Determination of Free and Bound Phenolic Acids, and Evaluation of Antioxidant Activities and Total Polyphenolic Contents in Selected Pearled Barley

Abstract

The content of insoluble bound phenolic acids in pearled barley was determined by an analytical system consisting of alkaline hydrolysis extraction, high-performance liquid chromatographic separation and electrochemical detection. Insoluble bound phenolic acids in five pearled cultivars and fifteen breeding lines of barley comprised ferulic acid (4.3-34.2 mg/100 g dry matter), sinapic acid (0.025-0.445 mg/100 g), caffeic acid (0.002-0.016 mg/100 g). Soluble free polyphenols comprised procyanidins (12.2-80.3 mg/100 g), catechin (0.1-28.2 mg/100 g), and total pholyphenol comprised 152.4-324.0 mg-gallic acid equivalents/100 g. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity for the barley samples ranged from 403 to 1501 μmol-Trolox equivalents/100 g whereas those of oxygen radical absorbance capacity (ORAC) ranged from 1050 to 3816 μmol-Trolox equivalents/100 g. High correlation (0.980, p<0.01) was found between the DPPH and ORAC assays. Total polyphenol contents positively correlated with the DPPH (0.875, p<0.01) and ORAC (0.881, p<0.01) assays. The correlation coefficient between insoluble bound phenolic acids and total polyphenol contents was higher than that between soluble free polyphenols and total polyphenol contents. Taken together, the insoluble bound phenolic acids appear to greately contributed to the antioxidant activity in pearled barley.Keywords: barley, antioxidant, insoluble bound phenolic acid, DPPH, ORAC *To whom correspondence should be addressed. E-mail: hohta@nakamura.ac.jp IntroductionCancer mortality rates due to gastric and uterine cancer are decreasing in Japan, while the cancer mortality rates due to lung, colon and breast cancer are on the rise (Ramarathnam et al., 1997). The steady decline in the incidence of gastric cancer in Japan is attributed to a change in eating habits from the traditional Japanese diet to the Western diet. Epidemiological studies indicate that a high consumption of whole cereal products reduce the risk of cardiovascular diseases and certain cancers (World Cancer Research Fund, 1997; Joint WHO/FAO Expert Consultation, 2003). These effects have been ascribed to dietary fibers and phenolic compounds, including procyanidins and cinnamic acids (Bonoli, 2004). Phenolic compounds have been shown to have strong antioxidant activities in vitro and in vivo associated with their ability to scavenge free radicals to break radical chain reactions and to chelate metals. A wide range of antioxidant components with a phenolic structure such as benzoic and cinnamic derivatives, flavonols, chalcones, and flavones (Hernanz et al., 2001; McMurroufh & Madigan, 1996;Goupy et al., 1999) have been found in both their free and bound forms in cereals. The major free phenolic compounds include procyanidins and flavonoids and the major bound phenolic compounds include hydroxycinnamic acid derivatives such as caffeic, p-coumaric and ferulic acids a DGU-14A degasser, a SCL-10A system controller, an SIL-10AXL auto injector, a CTO-10A column oven, a GL Sciences ED 623 ele...

Phenolic composition as measured by liquid chromatography/mass spectrometry and biological properties of Tunisian barley

“…Several reports have reinforced the case for whole grains as health-promoting components in the diet. [1][2][3] Recently, barley (Hordeum vulgare L.) has gained renewed interest as an ingredient for the production of functional foods and beverages. [4][5][6] Barley is a widely consumed cereal over the world, mainly as animal feed and malt, which is a raw material for the beer and spirit industry.…”

“…[4][5][6] Barley is a widely consumed cereal over the world, mainly as animal feed and malt, which is a raw material for the beer and spirit industry. [3,4,7] Both barley grain and malt contain high levels of antioxidative phenolic compounds. [2][3][4]8] Gupta et al [9] reported that about 80% of phenolic compounds of beer are derived from barley malt and the remaining come from hop, indicating the importance of these compounds during mashing and brewing.…”

“…[3,4,7] Both barley grain and malt contain high levels of antioxidative phenolic compounds. [2][3][4]8] Gupta et al [9] reported that about 80% of phenolic compounds of beer are derived from barley malt and the remaining come from hop, indicating the importance of these compounds during mashing and brewing. Phenolics play an important role in controlling oxidative reactions and extending the shelf life of beer by acting as free radical scavengers, reducing agents, and metal ion chelators.…”

“…[4] Benzoic and cinnamic derivatives, flavonols, chalcones, and flavones were found in both their free and bound forms. [3,14] The major free phenolic compounds include procyanidins and flavonoids, while the major bound ones encompass hydroxycinnamic acid derivatives such as caffeic, p-coumaric, and ferulic acids which link to cell wall by an ester bond. [11] Insoluble bound phenolic acids can be released by acid or alkali hydrolysis.…”

“…[11] Insoluble bound phenolic acids can be released by acid or alkali hydrolysis. [3] However, during brewing, water is used as the extract solvent so that only soluble-free phenolic compounds are present in malt extract. [10,13,15] Therefore, it is meaningful to investigate the fate of free phenolic acids during malting and brewing.…”