Importance of Insoluble-Bound Phenolics to Antioxidant Properties of Wheat

Abstract

Two commercial samples of soft (70% Canadian Eastern soft red spring and 30% Canadian Eastern soft white winter) and hard (90% Canadian western hard red spring and 10% Canadian Eastern hard red winter) wheats were used to obtain different milling fractions. Phenolics extracted belonged to free, soluble esters and insoluble-bound fractions. Soluble esters of phenolics and insoluble-bound phenolics were extracted into diethyl ether after alkaline hydrolysis of samples. The content of phenolics was determined using Folin-Ciocalteu's reagent and expressed as ferulic acid equivalents (FAE). The antioxidant activity of phenolic fractions was evaluated using Trolox equivalent antioxidant capacity, 2,2-diphenyl-1-picrylhydrazyl radical scavenging, reducing power, oxygen radical absorbance capacity, inhibition of oxidation of human low-density lipoprotein cholesterol and DNA, Rancimat, inhibition of photochemilumenescence, and iron(II) chelation activity. The bound phenolic content in the bran fraction was 11.3 +/- 0.13 and 12.2 +/- 0.15 mg FAE/g defatted material for hard and soft wheats, respectively. The corresponding values for flour were 0.33 +/- 0.01 and 0.46 +/- 0.02 mg FAE/g defatted sample. The bound phenolic content of hard and soft whole wheats was 2.1 (+/-0.004 or +/-0.005) mg FAE/g defatted material. The free phenolic content ranged from 0.14 +/- 0.004 to 0.98 +/- 0.05 mg FAE/g defatted milling fractions of hard and soft wheats examined. The contribution of bound phenolics to the total phenolic content was significantly higher than that of free and esterified fractions. In wheat, phenolic compounds were concentrated mainly in the bran tissues. In the numerous in vitro antioxidant assays carried out, the bound phenolic fraction demonstrated a significantly higher antioxidant capacity than free and esterified phenolics. Thus, inclusion of bound phenolics in studies related to quantification and antioxidant activity evaluation of grains and cereals is essential.

Phenolic Acid Content and Free Radical-Scavenging Activity of Two Differently Processed Carob Tree (<i>Ceratonia siliqua</i> L.) Pod

“…A strong positive correlation (r = 0.999) between DPPH activity and total phenolic content was found for CPF, while a weaker correlation (r = 0.557) was found for CCPF. The present results also agree well with previous findings [17][18][19][20]. The high antioxidant contents of fruits and vegetables have been linked to the inhibition of diseases associated with oxidative damage, such as coronary heart disease, stroke, and cancers.…”

Ferulic acid and derivatives: molecules with potential application in the pharmaceutical field

“…High concentrations of FA may occur in common foods, such as corn bran (2610-3300 mg/100 g), wheat bran (1358-2293 mg/100 g), maize bran (3000 mg/100 g), banana (5.4 mg/100 g), bamboo shoots (243.6 mg/100 g), eggplant (25 mg/100 g), orange (9.2-9.9 mg/100 g), beets (800 mg/100 mg) as well as in broccoli, spinach, cabbage, potatoes, carrots, tomatoes, coffee, natural extracts of herbs and a range of fruits and vegetables (Kroon et al, 1997; Zhao et al, 2005;Mattila et al, 2005; Matilla et al, 2006;Liyana, Shahidi, 2006;Mattila et al, 2007).…”

“…PAL, phenylalanine ammonia-lyase; C4H, cinnamate-4-hydroxylase; 4CL, 4-coumarate:CoA ligase; HCT, hydroxycinnamoyl CoA: quinate/shikimate hydroxycinnamoyl transferase; C3H, coumarate-3-hydroxylase; CCoAOMT, caffeoyl coenzyme A 3-O-methyltransferase; CCR, cinnamoyl CoA reductase; F5H, ferulate 5-hydroxylase; COMT, caffeic acid 3-O-methyltransferase; CAD, cinnamyl alcohol dehydrogenase; ALDH, aldehyde dehydrogenase (Santos et al, 2008). 1997; Zhao et al, 2005;Mattila et al, 2005;Matilla et al, 2006;Liyana, Shahidi, 2006;Mattila et al, 2007).…”

(1.RAR.3),(1.RAR.4)-.BETA.-glucan and Bound Phenolics in Rolled Oats

“…Naczk and Shahidi (1989) recognized the importance of bound phenolics in the total phenolic content. Furthermore, the bound phenolic fraction demonstrated a significantly higher antioxidant capacity than free phenolics in an in vitro antioxidant assay (Liyana-Pathirana and Shahidi, 2006). In rolled oats, the amount of free phenolics may be very low.…”

“…Grains are known to contain phenolic acids such as ferulic and p-coumaric acids (Lempereur et al, 1997;Andreasen et al, 2000), which have functions such as antioxidative activity (Sahidi et al, 1992;Ohta et al, 1994;Castelluccio et al, 1995;Ohta et al, 1997;Andreasen et al, 2001;Liyana-Pathirana and Shahidi, 2006). Therefore, phenolic acids are considered to be important components of rolled oats.…”