The phenolic composition and antioxidative capacity of white and green tea prepared at different extraction conditions

U ovom radu ispitana je učinkovitost različitih otapala (voda, smjesa vode i limuna, 10%-tni, 40%-tni i 70%-tni etanol) na ekstrakciju ukupnih polifenola i flavonoida iz listova bijelog i zelenog čaja ("rinfuzni" oblik i filter vrećica) nakon različitog trajanja ekstrakcije (5, 15 i 30 minuta) te antioksidacijski kapacitet dobivenih ekstrakata. Zeleni čaj je bogatiji izvor fenolnih spojeva u usporedbi s bijelim čajem, premda učinkovitost ekstrakcije tih spojeva uvelike ovisi o duljini trajanja ekstrakcije i korištenom otapalu. Na ekstrakciju katehina iz zelenog čaja značajno utječe oblik čaja (filter vrećica ili "rinfuza"), dok se taj učinak nije pokazao statistički značajnim kod bijelog čaja. Ekstrakcija fenola vodom iz listova bijelog čaja može se ubrzati dodatkom limunovog soka. Meñu ispitivanim otapalima, 40%-tni etanol je najučinkovitije otapalo tijekom produljene ekstrakcije (30 min) katehina, posebice epigalokatehin galata.In this study efficiency of different solvents (water, mixture of water and lemon juice, 10, 40 and 70% ethanol) in extraction of total polyphenols and flavonoids from leaves of white and green tea (bagged and loose form) after different extraction time (5, 15, 30 min) and antioxidative capacity of obtained extracts were investigated. Green tea is richer source of phenolic compounds compared to white tea, but extraction efficiency of these compounds strongly depend on time of extraction and solvents used. The extraction efficiency of catechins from green tea was significantly affected by form (bagged or loose) of tea used, whereas this effect was not shown to be statistically significant for white tea. The extraction of phenolic compounds from white tea leaves by water could be accelerated by adding of lemon juice. 40% ethanol is the most effective among solvents tested in prolonged extraction (30 min) of catechins, especially in extraction of epigallocatechin gallate (EGCG). The antioxidative capacity of the investigated tea extracts correlates with their phenolic content