undergraduate thesis
Uključenost α-, γ-, δ- tokoferola u bifazni mehanizam kinetike nestanka DPPH radikala

Anja Iskra (2016)
Sveučilište u Rijeci
Medicinski fakultet
Katedra za kemiju i biokemiju
Metadata
TitleUključenost α-, γ-, δ- tokoferola u bifazni mehanizam kinetike nestanka DPPH radikala
AuthorAnja Iskra
Mentor(s)Dalibor Broznić (thesis advisor)
Abstract
Antioksidansi smanjuju ili uklanjaju negativne učinke slobodnih radikala. Vitamin topljiv u mastima s najboljim antioksidacijskim svojstvima je vitamin E. U prirodi postoji osam različitih vrsta tog vitamina, a to su α-, β-, γ-, δ-tokoferoli i tokotrienoli. Mnogi antioksidansi, pa tako i različite vrste vitamina E, reagiraju različitim brzinama s radikalima te je njihovo antioksidacijsko djelovanje različito. U ovom istraţivanju analizirana je i odreĎena antioksidacijska aktivnost pojedinačnih izomera vitamina E (α-, γ- i δ-tokoferola) te njihovih meĎusobnih kombinacija. Antioksidacijska aktivnost uzoraka prikazana je gubitkom signala DPPH radikala i u odnosu na koncentraciju izračunatom metodom Trolox. Gubitci signala α-, γ- i δ-tokoferola su puno manji u odnosu na kombinacije tih istih izomera čime se moţe zaključiti da je antioksidacijska aktivnost, odnosno kapacitet hvatanja DPPH radikala, puno veći u kombinacijama dvaju ili više izomera nego kod pojedinačnih izomera. Antioksidacijska aktivnost dobivena metodom DPPH razlikuje se s obzirom na antioksidacijsku aktivnost dobivenu metodom Trolox kada se uvaţava i masa izomera u uzorku. OdreĎivanjem antioksidacijske aktivnosti pomoću metode Trolox uzima se u obzirom masa izomera vitamina E u uzorku te je dokazano da najveću antioksidacijsku aktivnost ima α-tokoferol, a najmanju δ-tokoferol. Usporedbom kinetičkih podataka i statističkih pokazatelja za monofazne i bifazne modele dokazuje se najbolja prihvatljivost bifaznog modela kinetike prvog reda za opis kinetike nestanka DPPH radikala u uzorcima izomera vitamina E i njihovih meĎusobnih kombinacija. Dobiveni rezultati pokazali su da se reakcija odvija u dva stupnja, brţa reakcija u početnih 5 do 10 minuta, nakon čega slijedi sporija reakcija.
Keywordsα-tocopherol γ-tocopherol δ-tocopherol DPPH • kinetics biphasic first-order kinetic model
Committee MembersMarin Tota (committee chairperson)
Ivana Gobin (committee member)
Dalibor Broznić (committee member)
GranterSveučilište u Rijeci
Medicinski fakultet
Lower level organizational unitsKatedra za kemiju i biokemiju
PlaceRijeka
StateCroatia
Scientific field, discipline, subdisciplineBIOMEDICINE AND HEALTHCARE
Basic Medical Sciences
Medical Biochemistry
Study programme typeuniversity
Study levelundergraduate
Study programmeStudy of Sanitary Engineering
Academic title abbreviationuniv. bacc. sanit. ing.
Genreundergraduate thesis
Language Croatian
Defense date2016-09-13
Parallel abstract (English)
Antioxidants reduce or eliminate the negative effects of free radicals. Vitamin E is fat soluble vitamin with the best antioxidant properties. In nature, there are eight different types of this vitamin, such as α-, β-, γ-, δ-tocopherols and tocotrienols. Many antioxidants, including different types of vitamin E react with radicals at various speeds, hence their different antioxidant activity. This research analyses and determines the antioxidant activity of the individual isomers of vitamin E (α-, γ- and δ-tocopherol) and their combinations. The activity of the antioxidant sample was shown by losing the signal of DPPH radical and in the relation to the concentration calculated from Trolox method. Losses of the signal of α-, γ- and δ-tocopherols are much smaller compared to the combinations of the same isomers, based on which it can an be concluded that the antioxidant activity or the capacity to capture DPPH radicals is much higher in combinations of two or more isomers than in individual isomers. The antioxidant activity obtained by the DPPH method is different with regard to antioxidant activity obtained by the Trolox method which recognizes the masses of isomers in the sample. In determining the antioxidant activity using the Trolox method, the mass of vitamin E isomers in the sample taken into account, and it is proven that α-tocopherol has the highest antioxidant activity, while it is the lowest in the case of δ-tocopherol. In the comparison of the kinetic data and the statistical indicators for monophasic and biphasic models proves the best acceptability of the biphasic first-order kinetic model to describe the kinetics of DPPH radical disappearance in samples of vitamin E isomers and their mutual combination. The results showed that the reaction takes place in the two phases; first rapid phase during the initial 5 – 10 minutes of the reaction when follow the second much slower phase.
Parallel keywords (Croatian)α-tokoferol γ-tokoferol δ-tokoferol DPPH· kinetika bifazni model kinetike prvog reda
Resource typetext
Access conditionAccess restricted to students and staff of home institution
Terms of usehttp://rightsstatements.org/vocab/InC/1.0/
URN:NBNhttps://urn.nsk.hr/urn:nbn:hr:184:073804
CommitterBosa Licul