Faculty of Food Technology and Biotechnology, University of Zagreb
Abstract
Wheat bran, an important by-product of the cereal industry, is rich in potentially health-promoting phenolic compounds. The phenolics are mainly esterified to the cell wall polysaccharides. In our previous paper, wheat bran was destarched and deproteinated by α-amylase, protease and amyloglucosidase successively and further hydrolyzed using Bacillus subtilis xylanases, and the enzymatic hydrolysates from wheat bran (EHWB) showed good scavenging activity in vitro. The aim of this study is to further characterize the antioxidant potential of EHWB against various systems, both ex vivo and in vivo, namely, rat
liver microsomal lipid peroxidation systems induced by Fe2+/H2O2 and Fe3+-adenosine diphosphate (ADP)/dihydronicotinamide adenine dinucleotide phosphate (NADPH), copper- and 2,2’-azo-bis(2-amidinopropane) dihydrochloride (AAPH)-induced human low-density lipoprotein (LDL) oxidation systems, and alloxan-induced in vivo lipid peroxidation in mice. EHWB inhibited lipid peroxidation in rat liver microsomes induced by Fe2+/H2O2 and Fe3+-ADP/NADPH in a concentration-dependent manner with 90.3 and 87 % inhibition of lipid peroxidation at 50 mg/L, respectively, which were similar to that of butylated hydroxytoluene (BHT) at 20 mg/L. The antioxidant potential of EHWB at a concentration ranging from 10 to 20 mg/L in the nonenzymatic system was more effective than in the enzymatic system. EHWB strongly inhibited in vitro copper- and AAPH-mediated oxidation of LDL in a concentration- and time-dependent manner with 52.41 and 63.03 % inhibition at 20 mg/L, respectively, which were similar to that of ascorbate at 10 mg/L. EHWB significantly decreased the level of thiobarbituric acid reactive substances (TBARS) and increased the activities of glutathione peroxidase (GSH-Px), catalase (CAT) and superoxide dismutase (SOD) in serum and liver of alloxan-treated mice compared with the control. These results demonstrated that EHWB might be efficient in the protection of food products and humans against free radical-induced oxidative damage.Pšenične su mekinje važan nusproizvod u proizvodnji žitarica, jer su bogate fenolnim spojevima što pozitivno utječu na zdravlje. Fenoli se uglavnom vežu esterskom vezom na staničnu stijenku polisaharida. U prijašnjem su istraživanju pomoću α-amilaze, proteaze i amiloglukozidaze iz pšeničnih mekinja uklonjeni škrob i proteini, te su enzimskom hidrolizom pomoću ksilanaza iz bakterije Bacillus subtilis dobiveni hidrolizati, koji su učinkovito uklanjali slobodne radikale in vitro. Svrha je ovoga rada bila iscrpnije opisati antioksidativni učinak tih hidrolizata ex vivo i in vivo u različitim sustavima, i to: sustavima lipidne peroksidacije mikrosoma u jetri štakora induciranih pomoću Fe2+/H2O2 i Fe3+-adenozin difosfata (ADP)/dihidronikotinamid adenin dinukleotid fosfata (NADPH), sustavima oksidacije humanoga lipoproteina male gustoće (LDL) induciranih pomoću bakra i 2,2\u27-azo-bis(2-amidinopropan) dihidroklorida (AAPH), te in vivo lipidnoj peroksidaciji u miševa induciranoj pomoću aloksana. Enzimski su hidrolizati iz pšeničnih mekinja u koncentraciji od 50 mg/L inhibirali lipidnu peroksidaciju u mikrosomima jetre štakora induciranu pomoću Fe2+/H2O2 za 90,3 %, a onu induciranu pomoću Fe3+-ADP/NADPH za 87 %. Taj je učinak sličan učinku butiliranog hidroksitoluena (BHT) u koncentraciji od 20 mg/L. Antioksidativni je učinak enzimskih hidrolizata iz pšeničnih mekinja u koncentracijama od 10 do 20 mg/L bio veći u neenzimskim nego u enzimskim sustavima. Hidrolizati su, ovisno o njihovoj koncentraciji (20 mg/L) i vremenu reakcije, znatno inhibirali in vitro oksidaciju LDL, i to onu induciranu bakrom za 52,41 %, a oksidaciju induciranu pomoću AAPH za 63,03 %, što je slično učinku askorbata pri koncentraciji od 10 mg/L. Također su bitno smanjili količinu reaktivnih spojeva tiobarbiturne kiseline i povećali aktivnost glutation-peroksidaze, katalaze i superoksid dismutaze u serumu i jetri miševa tretiranih aloksanom, u usporedbi s kontrolnim uzorkom. Rezultati pokazuju da enzimski hidrolizati iz pšeničnih mekinja mogu biti korisni u zaštiti prehrambenih proizvoda i zdravlja ljudi od oksidacijskih oštećenja uzrokovanih slobodnim radikalima
