Xanthone glycosides from Swertia bimaculata with α-glucosidase inhibitory activity.

Seven new xanthone glycosides (1-7) were isolated from the n-butanol extract of Swertia bimaculata, together with six known compounds (8-13). Their structures were elucidated on the basis of extensive spectroscopic analyses (1D- and 2D-NMR, HRESIMS, UV, and IR) and comparison with data reported in the literature. All the compounds were evaluated for their α-glucosidase inhibitory activities in vitro, and compounds 3, 4, and 7 exhibited significant activities to inhibit α-glucosidase. Meanwhile the effects of different substitutions on the α-glucosidase inhibitory activity of xanthone glycosides from S. bimaculata are also discussed.

Polysaccharides from Liriopes Radix ameliorates hyperglycemia via various potential mechanisms in diabetic rats.

BACKGROUND: Liriopes Radix, which is regarded as both drug and healthy diet, is drunk as tea and used in traditional Chinese medicine to treat diabetes. Based on our previous studies, investigated the hypoglycemic effects and explored the mechanisms of total polysaccharides from Liriope spicata var. prolifera (Liriopes Radix) in a diabetic rat model. RESULTS: TLSP reduced hyperglycemia in diabetic rats. The oral glucose tolerance test showed that TLSP could improve the glucose tolerance of diabetic rats. Damage to liver and pancreas tissue was inhibited after treatment with TLSP. Moreover, TLSP increased glycogen content, glucokinase (GK) and glycogen synthetase (GS) activities, and suppressed the elevation of glucose-6-phosphatase (G6Pase) and glycogen phosphorylase (GP) activities in liver. Compared with the diabetic control group, GK and GS mRNA expression were significantly elevated, while G6Pase and GP mRNA expression were decreased in TLSP groups. In addition, TLSP could inhibit glycogen synthase kinase-3ß expression and increase insulin receptor, insulin receptor substrate-1, phosphoinositide 3-kinase, protein kinase B and glucose transport protein-4 expression in liver. CONCLUSION: TLSP showed hypoglycemic function. Improvement of glucose metabolism and insulin-signaling transduction were possible mechanisms.

Antidiabetic effects of Swertia macrosperma extracts in diabetic rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Swertia macrosperma is a traditional folk medicine used for its anti-hepatitis, antipyretic and antidotal effects as "Dida" or "Zangyinchen" in Tibet, Yunnan and Guizhou province for a long time, and it has been reported for its anti-diabetic effects in a Chinese patent. Swertia macrosperma was reported rich in xanthones, iridoids, seco-iridoids and their glycosides, several of which had been documented as potential antidiabetic agents. The objective of this study was to investigate the antidiabetic effect of Swertia macrosperma in diabetic rats. MATERIALS AND METHODS: This study was designed firstly to evaluate the effect of Swertia macrosperma on glucose consumption in HepG2 cells. Based on the result in HepG2 cells, the antidiabetic effect of ethanol extract (EE) and n-butanol extract (BE) were investigated in diabetic rats induced by high fat fed and streptozotocin. The effects of EE and BE on fasting blood glucose, oral glucose tolerance test, serum insulin, glycosylated hemoglobin, serum lipid level, serum antioxidant parameters, glucokinase, glucose-6-phosphatase activities and glycogen content in liver tissue were measured, histology examination of pancreatic tissue was also carried out. RESULTS: After 4 weeks treatment with EE and BE, apparently decreased fasting blood glucose concentrations were observed in these treated groups, compared with the diabetic control groups. Additionally, improvement in serum antioxidant parameters and lipid profile were evidenced clearly. Moreover, EE and BE had effects of protecting the pancreatic ß-cells and stimulating insulin secretion from the remaining pancreatic ß-cells, evidenced by pancreatic histology examination. Increased glucokinase activity and decreased glucose-6-phosphatase activity were observed in liver. CONCLUSION: The results of in vivo and in vitro experiment suggested that EE and BE of Swertia macrosperma had excellent effects on controlling the hyperglycemia and hyperlipidemia in diabetic rats.

Preventive effects of polysaccharides from Liriope spicata var. prolifera on diabetic nephropathy in rats.

This study was undertaken to investigate preventive effects of polysaccharides (LSP) from Liriope spicata var. prolifera on diabetic nephropathy in rats, which were induced by high fat-fed and low-dose streptozotocin (STZ). The levels of fasting blood glucose (FBG) and glycosylated hemoglobin (HbA1c) in diabetic rats were significantly decreased after treated with LSP for 28 days. Additional, the glucose tolerance of diabetes rats showed improvement after administration of LSP. The results also indicated that LSP were able to normalize hyperlipidemia, ameliorate oxidative stress, improve renal function parameters, inhibit the structural damages of kidney tissue and down-regulate the system of advanced glycation end products - receptor for advanced glycation end products (AGE-RAGE). In conclusion, LSP had potential preventive effects on diabetic nephropathy in diabetic rats.

In vitro and in vivo anti-diabetic activity of Swertia kouitchensis extract.

ETHNOPHARMACOLOGICAL RELEVANCE: Swertia kouitchensis has long been used as a folk medicine to treat hepatitis and diabetes in central-western China. Therefore, this study was aimed to evaluate the anti-diabetic activity of the plant ethanol extract. MATERIALS AND METHODS: Firstly, the extract was tested for its inhibitory activity on α-amylase and α-glucosidase in vitro. Following that, insulin secretion test in NIT-1 cell was performed. Then, oral sucrose or starch tolerance test of the extract were carried out in normal mice. After that, acute effect of the extract was executed in normal and streptozotocin-induced (60 mg/kg) diabetic mice. Eventually, long term effect of the extract was performed in diabetic mice for 4 weeks. Oral glucose tolerance test and biochemical parameters were estimated at the end of the study. RESULTS: Swertia kouitchensis extract could remarkably inhibit the activity of α-amylase and α-glucosidase and stimulate insulin secretion in vitro. And also the extract displayed anti-hyperglycemic activity, improved antioxidant capacity, ameliorated the hyperlipidemia and carbohydrate metabolism in diabetic mice. CONCLUSIONS: Swertia kouitchensis exhibits considerable anti-diabetic activity and metabolic alterations in diabetic mice. These results provide a rationale for the use of Swertia kouitchensis to treat diabetes mellitus.