Antioxidant activity of phenolics: interaction between hydroxybenzoic acid derivatives : bachelor thesis

Posljednjih godina sve više raste interes znanstvenika za fenolne spojeve zbog njihove dokazane biološke aktivnosti koja ih čini zanimljivima farmaceutskoj, kozmetičkoj i prehrambenoj industriji. U ovom završnom radu zadatak je bio odrediti antioksidacijsku aktivnost pet hidroksibenzojevih kiselina, i to galne, vanilinske, protokatehinske, siriginske i gentisinske kiseline, FRAP metodom. Osim čistih spojeva testirane su ekvimolarne smjese navedenih fenolnih kiselina pri različitim koncentracijama (50, 100, 1000 μM) u kojima su bile kombinacije dvije, tri, četiri te svih pet spojeva. Eksperimentalno dobivene redukcijske aktivnosti smjesa su uspoređene sa izračunatim teoretskim vrijednostima te je na taj način dokazano postojanje aditivnog, sinergijskog ili antagonističkog učinka. Zaključeno je kako interakcija i učinak fenolnih spojeva u smjesama uvelike ovisi o koncentracijama u kojim su navedeni spojevi prisutni. Najveću sinergiju je pokazala smjesa protokatehinske, siriginske i gentisinske kiseline pri koncentraciji od 100 µM dok je pri istoj koncentraciji najveći antagonizam pokazala smjesa vanilinske i protokatehinske kiseline.In last few years, there has been a growing interest in phenolic compounds due to their biological activities which make them interesting to the pharmaceutical, cosmetic and food industries. The aim of this work was to determine antioxidant activity of five hydroxybenzoic acids; gallic, vanillic, protocatechuic, syringic and gentisic acid using the FRAP assay. Besides pure phenolic compounds, the equimolar mixtures of the investigated acids were also tested at different concentrations (50, 100, 1000 μM) as well as combinations of two, three, four and all five acids. The experimental results were compared with the theoretical values, thus proving the existence of an additive, synergistic or antagonistic effect. It can be concluded that interaction of investigated phenolic compounds depends on concentrations in which the compounds are present. The highest synergy effect was observed for the mixture of protocatechuic, syringic and gentisic acid at concentration of 100 μM while the highest antagonism was detected for the mixture of vanillic and protocatechuic acid at same concentration