Determination of caffeine and chlorogenic acid in coffee brews

Posljednjih godina veliko zanimanje znanstvenih istraživanja usmjereno je na kavu kao bogati izvor biološki aktivnih spojeva (polifenoli, metilksantini i melanoidini) koji zbog visokog antioksidacijskog kapaciteta pokazuju pozitivne učinke na ljudsko zdravlje. Cilj ovog istraživanja bio je odrediti kvalitativni i kvantitativni sastav polifenola i metilksantina u različito pripremljenim uzorcima kave (crne kave, kave s mlijekom i bijele kave) i instant «cappuccina» te odrediti njihov antioksidacijski kapacitet određen ABTS i FRAP metodama. Udjel ukupnih fenola i antioksidacijski kapacitet određeni su spektrofotometrijski, a kafein i klorogenska kiselina (3-CQA, 4-CQA i 5-CQA) detektirani su HPLC metodom. Najveći udjel ukupnih fenola, klorogenske kiseline i kafeina određen je u instant kavama. Dodatkom mlijeka udjel ispitivanih biološki aktivnih spojeva u svim napicima opada, a sukladno tome i antioksidacijski kapacitet. Udjel kafeina i kolorogenske kiseline značajno se povećava podgrijavanjem pripravljenih napitaka kave.In recent years, coffee beverages have been extensavely investigated, due to their high content of biologically active compounds, such as polyphenols, methylxantines and melanoidins which have been shown to posses beneficial effects on human health, owing to their strong antioxidant activity. The aim of this study was to determine the phenolic and methylxantine composition, as well as the antioxidant capacity of different coffee bewes. The content of total phenols was determined spectrophotometricaly, while the content of chlorogenic acid (3-CQA, 4-CQA and 5-CQA) and caffeine was determinated by using high preformance liquid chromatography (HPLC-PDA). Among all studied brewes, the highest content of total phenols as well as chlorogenic acid and caffeine was determinated in instant coffees which by addition of milk decreases. All beverages were screened for their potential antioxidant activities using two different radical scavening methods: ABTS and FRAP. The antioxidative capacity of the investigated coffee bevrages correlates with their phenolic content