Influence of preparation procedures on the phenolic content, antioxidant and antidiabetic activities of green and black teas

Almeida, Tânia Santos de; Araújo, Maria Eduarda Machado; Rodríguez, Lucía González; Júlio, Ana; Mendes, Beatriz Garcia; Borges dos Santos, R. M.; Simões, José Artur Martinho

http://hdl.handle.net/10400.1/12823

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Authors

Almeida, Tânia Santos de

Araújo, Maria Eduarda Machado

Rodríguez, Lucía González

Júlio, Ana

Mendes, Beatriz Garcia

Borges dos Santos, R. M.

Simões, José Artur Martinho

Abstract(s)

The influence of common tea preparation procedures (temperature, infusion time, consumption time interval and tea bag/loose-leaf) and the type of water used, on the total phenolic content (TPC), the radical scavenging activity and the alpha-glucosidase inhibitory activity were assessed. Higher TPC and antioxidant activity were obtained when using lower mineralized waters. Tea bags also evidenced higher antioxidant activity than loose-leaf samples. Under the same conditions (90 degrees C and five minutes of infusion time) green tea contains almost twice the quantity of polyphenols and the free radical scavenging ability of black tea. In the alpha-glucosidase assay all infusions were active (97-100 %). Furthermore, HPLC allowed to identify some of the polyphenols present in both teas and to monitor their composition change with time. After twenty-four hours, the antioxidant activity was maintained without significant changes, but a small decrease in enzyme inhibition was observed, although this activity was still very high.