15C-14 |
Determination of flavonols (myricetin, quercetin and kaempferol) contents of black tea infusions |
O. TOKUSOGLU and M. K. Unal. Food Engineering Department., Ege University, 35100, Bornova,¤zmir, TURKEY., Izmir, 35100, Turkey Flavonoids are natural products widely distributed in plant foods and have a wide range of pharmaceutical properties including antioxidative, anticarcinogenic and antiarteriosclerotic. Flavonol flavonoids occur predominantly as O-glycosides with a sugar residue mostly at the C-3 position and non-glycosylated forms (aglycones). The objectives of our study were 1) the effectively quantitative determination of three widespread flavonol aglycons (myricetin, quercetin and kaempferol) in black tea infusions using High Performance Liquid Chromatography (HPLC) with UV dedection 2) the optimization of isocratic elution procedure for the determination of the hydrolysed flavonols by HPLC. Twenty-three commercial black teas (Camellia Sinensis L.), manufacturing pure black tea samples and tea bags were obtained from Turkish Tea Board Çaykur, Lipton, Ulusoy Company and Seylan black teas obtained from Hey Gıda A.Ş. in Turkey. The HPLC profiles of black tea samples were obtained after acid hydrolysis and extraction method. An optimized isocratic HPLC procedure using Hypersil-ODS column with acetonitril / phosphate buffer ( 25/75 v/v, PH 2.4) as a mobile phase and UV dedection at 266 nm was used for separation of these flavonols. Standard flavonols had linear calibration curves through the origin (R2=0.9998). The total flavonol aglycon content of different black tea infusions varied from 3,89 to 7,08 mg g-1. Individual flavonol aglycons was quantified and quercetin level was 2,216- 4,170 mg g-1 whereas kaempferol was 0,463-2,466 mg g-1 , myricetin was 0,304-0,926 mg g-1, respectively. Quercetin was the major flavonol in all black teas(p<0.01)and followed by kaempferol and myricetin (p<0.01). According to our findings,Turkish daily intake of these flavonols by the consumption of black teas was 9,35-16,99 mg/day. Black teas are excellent potential source of quercetin, kaempferol and myricetin in the human diet. The method was objective and reproducible for quantitative identification of above-mentioned flavonols in black tea infusions. .
Session 15C, Food Chemistry: Food composition and analysis
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