Taxifolin-3-O-glucoside from Osbeckia nepalensis Hook. mediates antihyperglycemic activity in CC1 hepatocytes and in diabetic Wistar rats via regulating AMPK/G6Pase/PEPCK signaling axis.

ETHNOPHARMACOLOGICAL RELEVANCE: Osbeckia nepalensis Hook. f. is an ICMR documented plant well known for its antidiabetic uses among the folk people of Northeast Region of India. In-depth study with scientific substantiation of the plant may uphold the therapeutic potential against the treatment of type 2 diabetes mellitus (T2DM). AIM OF THE STUDY: The present study evaluates the traditionally claimed prophylactic potential of O. nepalensis and its extracts along with the isolated compound taxifolin-3-O-glucoside (TG) against the downregulation of T2DM related hepatic gluconeogenesis through in vitro, in vivo and in silico conditions as a means of ameliorating hyperglycemia. MATERIALS AND METHODS: Antidiabetic potential of O. nepalensis was carried out in both CC1 hepatocytes (in vitro) and STZ-induced diabetic male Wistar rats (in vivo). Enriched bioactive fraction and bioactive molecules were isolated through bioactivity-guided fractionation, yielding two major molecules, taxifolin-3-O-glucoside and quercitin-3-O-rhamnoside. The bioactivity of taxifolin-3-O-glucoside was validated through immunoblotting techniques aided by in silico molecular docking and simulations. RESULTS: Methanolic extract of O. nepalensis and taxifolin-3-O-glucoside (TG) isolated thereof enhanced the uptake of glucose in CC1 hepatocytes and downregulates the gluconeogenic enzymes (G6Pase and PEPCK) and its related transcription factors (FOXO1, HNF4α and PGC1α) through the stimulation of AMPK phosphorylation in in vitro condition. Moreover, in in vivo experiments, the in vitro most active fraction BuSFr1 (consisting of the two active major compounds taxifolin-3-O-glucoside and quercitin-3-O-rhamnoside) exhibited a substantial decrease in elevated blood glucose level and increase the glucose tolerance as well as plasma insulin level. In silico molecular docking and simulations for TG with the protein G6Pase inferred the docking sites and stability and showed taxifolin-3-O-glucoside as more potent and non-toxic as compared to quercitin-3-O-rhamnoside. CONCLUSION: The traditionally claimed antidiabetic effect of O. nepalensis has been proved to be effective in lowering the blood glucose level through in vitro, in vivo and in silico analysis which will pave a way for the development of antidiabetic phytopharmaceutical drugs which can be validated through further clinical studies.

Evaluation of therapeutic effect of Premna herbacea in diabetic rat and isoverbascoside against insulin resistance in L6 muscle cells through bioenergetics and stimulation of JNK and AKT/mTOR signaling cascade.

BACKGROUND: Premna herbacea Roxb., a perennial herb is well documented for its therapeutic uses among the traditional health care-givers of Assam, India. Scientific validation on the traditional use of the medicinal plant using modern technology may promote further research in health care. PURPOSE: This study evaluates the therapeutic potential of methanolic extract of P. herbacea (MEPH) against type 2 diabetes mellitus (T2DM) and its phytochemical(s) in ameliorating insulin resistance (IR), thereby endorsing the plant bioactives as effective anti-hyperglycemic agents. METHODS: The anti-diabetic potential of the plant extract was explored both in L6 muscle cells and high fructose high fat diet (HF-HFD) fed male Sprague Dawley (SD) rats. Bioactivity guided fractionation and isolation procedure yielded Verbascoside and Isoverbascoside (ISOVER) as bioactive and major phytochemicals in P. herbacea. The bioenergetics profile of bioactive ISOVER and its anti-hyperglycemic potential was validated in vitro by XFe24 analyzer, glucose uptake assay and intracellular ROS generation by flourometer, FACS and confocal microscopy. The potential of ISOVER was also checked by screening various protein markers via immunoblotting. RESULTS: MEPH enhanced glucose uptake in FFA-induced insulin resistant (IR) L6 muscle cells and decreased elevated blood glucose levels in HF-HFD fed rats. Isoverbascoside (ISOVER) was identified as most bioactive phytochemical for the first time from the plant in the Premna genus. ISOVER activated the protein kinase B/AMP-activated protein kinase signaling cascades and enhanced glucose uptake in IR-L6 muscle cells. ISOVER decreased the phosphorylation of p38 mitogen-activated protein kinase (p38MAPK) and c-Jun N-terminal kinase (JNK) and increased that of mammalian target of rapamycin (mTOR), thereby attenuating IR. However, molecular docking revealed that ISOVER increases insulin sensitivity by targeting the JNK1 kinase as a competitive inhibitor rather than mTOR. These findings were further supported by the bioenergetics profile of ISOVER. CONCLUSION: This study for the first time depicts the functional properties of ISOVER, derived from Premna herbacea, in ameliorating IR. The phytochemical significantly altered IR with enhanced glucose uptake and inhibition of ROS through JNK-AKT/mTOR signaling which may pave the way for further research in T2DM therapeutics.

In vitro and in vivo anti-diabetic and hepatoprotective effects of edible pods of Parkia roxburghii and quantification of the active constituent by HPLC-PDA.

ETHNOPHARMACOLOGICAL RELEVANCE: Parkia roxburghii G. Don. is a traditional medicinal plant and its pods are extensively used as food and medicine. It is believed by the traditional healers to have medicinal properties to treat diabetes, hypertension and urinary tract infections (Jamaluddin et al., 1994). MATERIALS AND METHODS: The methanolic extract of pods of P roxburghii and fractions were screened for their α-glucosidase and α-amylase inhibitory activity. Anti-hyperglycemic effects were studied on streptozotocin (45mg/kg b.w.) induced diabetes in albino rats (seven groups, n=7 n=6), using different doses for 14 days. Plasma glucose concentration (HbA1c) was analysed using whole blood, while SGOT, SGPT, TG, TC and uric acid were analysed using serum, employing commercial kits. Quantitative analysis of the major active constituent was carried out by HPLC-PDA. RESULTS: Bioactivity guided chemical investigation of the edible pods of P roxburghii identified sub-fraction EA-Fr 5 which significantly inhibited α-glucosidase (IC50 0.39±0.06 µgmL(-1)), reduced the blood glucose level to normal, and lowered the elevated levels of liver function enzymes SGOT and SGPT in STZ-induced diabetic rats. EA-Fr 5 was found to contain epigallocatechin gallate (1) and hyperin (2) which exhibited significantly higher α-glucosidase inhibitory potency with IC50 0.51±0.09 and 0.71±0.03µM respectively. EA-Fr 5 contained 379.82±2.90mg/g of EGCG, the major active constituent which manifests a broad spectrum of biological activities. CONCLUSION: The present investigation for the first time reports the occurrence of EGCG and hyperin in P roxburghii and substantiates the traditional use of pods of P roxburghii as dietary supplement for management of diabetes with significantly promising α-glucosidase inhibitory potency and anti-hyperglycemic as well as hepatoprotective effects.

Anti-diabetic potential of selected ethno-medicinal plants of north east India.

ETHNOPHARMACOLOGICAL RELEVANCE: Through one-to-one interaction with the traditional healers, the present study has identified 15 medicinal plant species traditionally used as remedies to control diabetes. MATERIALS AND METHODS: The methanolic extracts were screened for their α-glucosidase inhibitory activity. Hypoglycemic activity was assessed following glucose, sucrose and starch tolerance test on normal and STZ induced diabetic rats. RESULTS: Ficus cunia extract had the highest α-glucosidase inhibitory potency with IC50 1.39±0.74 µg mL(-1) followed by Schima wallichi (IC50 1.43±0.20 µg mL(-1)) and Wendlandia glabrata (IC50 1.67±0.33 µg mL(-1)). In STZ induced diabetic rat model, F. cunia and W glabrata extracts reduced blood glucose concentration to near normal up to 14 days when administered 48 h after STZ. CONCLUSION: The present study supports the traditional use of some of these medicinal plants in anti-diabetic remedies. The present study contributes to evidence for use of traditional medicine.