The composition of poliphenols and antioxidant activity of various sorts of tea

Čaj je sve češće konzumiran napitak, bilo zbog organoleptičkih svojstava, stimulirajućeg učinka ili pak potencijalnih zdravstvenih učinaka. Cilj ovog rada bio je analizirati sastav polifenola i antioksidativnu aktivnost čajeva od kamilice i lipe, kao češće konzumiranih čajeva, u odnosu na neke manje poznate čajeve, prisutne i na hrvatskom tržištu, kao što su bijeli čajevi, Oolong i rooibos. Promjene udjela ukupnih fenola i flavonoida ovisno o različitim uvjetima pripreme čajeva (temperatura i duljina trajanja ekstrakcije, višestruko ponavljanje ekstrakcija istog uzorka) praćene su spektrofotometrijskim metodama, dok su udjeli pojedinačnih fenolnih sastojaka i metilksantina određeni primjenom metoda tekućinske kromatografije visoke djelotvornosti (HPLC). Rezultati istraživanja pokazali su da se povišenjem temperature povećavao udio ukupnih fenola i flavonoida, dok se višestrukim ponavljanjem ekstrakcija istog uzorka udio istih smanjivao. Kod većine uzoraka udio ukupnih i pojedinačnih polifenolnih sastojaka i metilksantina povećavao se s duljinom trajanja ekstrakcije te je tek nakon ekstrakcije dulje od trideset minuta uslijedilo njihovo smanjivanje. Najveći udio flavan-3-ola određen je u bijelom čaju Silver Needle, dok su u čaju od kamilice najviše bile zastupljene fenolne kiseline. Metilksantini (kafein, teobromin, teofilin) su detektirani u svim ispitivanim čajevima, osim rooibosa čiji sastav karakterizira prisustvo flavona. U cilju dobivanja što objektivnijih podataka, antioksidativna aktivnost se odredila primjenom dviju metoda: reakcijom s 1,1-difenil-2-pikrilhidrazil radikalom (DPPH) i 2,2'-azino-bis(3-etilbenzotiazolin-6-sulfonskom kiselinom) (ABTS- radikal).Consumption of tea is continuously increases, whether because of its organoleptical traits, stimulating effects or potential health benefits. Therefore, the aim of this paper was to analyse polyphenolic content and antioxidant activity of camomile and linden teas, which are more often consumed, in relation to some other, less known teas, which are present at Croatian market, such as white teas, Oolong and rooibos. In order to monitor changes of the total phenolic and flavonoid content related to different conditions of tea preparation (temperature and duration of extraction, sample multiple-iteration extraction) spectrophotometry methodes were used, while the content of specific phenolic compounds and methilxanthines using the High Performance Liquid Chromatography (HPLC) were detected. Results of investigation showed that total phenolic and flavonoids content increases with the temperature increase and declines with the sample multiple-iteration extractions. Most of the samples showed increase of total and specific polyphenolic and methylxanthine content with the duration of extraction and decline after thirty minutes of extraction. The major content of flavan-3-ol was determined in white tea Silver Needle, while in the camomile tea phenolic acid as the most abundant polyphenols was detected. Methylxanthines (coffein, theobromine, theophyilline) were detected in all examine teas, except rooibos whose composition characterized the present of flavones. In order to obtain more objective data, antioxidant activity was determined by using two methodes: reaction with 1,1-diphenyl-2-picrylhydrazyl hydrate radical (DPPH) and with 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS radical)