Total phenolics and antioxidant activity of feed components

V diplomski nalogi smo določali vsebnost skupnih fenolov in ocenili antioksidativni potencial v sedmih sestavinah krme: v pšenici, ječmenu, koruznem šrotu, otrobih, repičnih tropinah, sojinih tropinah, koruznem glutenu ter v krmnih mešanicah Bek-1 in Bek-2. Vzorce smo liofilizirali in ekstrahirali z različnimi topili in ekstrakcijskimi postopki. Na podlagi rezultatov smo kot najučinkovitejše topilo izbrali vodno raztopino acetona (aceton: voda, 70:30, v/v) in ekstrakcijo z ultrazvočnimi valovi. Skupne fenole smo določili spektrofotometrično s Folin-Ciocalteu metodo. Antioksidativni potencial smo ocenili z ABTS-metodo. Meritve so temeljile na redukciji ABTS∙+_radikala, ki se tvori pri oksidaciji med ABTS-om (2,2`azino-bis (3-etilbenztiazolin 6-sulforonska kislina)) in kalijevim peroksodisulfatom. Skupne fenole in antioksidativni potencial smo merili v acetonskem ekstraktu in v ekstrakcijskem preostanku, v katerem smo izvedli dva različna kislinska postopka, da so se sprostili hidrolizabilni in neekstrabilni kondenzirani tanini. Najvišjo vsebnost skupnih fenolov smo določili v koruznem glutenu (5461 mg GAE (ekvivalent galne kisline) /100g suhe snovi (SS)) in najnižjo v pšenici (1219 mg GAE/100g SS). Najvišji antioksidativni potencial smo ponovno ocenili pri koruznem glutenu (1656 µmol Trolox ekvivalenta (TE) /g SS in najnižjega pri koruznem šrotu (254 µmol TE/g SS). K skupnim fenolom so največ prispevali hidrolizabilni taninski fenoli (37–54 %), sledili so neekstrabilni kondenzirani taninski fenoli (20–50 %) in ekstrabilni fenoli (4,8–40 %). Izjema so bile repične tropine, kjer so prevladovali ekstrabilni fenoli. Ekstrabilni antioksidanti so k celokupnemu antioksidativnemu potencialu prispevali največ do 17 %, medtem ko je bil antioksidativni potencial povezan z neekstrabilnimi kondenziranimi in hidrolizabilnimi taninskimi fenoli znatno višji.The aim of graduation thesis was to determine total phenolics and also to estimate antioxidant activity in seven feed components: wheat, barley, corn grit, wheat bran, rapeseed, soybean, corn gluten, and in two feed mixtures Bek-1 and Bek-2. Samples were lyophilized and extracted using different solvents and extraction procedures. The results showed that the most efficient extraction procedure was a sonication using aqueous acetone solution (acetone:water, 70:30, v/v). Total phenolics were determined spectrophotometrically according to Folin-Ciocalteu method. Antioxidant potential of extracts was estimated by ABTS method. Measurements were based on the reduction of radical cation (ABTS∙+) which was formed through the reaction of oxidation between ABTS (2,2 –azino-bis-(3-ethylbenzothiazolin-6- sulfonic acid)) and potassium peroxodisulphate. The remaining amount of ABTS∙+ was determined spectrophotometrically at wavelength of 734 nm. Total phenolic contents and antioxidant activity were measured in aqueous-organic extracts, as well as in extraction residues which were subject of two different acidic treatments to release hydrolysable tannins and non-extractable condensed tannins. The highest content of total phenolics was found in corn gluten (5461 mg of gallic acid equivalent (GAE)/100g of dry weight (DW)) and the lowest in wheat (1219 mg GAE/100g DW). The highest antioxidant activity was again estimated in corn gluten (1656 µmol of Trolox equivalent (TE)/g DW) and the lowest in corn grit (254 µmol TE/g sample). Hydrolysable tannins were the major contributors to the total phenolics (37 - 54 %), followed by condensed tannins (20 - 50 %) and extractable phenolics (4,8 - 40 %). The only exception was the rapeseeds in which extractable phenolics dominated. Extractable antioxidants contributed less than 17 % to total antioxidant activity, considerably higher values of antioxidant activity were associated with non-extractable condensed tannins and hydrolysable tannins