Isolation, Identification, and Biotransformation of Teadenol A from Solid State Fermentation of Pu-erh Tea and In Vitro Antioxidant Activity

Post-fermented Pu-erh tea (PFPT) has several health benefits, however, little is known about the bioactive compounds. In this study, a PFPT compound was isolated by column chromatography and identified as Teadenol A by spectroscopic data analyses, including mass spectrometry and 1D and 2D NMR spectroscopy. Teadenol A in tea leaves was biotransformed by Aspergillus niger and A. tamari at 28 °C for 14 d at concentrations ranging from 9.85 ± 1.17 to 12.93 ± 0.38 mg/g. Additionally, the compound was detected in 22 commercial PFPTs at concentrations ranging from 0.17 ± 0.1 to 8.15 ± 0.1 mg/g. Teadenol A promoted the secretion of adiponectin and inhibited the expression of protein tyrosine phosphatase-1B. Antioxidant assays (e.g., 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity, total antioxidant capacity (T-AOC), hydrogen donating ability, and superoxide anion radical scavenging capacity) revealed that Teadenol A has antioxidant properties. Therefore, Teadenol A is an important bio-active component of PFPT.