Determination of caffeine content in tea

Čaj je posljednjih godina postao najpopularnije piće upravo zbog svog sastava i njegovog utjecaja na zdravlje. Uz flavonoide, vitamine i minerale, najvažniji sastojak čaja je alkaloid kafein. Cilj ovog istraživanja bio je odrediti udjele kafeina u 7 različitih vrsta čajeva: bijeli, žuti, zeleni, oolong, crni, maté i prženi maté čaj. Udjeli kafeina određeni su primjenom četiri različite metode: ekstrakcija s kloroformom, mikro-metoda, metoda s olovnim acetatom i metoda tekućinske kromatografije visoke djelotvornosti (HPLC-PDA). Antioksidacijski kapacitet čajeva, kao i ekstrahiranog („sirovog“) kafeina, određen je primjenom dvije metode: reakcijom s 2,2'-azinobis(3-etilbenzotiazolin-6-sulfonska kiselina) radikalom (ABTS metoda) te reakcijom s željezo(III)-tripiridiltriazin (Fe3+-TPTZ) kompleksom (FRAP metoda). Primjenom sve četiri metode, najveći udjel kafeina određen je u bijelom čaju, dok je maté i prženi maté čaj karakteriziran najmanjim udjelom kafeina. Rezultati mikro-metode i metode s olovnim acetatom dobro koreliraju s rezultatima HPLC metode.In recent years, tea became one of the most popular beverages of the world, mainly due to the compounds it contains and its influence on human health. Along with flavonoids, vitamins and minerals, the most important tea substance is the alkaloid caffeine. The aim of this study was to determine the content of caffeine in 7 different types of tea: white, yellow, green, oolong, black, maté and roasted maté tea. The content of caffeine was determined by using four different methods: extraction with chloroform, micro-method, method with lead-acetate and high performance liquid chromatography method (HPLCPDA). The antioxidant capacity of teas as well as of the extracted („raw“) caffeine was determined by using two methods: reactions with 2`-azino-bis(3-ethylbenzothiazoline-6- sulfonic acid) radical (ABTS assay) and Ferric reducing antioxidant power (FRAP assay). By applying all four methods, the highest content of caffeine was determined in white tea, whereas maté and roasted maté tea were characterised with the lowest content of caffeine. The results of the micro-method and the method of lead-acetate have a good correlation with the results of HPLC method