undergraduate thesis
Antioksidansi

Marija Knez (2014)
Metadata
TitleAntioksidansi
AuthorMarija Knez
Mentor(s)Elizabeta Has Schon (thesis advisor)
Abstract
Reaktivne kisikove jedinke („reactive oxygen substances“, ROS) i reaktivne dušikove jedinke („reactive nitrogen substances“, RNS) su pojmovi koji opisuju slobodne radikale i ĉestice koje nisu slobodni radikali, a takoĊer imaju oksidativno djelovanje. ROS se odnose na jedinke sa oksidativnim djelovanjem nastale od O₂, dok su radikali jedinke koje sadrže barem jedan nespareni elektron. Veći dio struktura u sastavu ROS-a su slobodni radikali, a ĉine ih superoksidni anion ili superoksid (O₂˙ˉ), hidroksilni radikal (HO˙), peroksilni radikal (RO₂˙), alkoksilni radikal (RO˙) i hidroksilni radikal (OH˙). Reaktivne kisikove jedinke koje nisu slobodni radikali su vodikov peroksid (H₂O₂), hipokloritna kiselina (HOCl), ozon (O₃) i jednostavni singletni kisik (¹O₂). Navedene strukture mogu lako i brzo prijeći u reaktivne radikale kisika. ROS se meĊusobno razlikuju u svojim reaktivnostima i toksiĉnosti. H₂O₂ je manje reaktivan od O₂˙ˉ, ali zato je više toksiĉan zbog svoje sposobnosti prodiranja kroz biološke membrane. Reaktivne dušikove jedinke (RNS) se odnose na molekule nastale od dušikovog monoksida (NO), primjerice: peroksinitriti (ONOOˉ), dušikov dioksid (NO₂˙) i nitritna kiselina (HNO₂). RNS za razliku od HO˙ i O₂˙ˉ imaju duži poluživot. Pri niskim koncentracijama, ROS i RNS su potrebne za proces sazrijevanja staniĉnih struktura, u sustavu obrane domaćina te u funkcijama brojnih staniĉnih signalnih sustava. U normalnom fiziološkom stanju u organizmu se održava ravnoteža izmeĊu djelovanja oksidansa i antioksidativne obrane organizma. Oksidacijski stres nastaje zbog povećane koliĉine oksidansa proizvedenih u organizmu ili funkcionalnog smanjenja sustava antioksidativne obrane. U ljudskom organizmu ROS nastaju iz molekularnog kisika djelovanjem UV zraĉenja ili procesima redukcije oksidativnih enzima. Najveća koliĉina ROS-a u obliku O₂˙ˉ nastaje svakodnevno u mitohondrijskom lancu za prijenos elektrona. Od ukupnog kisika unesenog u organizam u mitohondrijima se potroši 85-90 %. Antioksidansi su tvari koje nastoje neutralizirati štetne uĉinke ROS-a i RNS-a. Antioksidansi se dijele na: antioksidativne enzime i neenzimske antioksidanse. MeĊu najvažnijim antioksidativnim enzimima istiĉu se: superoksiddismutaza (SOD), katalaza, glutation-peroksidaza (GPRx), askorbat-oksidaza (AOx), glutation-S-transferaza (GSTs) i glutation-reduktaza (GR), dok meĊu neenzimskim antioksidansima: flavonoidi, karotenoidi, glutation, vitamin C, vitamin E i koenzim Q10.
Keywordsfree radicals oxidative stress antioxidants reactive oxygen substances (ROS) reactive nitrogen substances (RNS)
GranterSveučilište Josipa Jurja Strossmayera u Osijeku
Odjel za kemiju
PlaceOsijek
StateCroatia
Scientific field, discipline, subdisciplineNATURAL SCIENCES
Chemistry
Study programme typeuniversity
Study levelundergraduate
Study programmeChemistry
Academic title abbreviationuniv. bacc. chem.
Genreundergraduate thesis
Language Croatian
Defense date2014
Parallel abstract (English)
ROS and RNS are the terms collectively describing free radicals and other nonradical reactive derivatives also called oxidants. ROS refer to a number of chemically reactive molecules derived from O₂, whereas free radicals refers to the low molecular weight molecules with at least one unpaired electron. The most important group of free radicals are ROS which are superoxide anion or superoxide (O₂˙ˉ), hydroxyl radical (HO˙), peroxyl radical (RO₂˙), alkoxy radical (RO˙) and hydroxyl radical (OH˙). There are some ROS which are not free radicals: hydrogen peroxide (H₂O₂), hypochlorite acid (HOCl), ozone (O₃) and simple singlet oxygen (¹O₂). These ROS can easily and quickly switch to reactive oxygen radicals. ROS vary in their reactivities and toxicities. H₂O₂ is less reactive, but more toxic than O₂˙ˉ, because of its ability to penetrate biological membranes. RNS refer to molecules derived from nitrogen monoxide (NO), for example: peroxynitrite (ONOOˉ), nitrogen dioxide (NO₂˙) and nitrous acid (HNO₂). The half-lives of RNS are generally longer that HO˙ and O₂˙. At low or moderate concentrations, ROS and RNS are necessary for the maturation process of cellular structures, in the defense system of the host and in the functions of a number of cell signaling systems. In the normal physiological state, the body maintains a balance between the action of oxidants and antioxidant defense. Oxidative stress occurs due to increased amounts of oxidants produced in the body or functional reduction of antioxidant defense. In the human body ROS are formed from molecular oxygen by UV radiation or processes reducing oxidative enzymes. The largest amount of ROS in the form O₂ occurs daily in the mitochondrial electron trasport chain. Out the total body oxygen mitochondria consume 85-90 %. Antioxidants are substances that tend to neutralize the harmful effects of ROS and RNS. Antioxidants can be divided into two groups: enzymatic antioxidants and nonenzymatic antioxidants. The most important enzymatic antioxidants are superoxide dismutase (SOD), catalase, glutathioneperoxidase (GPRx), ascorbate-oxidase (AOx), glutathione-S-transferases (GSTs) and glutathione-reductase (GR), and nonenzymatic antioxidants are flavonoids, carotenoids, glutathione, vitamin C, vitamin E and coenzyme Q1 0.
Parallel keywords (Croatian)slobodni radikali oksidacijski stres antioksidansi reaktivne kisikove jedinke (ROS) reaktivne dušikove jedinke (RNS)
Resource typetext
Access conditionOpen access
Terms of usehttp://rightsstatements.org/vocab/InC/1.0/
URN:NBNhttps://urn.nsk.hr/urn:nbn:hr:182:518137
CommitterSanda Hasenay