Hai Ming Zhang ^1,2, Cheng Fang Wang ¹, Sheng Min Shen ³, Gang Li Wang ⁴, Peng Liu ⁵, Zi Mu Liu ¹, Yong Yan Wang ¹, Shu Shan Du ^1,*, Zhi Long Liu ^6,* and Zhi Wei Deng ⁵

¹ State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China;

² China Academy of Chinese Medical Sciences, Beijing 100700, China;

³ Qingdao Huaren Pharmaceutical Co., Ltd., Qingdao 266101, China;

⁴ National Institutes for Food and Drug Control, Beijing 100050, China;

⁵ Analytical and Testing Center, Beijing Normal University, Beijing 100875, China;

⁶ Department of Entomology, China Agricultural University, Haidian District, Beijing 100193, China.

 

Abstract: Eight compounds were isolated from the water extract of Pu-erh tea and their structures were elucidated by NMR and MS as gallic acid (1), (+)-catechin (2), (−)-epicatechin (3), (−)-epicatechin-3-O-gallate (4), (−)-epigallocatechin-3-O-gallate (5), (−)-epiafzelechin-3-O-gallate (6), kaempferol (7), and quercetin (8). Their in vitro antioxidant activities were assessed by the DPPH and ABTS scavenging methods with microplate assays. The relative order of DPPH scavenging capacity for these compounds was compound 8 > compound 7 > compound 1 > compound 6 > compound 4 ≈ compound 5 > compound 2 > VC (reference) > compound 3, and that of ABTS scavenging capacity was compound 1 > compound 2 > compound 7 ≈ compound 8 > compound 6 > compound 5 > compound 4 > VC (reference) > compound 3. The results showed that these phenolic compounds contributed to the antioxidant activity of Pu-erh tea.

 

Keywords: Pu-erh tea; DPPH˙; ABTS˙⁺; chemical constituent; antioxidant activity.