Extraction, Distribution And Antioxidant Activities Of Phenolic Acids In Pigmented Wheat Bran

Pigmented wheat has different color in the kenel pericarp or aleuronic layer and isdifferent from the common white wheat. Pigmented Wheat consist of blue，purple, black,green and red pericarp ones of them. They are precious new varieties of wheat. Manycultivars pigmented wheat have been showed to contain rich natural pigment, protein, amidacid and microelements or antioxidant substance which are benefit to human health. Andthere are lots of natural phenolic acids in the wheat bran which have high application valueand development prospects.This study used the bran of the Shandong Agricultural University self-cultivate blue,purple, black wheat for materials. The extraction methods, the distribution and antioxidantactivities of phenolic acids in the bran were studied. The main results in the paper were asfollows：(1) The effect of extraction solvents on wheat bran antioxidant activity estimation.The80%methanol extract exhibited the greater total phenol content and total antioxidantactivity than80%ethanol and acidic ethanol. The acidic ethanol extract exhibited the greatertotal anthocyanin content and DPPH scavenge activity than80%methanol and80%ethanol.In a word,80%methanol was a recommended solvent for extracting phenolic antioxidantsfrom wheat bran.(2) Study on extraction methods of phenolic acids in wheat bran.Hydrolysis conditions had significant influence on the release of phenolic acids.Alkaline-acid hydrolysis was more effcient in releasing the phenolic acids than acid-alkalinehydrolysis. The optimal conditions were found as follows: alkaline hydrolysis (2mol/L NaOH,4h, at room temperature) followed by acid hydrolysis (2mol/L HCL,1h at85°C).Under theabove-mentioned condition, the total content of bound phenolic acids was4719μg/g bran.(3) Distribution of phenolic acids and antioxidant activities of different bran fractionsfrom pigmented wheat.The distribution of phenolic acids in the three pigmented wheat bran was different.Phenolic acid content and antioxidant activity decreased in the order of outer bran, coarsebran and shorts. The species differences of phenolic acids were very small. Bound phenolicacids were the predominant phenolic acids in the wheat bran. Of bound phenolic acids, the highest content of ferulic acid was observed in all the samples. Among the three pigmentedwheat, the bran fractions from blue wheat contained higher bound phenolic acids than theother two pigmented wheat bran fractions. High correlation were observed between TPC andradical scavenging capacities for DPPH and ABTS (R2>0.85, p<0.05).(4) The effect of solid state alkaline hydrolysis on purple wheat bran antioxidant activityestimation.The solid state alkaline hydrolysis can increase the total phenolic content and antioxidantactivity of40-mesh bran, while the process reduced those of ultramicroporwderized bran.With the increased of concentration of alkali, the total phenolic content and antioxidantactivity showed a rise trend. The mild thermal treatment (60°C) may enhance the antioxidantactivity of wheat bran. The increased of the heating duration did not show significant effect onwheat bran.