components such as polyphenols, anthocyanins, and β-glucans. It also appears to have a higher overall edible value than common highland barley, thus receiving increasing attention from the food processing industry [ 5 ]. Regular consumption of whole-grain highland barley improves glucose and lipid metabolism disorders in humans and can contribute to the prevention of obesity and cardiovascular disease [ 6 ].…”