RTU Research Information System
Latviešu English

Publikācija: Studies of Natural Antioxidants and Synthesis of Their Analogues

Publication Type Doctoral Thesis
Funding for basic activity Unknown
Defending: 18.12.2014 14:00, MLĶF, Paula Valdena ielā 3, 272.telpā
Publication language Latvian (lv)
Title in original language Dabīgo antioksidantu meklējumi un to analogu sintēze
Title in English Studies of Natural Antioxidants and Synthesis of Their Analogues
Field of research 1. Natural sciences
Sub-field of research 1.4 Chemical sciences
Authors Inese Mieriņa
Keywords natural antioxidants, analogues of avenanthramides, cinnamoyl anilines, anilides of 3-arylpropanoic acid, 4-arylquinolin-2(1H)-ones, 3-arylmethyl-4-hydroxyquinolin-2(1H)-ones, derivatives of coumarin-3-carboxylic acid, 3-arylmethyl-4-hydroxycoumarins, arylmethylmeldrum`s acids, quinazolin-4-ones, antiradical activity, antioxidant activity
Abstract Promocijas darbs veltīts dabas antioksidantu avenantramīdu analogu struktūras un antiradikāļu/antioksidantu aktivitātes sakarību pētījumiem. Promocijas darba literatūras apskatā apkopota informācija par vienu no jaunākajiem un pēdējos gados plašāk pētītajiem antiradikāļu darbības mehānismiem - SPLET (secīga protona atdošana un elektrona pārnese) mehānismu. Darba eksperimentālās daļas ietvaros pagatavoti auzu un miežu graudu, griķu un krūmcidoniju sēklu, upeņu sēklu, spiedpalieku un pumpuru, kā arī apiņu rogu antioksidantu ekstrakti un pārbaudīta to pielietojamība augu eļļu un to metilesteru stabilizēšanā. Sintezēti dažādi dabas antioksidantu – avenantramīdu - struktūras analogi, tostarp veiktas gan nelielas struktūras izmaiņas (aizvietotāju maiņa aromātiskajos gredzenos, kā arī dubultsaites reducēšana), gan iegūti dažādi heterocikliskie analogi – hinolīn-2(1H)-ona, hinazolīn-4-ona, kumarīna un meldrumskābes atvasinājumi. Šai sakarā izstrādātas jaunas vai optimizētas zināmās sintēzes metodes. Izmantojot 1,1-difenil-2-pikrilhidrazila un galvinoksila testus, izvērtēta visu sintezēto savienojumu antiradikāļu aktivitāte. Atrasts, ka vislabākos rezultātus uzrāda tie savienojumi, kas satur vanilīna vai sīringaldehīda fragmentu; antiradikāļu aktivitātes nodrošināšanai būtisks izrādījies arī 2-arilmetil-1,3-dikarbonilfragments. Atklāta jauna un efektīva antioksidantu klase – 5-arilmetil-1,3-dioksān-4,6-dioni. Pētīti visu sintezēto avenantramīdu analogu grupu reakciju ar brīvo radikāli DPPH mehānismi; pārbaudīta arī visu grupu pārstāvju antioksidantu aktivitāte augu eļļu un to metilesteru oksidatīvās stabilitātes nodrošināšanā. Izmantojot HF-3-21g metodi aprēķināta sintezēto savienojumu reaģētspējīgāko OH un CH saišu protonu tieksme un saites disociācijas entalpija; analizētas sakarības starp šīm vērtībām un eksperimentāli noteikto antiradikāļu/antioksidantu aktivitāti.
Abstract in English Doctoral thesis is devoted to the studies of structure-antiradical/antioxidant activity relationships of the analogues of natural antioxidants avenanthramides. The literature review focuses on one of the most recent and during the last years widely studied antiradical mechanisms – SPLET (sequential proton loss and electron transfer) mechanism. Various extracts of antioxidants have been prepared from grains of oat and barley, seeds of buckwheat and Japanese quince, seeds, pomace and buds of black currant, as well as hulls of hop; applicability of these extracts for improvement of the oxidative stability of vegetable oils (and their methyl esters) has been explored in the experimental part of thesis. Synthesis of various analogues of natural antioxidants avenanthramides has been carried out: both small modifications (variation of the substituents in the aromatic rings and hydrogenation of the double bond) and construction of heterocyclic analogues (derivatives of quinolin-2(1H)-ones, quinazolin-4-ones, coumarins and Meldrum`s acid) have been realized. The new methodologies are elaborated and known synthetic methods are optimized to reach the target compounds. All synthesized compounds have been tested for their antiradical activity using free radicals 1,1-diphenyl-2-picrylhydrazyl and galvinoxyl. It has been found out that compounds containing moiety of the vanillin or syringaldehyde possess the highest antiradical activity; the 2-arylmethyl-1,3-dicarbonyl residue has appeared essential for antiradical activity, too. The new class of effective antioxidants – 5-arylmethyl-1,3-dioxane-4,6-diones – has been discovered. The plausible mechanisms of the reaction between free radical DPPH and each group of synthesized analogues of avenanthramides are discussed. The representatives of each group of obtained antioxidants have been tested to clear up their impact on the oxidative stability of vegetable oils and their methyl esters. The proton affinity and bond dissociation enthalpy of the most reactive OH and CH bonds of synthesized compounds have been calculated by HF-3-21g method; the values of these parameters are compared with the experimentally measured antiradical/antioxidant activity.
Reference Mieriņa, Inese. Studies of Natural Antioxidants and Synthesis of Their Analogues. PhD Thesis. Rīga: [RTU], 2014. 309 p.
Summary in English
ID 19366