ABSTRACT
-Glucosidase and lipase inhibitors play important roles in the treatment of hyperglycaemia and dyslipidemia. To identify novel naturally occurring inhibitors, a bioactivity-guided phytochemical research was performed on the pu-erh tea. One new flavanol, named (-)-epicatechin-3---coumarate (), andknown analogs (-) were isolated from the aqueous extract of the pu-erh tea. Their structures were determined by spectroscopic and chemical methods. Furthermore, the water extract of pu-erh tea and its fractions exhibited inhibitory activities against-glucosidases and lipases; compoundshowed moderate inhibitory effect against sucrase with an ICvalue of 32.5 μmol/L and significant inhibitory effect against maltase with an ICvalue of 1.3 μmol/L. Compounds,,anddisplayed moderate activity against a lipase with ICvalues of 16.0, 13.6, 19.8, and 13.3 μmol/L, respectively.
ABSTRACT
PURPOSE: This study aimed to evaluate the preventive effects of Camellia sinensis var. assamica (CSVA) on diabetic nephropathy in in vitro and in vivo models. MATERIALS AND METHODS: MDCK cells were incubated with 1 mM of oxalate with or without different concentrations of CSVA, then MTT and malondialdehyde (MDA) assays were performed to investigate the preventive effects of CSVA on oxalate-induced cytotoxicity and oxidative stress. Thirty male db/db mice were divided into three groups. Group 1 were fed AIN-93G ad libitum; group 2 were fed AIN-93G mixed with 10% fermented CSVA ad libitum; group 3 were fed AIN-93G mixed with 10% non-fermented CSVA ad libitum. The mice were sacrificed 14 weeks later, and the serum glucose level, 24-hour urine chemistry, and morphological changes in the kidneys were examined. RESULTS: As CSVA concentrations increased, viable MDCK cells increased in concentration. MDA production decreased over time in the CSVA treated group. The creatinine clearance of group 3 was lower than those of groups 1 and 2. The amount of urine microalbumin and protein in group 1 were higher than those in groups 2 and 3. Also, more glomerulus basement membrane foot processes were preserved in groups 2 and 3. CONCLUSION: In conclusion, CSVA has beneficial preventive tendencies towards diabetic nephropathy in both in vitro and in vivo models.