Ultrasound-assisted extraction of polyphenols from yellow tea

Cilj istraživanja bio je odrediti udio ukupnih fenola i antioksidacijski kapacitet u čaju. Žuti čaj u rinfuzi ekstrahiran je vodom i 75 %-tnim etanolom uz primjenu ultrazvuka amplitude 25 %, 50 %, 75 % i 100 % u trajanju od 3, 5, 10, 15 i 30 minuta. Također su pripremljeni vodeni i 75 %-tni etanolni ekstrakti, kombinacijom navedenih amplituda ultrazvuka i ponovljenih ekstrakcija istog uzorka tijekom 3 minute. Antioksidacijski kapacitet određen je primjenom tri metode: reakcija s 1, 1- difenil- 2- pikrilhidrazil (DPPH), reakcija s 2, 2'- azinobis(3- etilbenzotiazolin- 6- sulfonska kiselinom) (ABTS), te reakcija sa željezo(III)- tripiridiltriazinom (FRAP). Najveći udio fenola određen je u čaju ekstrahiranom vodom uz primjenu ultrazvuka 50 %-tne amplitude tijekom 30 minuta, a najmanji u čaju ekstrahiranom vodom uz primjenu ultrazvuka 100 %-tne amplitude tijekom 3 minute (3. ekstrakcija). Najveći antioksidacijski kapacitet izmjeren je u čaju ekstrahiranom 75 %-tnim etanolom uz primjenu 50 %-tne amplitude tijekom 30 minuta, a najmanji u trećem vodenom ekstraktu pripremljenim primjenom ultrazvuka 75 %-tne amplitude.The purpose of this research was to determine the total polyphenol content and antioxidant capacity in tea. The yellow tea in loose leaf form was extracted with water and 75% ethanol using ultrasound amplitudes of 25 %, 50 %, 75% and 100 % lasting 3, 5, 10, 15 and 30 minutes. In addition, water and 75 % ethanol extracts were prepared using the aforementioned ultrasound amplitudes and multiple extractions during 3 minutes.The antioxidant capacity was determened using three methods: DPPH (reduction of (1, 1-diphenyl-2- picrylhydrazyl), ABTS (reaction of 2,2-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) and FRAP (reaction with iron(III)tripyridyiltriazine).The highest polyphenol content is determined in tea extracted with water using 50% amplitude ultrasound during 30 minutes and the lowest in water extracted tea using 100% amplitude ultrasound during 3 minutes (third extraction). The highest antioxidant capacity was measured in tea extracted with 75% ethanol using 50% amplitude during 30 minutes and the lowest in the third water extract prepared using 75% amplitude ultrasound