Total Phenols and Antioxidant Activities of Some Herbal Teas and In Vitro Bioavailability of Black Tea Polyphenols

Abstract

In recent years, studies on phenolic compounds and antioxidant activities of foods have increased due to the inverse relationship between degenerative diseases and consumption of polyphenol rich foods. To clarify the controversy related to if antioxidant activity can be supplied in vivo, the necessity for data on bioavailability of phenolic compounds are considered. The aim of the study was to determine total phenols and antioxidant activities of sage, linden flower, fresh nettle, dried nettle leaves and black tea infusions which are popular beverages in the Mediterranean region and also to evaluate antioxidant activities of standard phenolic compounds (catechin, ferulic acid, quercetin) and Trolox for comparison. Moreover, another goal was to determine in vitro bioavailability of black tea. Both black tea infusion and black tea dialysate inhibited ABTS radical cation oxidation by 99.43% and 42% respectively. Infusions of sage, linden flower, fresh nettle, dried nettle leaves inhibited ABTS radical cation oxidation by 39.61%, 96.70%, 70.80% and 95.50% respectively. Although total phenols of black tea dialysate decreased by 96.48%, total antioxidant activity decreased by 57.76%. Ten ?M catechin and 10?M quercetin showed 100% inhibition on ABTS radical cation oxidation. However, Trolox and ferulic acid showed 100% inhibition at 20 ?M concentrations. Total antioxidant activity of a cup of black tea was found to be equal to 10 µM of quercetin, 10 µM of catechin, 20 µM of Trolox and 20 µM of ferulic acid. Total antioxidant activity of black tea dialysate was slightly higher than both 5 ?M of Trolox and 5 ?M of ferulic acid.

Keywords

• Black tea, sage, linden flower, fresh nettle, dried nettle leaves, black tea dialysate, total phenol

Bazı Bitkisel Çayların Toplam Fenolik Madde İçerikleri, Antioksidan Aktiviteleri ve Siyah Çay Polifenollerinin in vitro Biyoyararlılığı

Öz

Son yıllarda fenolik bileşikler ve gıdaların antioksidan aktiviteleri üzerine yapılan çalışmaların sayısındaki artış, polifenollerce zengin gıdaların tüketimi ile dejeneratif hastalıklar arasında negatif ilişkinin saptanmasına bağlanmaktadır. Bu ilişkinin in vivo koşullarda sağlanıp sağlanamayacağını açıklığa kavuşturmak için fenolik bileşiklerin biyoyararlılığına ait çalışmalara gereksinim olduğu belirtilmektedir. Bu çalışmanın amacı Akdeniz Bölgesinde popüler olarak tüketilen adaçayı, ıhlamur, ısırgan otu, kurutulmuş ısırgan out ve siyah çayın toplam fenolik madde konsantrasyonları ile antioksidan aktivitelerini saptamak ve standart fenolik bileşikler (kateşin, ferulik asit, kuersetin) ile Troloksun antioksidan aktiviteleriyle karşılaştırmaktır. Çalışmanın bir diğer amacı ise siyah çaydaki fenolik bileşiklerin in vitro biyoyararlılığının belirlenmesidir. Siyah çay ve siyah çay dializatının ABTS radikal oksidasyonu üzerine inhibisyonları sırasıyla % 99.43 ve % 42 olarak saptanmıştır. Adaçayı, ıhlamur, ısırgan otu ve kurutulmuş ısırgan otu ile elde edilen çaylar ise ABTS radikal oksidasyonunu sırsıyla %39.61, % 96.70, %70.80 ve %95.50 düzeylerinde inhibe etmişlerdir. Siyah çay dializatının toplam fenolik madde içeriğindeki azalma % 96.48 olmasına rağmen toplam antioksidan aktivitedeki azalma % 57.76 olarak saptanmıştır. On ?M kateşin ve 10 ?M kuersetin ABTS radikal oksidasyonunu %100 inhibe etmiş, oysa Troloks ve ferulik asit için aynı inhibisyon 20 ?M konsantrasyonda saptanmıştır. Bir fincan çayın toplam antioksidan aktivitesi 10?M kuersetin, 10?M kateşin, 20 ?M Troloks ve 20 ?M ferulik aside eşdeğer bulunmuştur. Siyah çay dializatının toplam antioksidan aktivitesi ise 5 ?M Troloks ve 5 ?M ferulik asitten biraz düşük olmuştur.

Anahtar Kelimeler

• Siyah çay, adaçayı, ıhlamur, ısırgan otu, kurutulmuş ısırgan otu, siyah çay dializatı,toplam fenoller, in vitro biyoyararlılık, toplam antioksidan aktivite

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