Radikalima potaknute peroksidacije i izomerizacije nezasićenih masnih kiselina

Uzročno-posljedične veze između slobodnih radikala u biološkim sustavima i različitih patoloških stanja omogućavaju da se radijacijsko-kemijske metode koriste za pripravu i praćenje njihovih reakcija u kontroliranim uvjetima. U ovom su radu istraživani radikali višenezasićene masne kiseline, prekursori za dvije vrste procesa, peroksidaciju i, posebno u prisustvu biološki važnih tiola, cis, trans-izomerizaciju na dvostrukoj vezi linolne kiseline, LiH. Pritom je razvijen modelni sustav micela LiH u kojemu se radikalski procesi mogu selektivno pratiti u uvjetima koji se, za razliku od fizioloških uvjeta, mogu prilagođavati potrebama eksperimentiranja. Prvi put se istražila povezanost tih dvaju radikalima induciranih procesa u biomimetičkim uvjetima te je pokazano da hidroperoksidi (LiOOH) i transkonfiguracija LiH nastaju i u oksidacijskim uvjetima. Biomimetički model priređen je s dodatkom 2-merkaptoetanola kao amfifilnog tiola, a inicijacija radikalskih procesa provedena gama zračenjem s dozama zračenja do 400 Gy u različitim uvjetima. U uvjetima ravnoteže sa zrakom uz značajnu koncentraciju LiOOH (~105 mol dm3) odvijao se i proces cis, transizomerizacije s katalitičkim ciklusom 370. Kako bi se predvidio utjecaj samoorganiziranih supramolekulskih struktura LiH na ispitivane procese istražen je i utjecaj veličine micela te prisutnost prirodnih antioksidansa. The cause-effect relationship between free radicals in biological systems and the various pathological conditions enable us to use the radiation-chemical methods for preparation and determination these reactions under controlled conditions. In this paper we investigated polyunsaturated fatty acid radicals which are precursors for the two types of processes, peroxidation and, especially in the presence of biologically relevant thiol, cis, transisomerization of linoleic acid (LiH). A model micellar system was developed in which radical processes of LiH were selectively determined under conditions that, in contrast to the physiological, could be adapted to the experiments requirements. These two radical-induced processes were compared for the first time under biomimetic conditions demonstrating that hydroperoxides (LiOOH) and trans-lipids can be formed under oxidizing conditions. Biomimetic model was prepared with the addition of 2-mercaptoethanol as amphiphilic thiol, and radical processes initiation was performed by -radiation up to 400 Gy under different conditions. In air-equilibrated solutions, together with substantial amount of LiOOH (~10-5 mol dm3), the cis, trans-isomerization process was also observed with a catalytic cycle of 370. In order to envisage the impact of self-organized supramolecular organization of LiH on the outcome of lipid peroxidation and cis, trans-isomerization processes, the influence of the micelle size and the presence of natural antioxidants were also studied.