Antioxidant Activity of the Different Parts of Dokudami (Houttuynia Cordata Thunb) and the Effects of Manufacturing Processes on the Polyphenol Content, Antioxidant Activity, and Color Tone of Its Tea

Abstract

  This study examined the antioxidant activity of the different parts of the Dokudami (Houttuynia cordata Thunb) plant and the effects of manufacturing processes on the color tone of its tea. Moreover, the effects of the manufacturing process on the total polyphenol content (TPC), antioxidant activities (by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, and hydrophilic oxygen radical antioxidant capacity (H-ORAC) assay) of the Dokudami tea were elucidated. The values of the TPC and antioxidant activities of the different parts of the Dokudami plant decreased in the order of flower > leaf > petiole > stem. Furthermore, the manufacturing process had a greater impact on the a^* value of the Dokudami tea than the L^* and b^* values. TPC and antioxidant activity of the steam treated tea showed higher values than untreated and other-treated tea, while fermentation had the opposite effect. The drying method and roasting treatment were found to have a negligible effect.