Comparison of the antioxidant activity of roasted tea with green, oolong, and black teas

Abstract

Although the antioxidant properties of green, oolong, and black teas have been well studied, antioxidant activity has not been examined in roasted tea. Therefore, in the current studies, we investigated the antioxidant activity of roasted tea in comparison with those of green, oolong, and black teas. Using water extracts of the various teas, we examined the total phenolic content as well as the antioxidant activities, including the reducing power, the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, and the inhibition of hemolysis caused by 2,2'-azo-bis(2-amidinopropane) dihydrochloride (AAPH)-induced lipid oxidation in erythrocyte membranes. The roasted tea contained lower levels of total phenolics than green, oolong, or black tea (green tea > oolong tea > black tea > roasted tea). The relative reducing power and DPPH scavenging activity decreased in the following order: green tea > roasted tea > oolong tea > black tea. Also, green tea was more effective against AAPH-induced erythrocyte hemolysis than other teas (green tea>roasted tea = oolong tea = black tea). These results suggest that roasted tea is beneficial to health, in humans, because of its high antioxidant activity.

Determinação da atividade antioxidante e do teor total de polifenol em amostras de chá de ervas comercializadas em sachets

“…Embora os procedimentos encontrados na literatura sejam semelhantes (variando a massa de material seco de 1,0 a 1,5 g em um volume final de água de 100-250 mL), parece não haver uma forma padronizada para a preparação de amostra de chás para a análise 5,11,30,31 . Em todas as análises do presente trabalho as amostras de chá foram preparadas com o sachet fechado da mesma forma como aquela ingerida pelo consumidor e de maneira semelhante à efetuada em outro trabalho 30 .…”

“…Além disso, o processo para embalagem da ervas nos envelopes, incluindo a possível inclusão de excipientes nas formulações dos sachets, pode levar a uma alteração significativa da atividade antioxidante 31,36,37 .…”

Effect of Extraction Conditions on Measured Total Polyphenol Contents and Antioxidant and Antibacterial Activities of Black Tea

“…Reducing powers and total polyphenols of tea extracts at 2, 8 and 18 h of extraction correlated significantly (R 2 = 0.98, 0.99 and 0.99, respectively). Satoh et al [27] also observed that there was a strong correlation between the RP and total phenolic content of different tea extracts including black tea. However, Psarra, et al [28] found a poor correlation (R 2 =0.60) between RP and total polyphenol of wines and also a high correlation (R 2 =0.81) for radical scavenging activity.…”

Identification of Date Seeds Varieties Patterns to Optimize Nutritional Benefits of Date Seeds

“…(+)-Catechin and (-)-Epicatechin contents: Determination (+)-catechin and (-)-epicatechin in date seeds extracts was performed according to the method of Satoh [16]. In brief, high-performance liquid chromatography equipped with 125 binary HPLC pump, 2475fluorescence detector, 717 plus auto sampler and inline degasser AD was used (Waters Corporation, Milford, MA., USA).…”