Antioxidative capacity determination of structurally different polyphenolic compounds usin UV/VIS and spectrofluorimetric assays

Antioksidanti su spojevi koji mogu odgoditi, inhibirati ili spriječiti oksidaciju oksidabilnih spojeva različitim mehanizmima. Važnu skupinu antioksidanata čine polifenolni spojevi koji se prema strukturi mogu podijeliti na: fenolne kiseline, flavonoide, stilbene i lignine. Fenolne kiseline su jednostavni fenoli, a dijele se na hidroksibenzojeve i hidroksicimetne kiseline. Flavonoidi tvore najveću skupinu polifenola, a mogu se podijeliti u različite klase: antocijanini, flavonoli, flavanoni, flavanoli, flavoni i izoflavoni. Polifenoli pokazuju jaku antioksidacijsku aktivnost, za koju je ključna njihova struktura. U radu je istražen antioksidacijski kapacitet polifenolnih spojeva različitih struktura: flavanola ((+)-katehin, (-)-epikatehin, procijanidin B1 i procijanidin B2), flavonola (kvercetin), fenolnih kiselina (galna kiselina i sinapinska kiselina) i antocijanina (cijanin-klorid). Usporedno je istražen kapacitet askorbinske kiseline i Troloxa. Za određivanje antioksidacijskog kapaciteta primijenjene su UV/VIS spektrometrijske metode (DPPH, ABTS i FRAP) i spektrofluorimetrijska metoda (ORAC). Dobiveni rezultati pokazuju da postoji velika različitost antioksidacijskog kapaciteta između analiziranih spojeva, ovisno o njihovoj strukturi i primijenjenoj metodi.Antioxidants are compounds that can delay, inhibit or prevent the oxidation of oxidizable substrates by different mechanisms. Polyphenolic compounds are important group of antioxidants and they can be classified according to their structure: phenolic acids, flavonoids, stilbenes and lignins. Phenolic acids are simple phenols and include hydroxybenzoic acids and hydroxycinnamic acids. Flavonoids are the largest group of polyphenolic compounds and they are classified into anthocyanins, flavonols, flavanones, flavanols, flavones and isoflavones. Polyphenolics are known as powerful antioxidants and the key determinant of their activity is their structure. In this study antioxidative capacity of structurally different polyphenolic compounds was investigated: flavanols ((+)-catechin, (-)-epicatechin, procyanidin B1 and procyanidin B2), flavonols (quercetin), phenolic acids (gallic acid and sinapic acid) and anthocyanins (cyanin chloride). Antioxidative capacity of ascorbic acid and Trolox was also investigated. The antioxidative capacity was determined by using UV/VIS spectroscopy assays (DPPH, ABTS and FRAP) and fluorescence spectroscopy assay (ORAC). It was found that there is variability in antioxidative capacity among the investigated compounds, depending on their structure and the method used