Antioxidant Phenolic Compounds from Pu-erh Tea

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.

Flavonoid glycosides from the aerial parts of Acacia pennata in Myanmar

“…A broad singlet d H 4.99 (H-2) of the lower flavan-3-ol skeleton indicated a 2,3-cis configuration (De Mello et al, 1996). Therefore, the lower unit was elucidated to be (À)-epiafzelechin-3-O-gallate (Zhang et al, 2012). The HMBC correlation of d H 4.79 (H-4) to d C 155.1 (C-7 00 ), 112.8 (C-8 00 ) and 154.9 (C-9 00 ) established a (4 ?…”

Study of aroma formation and transformation during the manufacturing process of Biluochun green tea in Yunnan Province by HS‐SPME and GC‐MS

“…Although only about 4.94% to 8.26% unsaturated hydrocarbons were detected, these compounds were the key compounds to the flavour . Aldehydes and ketones also contributed to the flavour of tea . Potent odorants of most aldehydes and ketones were floral, honey‐like, fatty, meaty and fruit‐like .…”

“…22 Aldehydes and ketones also contributed to the flavour of tea. 23 Potent odorants of most aldehydes and ketones were floral, honey-like, fatty, meaty and fruit-like. 24,25 Taken together, drying on the caldron-type water-removing machine during manufacture played an important role in the accumulation of aroma compounds.…”

Metabolic Changes during the Pu‐erh Tea Pile‐Fermentation Revealed by a Liquid Chromatography Tandem Mass‐Spectrometry‐Based Metabolomics Approach

“…The content decrease of kaempferol combined with the level decrease of EGCG and ECG, α‐glucosidase inhibitors, aggravated the content decrease of kaempferol‐3‐glucoside. Although their contents decreased during the pile‐fermentation stage, these phenolic compounds still contribute to the radical scavenging activity of ripened pu‐erh tea (Zhang and others ).…”