Modification of bioactive compounds in yellow tea depending of extraction condition

U ovom radu je ispitan utjecaj različitih otapala (voda, 10%-tni, 25%-tni, 50%-tni, 75%-tni i 100%-tni etanol) na udio polifenola i alkaloida u ekstraktima žutog čaja (rinfuzni oblik, filter vrećica i kuglica) pripremljenim tijekom tri ponovljene ekstrakcije, te tijekom jednodnevnog stajanja pripremljenih ekstrakata (1, 2, 4, 6, 24 sata) na sobnoj temperaturi. Također je uspoređena klasična ekstrakcija s vodom i 75%-tnim etanolom s ekstrakcijom istim otapalima u kombinaciji s ultrazvučnom kupelji. Kao najučinkovitije otapalo za ekstrakciju epigalokatehingalata (EGCG), kao najznačajnijeg katehina čaja, pokazao se 50%- tni etanol, neovisno o obliku čaja. Za ekstrakciju kafeina, kao najznačajnijeg alkaloida čaja, u rinfuznom obliku kao najučinkovitije otapalo pokazao se 25 %-tni etanol, dok kod kuglice i filter vrećice je to 50%-tni etanol. Kao najneučinkovitije otapalo za ekstrakciju istraživanih spojeva pokazao se 100%-tni etanol. Primjena ultrazvučne kupelji nije utjecala na povećanu ekstrakciju polifenola i alkaloida.In this study, the effect of different solvents (water, 10, 25, 50, 75 and 100% ethanol) on the content of polyphenols and alkaloids of yellow tea (loose form, bagged and tea ball) during multiple extraction and diferent storage time (1, 2, 4, 6 and 24 hours) at room temperature was investigated. Also classical extraction with water and 75% ethanol to the application of ultrasound bath with same solvents was compared. As the most effective extract solvent for EGCG, as the most important tea catechin, was a 50% ethanol. For the extraction of caffeine, which is the most important tea alkaloid, in loose leaf form, 25% ethanol was the most effective solvent, while 50% ethanol was the most effective solvent in bagged and tea ball form. The worst solvent for the extraction of the investigated compounds was 100% ethanol. The use of ultrasound bath did not result with increased bonus rate of extracted polyphenols and alkaloids