Effect of herbal hypoglycemic agents on oxidative stress and antioxidant status in diabetic rats

Pharmacological evaluation of medicinal plants with antidiabetic activities in Ethiopia: A review

Diabetes mellitus is a serious, chronic disease that occurs either when the pancreas does not produce enough insulin, or when the body can't effectively use insulin. Herbal medicines have been commonly used by diabetic patients for the treatment of diabetes mellitus. To include findings from different studies, publications related to in vivo and invitro antidiabetic activities of medicinal plants in Ethiopia were searched from different databases, such as Web of Science, Google Scholar, Medline, Scopus, and PubMed, using English key terms. Different medicinal plant parts were used experimentally for antidiabetic effects in Ethiopia. Among these, leaves (69%) were the most commonly investigated medicinal plant parts followed by roots (14%) and seeds (7%). Most of the investigations were completed with hydro-methanolic extracts to obtain a higher percentage of yield. Medicinal plants such as Thymus schemperi R, Thymus vulgaris L, Hagenia abyssinica, Aloe megalacantha baker, Aloe moticola Reyonolds, Aloe pulecherrima Gilbert & sebseb, Bersama abyssinica fresen, and Rubus Erlangeri Engl have shown in vitro α-amylase inhibitory activity. However, only Hagenia abyssinica, Thymus schemperi R, and Thymus vulgaris L have exhibited α-glucosidase inhibitory activity. Likewise, only the extract of Aloe pulecherrima Gilbert & sebseb posses’ maltase and sucrose inhibitory activity. In vivo antidiabetic activity were conducted for the extract of medicinal plants such as A. remota, S. rebaudiani, T. schemperi, T. vulgaris, H. abyssinica, C. aurea, D. stramonium, A. megalacantha, A. moticola, A.integrifolia, A. pulecherrima, B. grandiflorum, B. abyssinica, P. schimperiana, M. stenopetala, C. aure, J. schimperiana, T. brownie, C. macrostachys, I. spicata, O. integrifolia, C. abyssinica, R. Erlangeri, L. culinaris, A. camperi, A. polystachyus, A. ilicifalius, C. tomentosa, and C. Edulis. This review gives collective evidence on the potential antidiabetic activities of medicinal plants in Ethiopia. Moreover, further studies are recommended to substantiate the use of these medicinal plants as an antidiabetic agent.

The safety and efficacy of Momordica charantia L. in animal models of type 2 diabetes mellitus: A systematic review and meta-analysis

Type 2 diabetes mellitus is a chronic hyperglycemic condition due to progressively impaired glucose regulation. Momordica charantia L. could potentially improve hyperglycemia because its fruit extracts can alleviate insulin resistance, beta-cell dysfunction, and increase serum insulin level. We evaluated the effect of M. charantia L. in comparison with a vehicle on glycemic control in animal models of type 2 diabetes mellitus. MEDLINE, Web of Science, Scopus, and CINAHL databases were searched without language restriction through April 2019. About 66 studies involving 1861 animals that examined the effect of M. charantia L. on type 2 diabetes mellitus were included. Fruits and seed extracts reduced fasting plasma glucose (FPG) and glycosylated hemoglobin A1c in comparison to vehicle control: (42 studies, 815 animals; SMD, -6.86 [95% CI; -7.95, -5.77], 3 studies, 59 animals; SMD; -7.76 [95% CI; -12.50, -3.01]) respectively. Also, the extracts have hepato-renal protective effects at varying doses and duration of administration. Despite the observed significant glycemic control effect, poor methodological quality calls for future researches to focus on standardizing extract based on chemical markers and adopt measures to improve the quality of preclinical studies such as sample size calculation, randomization, and blinding.

Molecular approach to identify antidiabetic potential of Azadirachta indica

BACKGROUND

Azadirachta indica (Neem) is a medicinal plant, used in Ayurveda for treating various diseases, one of which is diabetes mellitus. It is known to possess antiinflammatory, antipyretic, antimicrobial, antidiabetic and diverse pharmacological properties. However, the molecular mechanism underlying the effect of A. indica on insulin signal transduction and glucose homeostasis is obscure.

OBJECTIVE

The aim was to study the effects of A. indica aqueous leaf extract on the expression of insulin signaling molecules and glucose oxidation in target tissue of high-fat and fructose-induced type-2 diabetic male rat.

MATERIALS AND METHODS

The oral effective dose of A. indica leaf extract (400 mg/kg body weight [b.wt]) was given once daily for 30 days to high-fat diet-induced diabetic rats. At the end of the experimental period, fasting blood glucose, oral glucose tolerance, serum lipid profile, and the levels of insulin signaling molecules, glycogen, glucose oxidation in gastrocnemius muscle were assessed.

RESULTS

Diabetic rats showed impaired glucose tolerance and impairment in insulin signaling molecules (insulin receptor, insulin receptor substrate-1, phospho-IRS-1(Tyr632), phospho-IRS-1(Ser636), phospho-Akt(Ser473), and glucose transporter 4 [GLUT4] proteins), glycogen concentration and glucose oxidation. The treatment with A. indica leaf extract normalized the altered levels of blood glucose, serum insulin, lipid profile and insulin signaling molecules as well as GLUT4 proteins at 400 mg/kg b.wt dose.

CONCLUSION

It is concluded from the present study that A. indica may play a significant role in the management of type-2 diabetes mellitus, by improving the insulin signaling molecules and glucose utilization in the skeletal muscle.

Potential anticancer properties of bioactive compounds of Gymnema sylvestre and its biofunctionalized silver nanoparticles

BACKGROUND

Gymnema sylvestre is an ethno-pharmacologically important medicinal plant used in many polyherbal formulations for its potential health benefits. Silver nanoparticles (SNPs) were biofunctionalized using aqueous leaf extracts of G. sylvestre. The anticancer properties of the bioactive compounds and the biofunctionalized SNPs were compared using the HT29 human adenoma colon cancer cell line.

METHODS

The preliminary phytochemical screening for bioactive compounds from aqueous extracts revealed the presence of alkaloids, triterpenes, flavonoids, steroids, and saponins. Biofunctionalized SNPs were synthesized using silver nitrate and characterized by ultraviolet-visible spectroscopy, scanning electron microscopy, energy-dispersive X-ray analysis, Fourier transform infrared spectroscopy, and X-ray diffraction for size and shape. The characterized biofunctionalized G. sylvestre were tested for its in vitro anticancer activity against HT29 human colon adenocarcinoma cells.

RESULTS

The biofunctionlized G. sylvestre SNPs showed the surface plasmon resonance band at 430 nm. The scanning electron microscopy images showed the presence of spherical nanoparticles of various sizes, which were further determined using the Scherrer equation. In vitro cytotoxic activity of the biofunctionalized green-synthesized SNPs (GSNPs) indicated that the sensitivity of HT29 human colon adenocarcinoma cells for cytotoxic drugs is higher than that of Vero cell line for the same cytotoxic agents and also higher than the bioactive compound of the aqueous extract.

CONCLUSION

Our results show that the anticancer properties of the bioactive compounds of G. sylvestre can be enhanced through biofunctionalizing the SNPs using the bioactive compounds present in the plant extract without compromising their medicinal properties.

Effect of lower doses of vanadate in combination with Azadirachta indica leaf extract on hepatic and renal antioxidant enzymes in streptozotocin-induced diabetic rats

The present study was undertaken to investigate short-term (21 days) effects of oral administration of Azadirachta indica leaf extract and vanadate, separately and in combination, on the activities of antioxidant enzymes in streptozotocin-induced diabetic rats. Vanadate is a remarkable antidiabetic agent and shows insulin mimetic effect. However, severe toxicity is associated with vanadate when used in high concentration while at lower concentration the hypoglycemic property of vanadate is reduced. So, we used a low dose of vanadate in combination with A. indica leaf extract and evaluated their effect on the antioxidant defense system. Streptozotocin-diabetic rats were treated separately with insulin, vanadate (0.6 mg/ml), A. indica, and with combined dose of vanadate (0.2 mg/ml) and A. indica. At the end of the experiment, rats were sacrificed and serum glucose levels and activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase were determined in cytosolic fraction of liver and kidney. Diabetic rats showed hyperglycemic condition and alteration in antioxidant enzyme activities. Treatment with antidiabetic compounds resulted in the reduction of glucose levels and restoration of enzyme activities to normal. Results showed that combined treatment of vanadate and A. indica leaf extract was the most effective in normalizing altered antioxidant enzyme system.

Strengthening of antioxidant defense by Azadirachta indica in alloxan-diabetic rat tissues

BACKGROUND

Azadirachta indica has been reported to correct altered glycaemia in diabetes.

OBJECTIVE

The aqueous extract of A. indica leaf and bark has been evaluated for its effect on antioxidant status of alloxan diabetic rats and compared with insulin treatment.

MATERIALS AND METHODS

The oral effective dose of A. indica leaf (500 mg/kg body weight) and A. indica bark (100 mg/kg body weight) were given once daily for 21 days to separate groups of diabetic rats. At the end of the experimental period blood glucose level and activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G-6-PD), and membrane lipid peroxidation were determined in different fractions of liver and kidney tissues.

RESULTS

Diabetic rats showed high blood glucose (P<0.01), increased level of malondialdehyde (P<0.05) and a significant decrease in the activity of antioxidant enzymes. Treatment with insulin, A. indica leaf extract (AILE), and A. indica bark extract (AIBE) restored the above altered parameters close to the control ones.

CONCLUSIONS

Both AILE and AIBE were found significantly effective in reducing hyperglycemia-induced oxidative stress. The findings suggest further investigations for the possible use of A. indica as alternative medicine to prevent long-term complications of diabetes.

Antidiabetic effect of S-allylcysteine: effect on thyroid hormone and circulatory antioxidant system in experimental diabetic rats

OBJECTIVE

It is considered that diabetes mellitus and thyroid disease are the two common endocrine disorders and also suggested that insulin and thyroid hormones influence each other actions. The present study was designed to investigate the effect of the administration of S-allylcysteine (SAC), a sulfur containing amino acid derived from garlic on blood glucose, insulin, HbA1C, total protein, albumin, Thyroid hormone (T3, T4), TSH, TBARS and circulatory antioxidant levels (SOD, CAT, GSH and GPx) in STZ-induced diabetic rats.

METHODS

SAC was administered orally for 45 days to control and STZ induced diabetic rats. The effects of SAC on glucose, plasma insulin, HbA1C, total protein, albumin, Thyroid hormone, TSH and circulatory antioxidant levels were studied.

RESULTS

The levels of glucose, TBARS, hydroperoxide and HbA1C were increased significantly whereas the levels of plasma insulin, reduced glutathione, superoxide dismutase, catalase, GSH, GPx, total protein, albumin, Thyroid hormone and TSH were decreased in STZ induced diabetic rats. Administration of SAC to diabetic rats showed a decrease in plasma glucose, TBARS, hydroperoxide and HbA1C. In addition, the levels of plasma insulin, SOD, CAT, GPx, GSH, total protein, albumin, Thyroid hormone and TSH were increased in SAC treated diabetic rats. The effect of SAC was compared with gliclazide, a well-known antioxidant and antihyperglycemic drug.

CONCLUSION

From these findings, it is indicated that SAC might be acting through activation in the synthesis and/or secretion of circulating thyroid hormones which in turn stimulate the synthesis of insulin.

Synergistic antidiabetic activity of Vernonia amygdalina and Azadirachta indica: biochemical effects and possible mechanism

ETHNOPHARMACOLOGICAL RELEVANCE

A decoction from a combination of herbs is commonly used in Traditional African Medicine for the management of chronic ailments. In Nigeria, the leaves of Vernonia amygdalina Del. (VA) and Azadirachta indica A. Juss (AI) are used traditionally as a remedy against diabetes mellitus for which empirical evidence attests to its efficacy.

AIM OF THE STUDY

To evaluate the synergistic antidiabetic action of VA and AI, the biochemical effects and possible mechanism in streptozotocin-induced diabetic rat (SDR) models.

MATERIALS AND METHODS

Ethanolic extracts of VA and AI were co-administered (200 mg/kg, 50:50) to non-diabetic rats (NDRs) and SDRs for 28 days. Blood glucose and body weight were monitored during this period, and at end of treatment, serum glucose, insulin, triiodothyronine (T3), tetraiodothyronine (T4) and α-amylase activity were studied. Glucose and activities of antioxidant enzymes, e.g., catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase (SOD), were estimated in hepatocytes, along with the impact on the histology of the liver and pancreas. Medium acting insulin, HU (5 IU/kg, s.c.) was used as a positive control.

RESULTS

The study reveals that compared with single extracts, the combined extract (VA/AI) promptly lowered blood glucose and maintained a relatively steady level over the study period, in tandem with HU. During this period, body weight gain successively increased. In SDRs, fasting blood glucose at days 0 and 28 was raised by 4.33 and 3.16 fold, respectively, and the serum glucose was raised by 7.70 fold vs. normal control (P<0.05). The discrepancies in the individual effects of VA and AI on hepatic glucose and α-amylase activity were also restored. In NDRs, VA/AI lowered blood and serum glucose (1.14 and 1.94 fold, respectively), although to a lesser extent when compared with HU. Furthermore, VA/AI was found to lower serum insulin, T3 and T4 by 1.66, 1.57 and 2.16 fold, respectively, in SDR (P<0.05). This was similar to HU, which demonstrated 1.79 and 1.68 fold reduction of insulin and T3, respectively (P<0.05), but had no effect on T4. Conversely, in NDRs, VA/AI caused 1.32, 4.93 and 1.04 fold increase in insulin, T3 and T4, respectively, reciprocal to its effect on blood and serum glucose. Oxidative stress in SDR, characterised by decreased GPx and CAT activities, was ameliorated, as the activities of the enzymes and SOD increased following a 28-day treatment with VA/AI (P<0.05). The features of diabetic pathology, indicated in the histology of the liver and pancreas, were reversed. However, the extent of recovery was partial with VA, better with AI, and distinct and total with VA/AI, compared with a null effect by HU.

CONCLUSION

Taken together, our results contribute towards validation of enhanced antidiabetic efficacy of VA and AI when combined. This synergy may be exerted by oxidative stress attenuation, insulin mimetic action and β-cell regeneration.

Biochemical evaluation of the protective effect of Aegle marmelos (L.), Corr. leaf extract on tissue antioxidant defense system and histological changes of pancreatic beta-cells in streptozotocin-induced diabetic rats

Oxidative stress is produced under diabetic conditions and is likely involved in the progression of pancreatic damage found in diabetes. This study was undertaken to evaluate the protective effect of Aegle marmelos leaf extract, a medicinal plant, on the tissue antioxidant defense system and lipid peroxidative status in streptozotocin-induced diabetic rats. Ethanol extract of A. marmelos was administered orally for 30 days (150 mg/kg body weight/day) to diabetic rats. Activity of the three primary scavenger enzymes (superoxide dismutase, catalase, and glutathione peroxidase), levels of glutathione, and lipid peroxidation were estimated in plasma and pancreas of diabetic rats and compared to the reference drug, glibenclamide (600 microg/kg body weight/day). A significant increase in the levels of plasma glucose, vitamin E, ceruloplasmin, lipid peroxides, and a concomitant decrease in the levels of vitamin C and reduced glutathione were observed in diabetic rats. The activities of antioxidant enzymes were altered in diabetic rats. These alterations were reverted back to near normal levels after treatment with A. marmelos and glibenclamide. Histopathological studies also revealed the protective effect of A. marmelos on pancreatic beta-cells. The present study indicates that extract of A. marmelos modulates the activity of enzymic and nonenzymic antioxidants and enhances the defense against reactive oxygen species-generated damage in diabetic rats.

Effect of Indian herbal hypoglycemic agents on antioxidant capacity and trace elements content in diabetic rats

In the present investigation we report the protective potential of some herbal hypoglycemic agents on antioxidant status and levels of metal ions in streptozotocin-induced diabetic rats. Furthermore, in vitro antioxidant activity of the herbs was also evaluated. Induction of diabetes mellitus in rats caused an increase in blood lipid peroxide levels that was associated with the reduced activity of red blood cell (RBC) antioxidant enzymes--namely, superoxide dismutase, catalase, glutathione reductase, and glutathione peroxidase--along with depletion of plasma reduced glutathione (GSH) and copper, zinc, iron, magnesium, and selenium levels. Oral treatment of diabetic rats with Allium sativum, Azadirachta indica, Momordica charantia, and Ocimum sanctum extracts (500 mg/kg of body weight) not only lowered the blood glucose level but also inhibited the formation of lipid peroxides, reactivated the antioxidant enzymes, and restored levels of GSH and metals in the above-mentioned model. The herbal extracts (50-500 microg) inhibited the generation of superoxide anions (O(2)(-.)) in both enzymatic and nonenzymatic in vitro systems. These preparations also inhibited the ferrous-sodium ascorbate-induced formation of lipid peroxides in RBCs. The in vivo and in vitro protective effects of the above-mentioned herbal drugs were also compared with that of glibenclamide. On the basis of our results, we conclude that the above-mentioned herbal plants not only possess hypoglycemic properties, but they also decrease oxidative load in diabetes mellitus. Therefore, we propose that long-term use of such agents might help in the prevention of diabetes-associated complications. However, the extrapolation of these results to humans needs further in-depth study.

Antidiabetic effect of Phlomis anisodonta: effects on hepatic cells lipid peroxidation and antioxidant enzymes in experimental diabetes

The present study investigated the effects of aerial parts of Phlomis anisodonta methanolic extract (PAE) on streptozotocin (STZ)-induced diabetic rats by measuring fasting blood glucose, serum insulin, change in body weight, ferric reducing antioxidant power (FRAP), lipid peroxidation (LPO), and liver antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx). Male Wistar rats were randomly divided into six groups of six animals. Treatment of diabetic rats with oral administration of PAE at doses of 100, 200 and 400 mg kg(-1) for 10 days resulted in a significant reduction in fasting blood glucose, and an increase in serum insulin levels in comparison with diabetic control group. PAE also protected rats from STZ-induced loss in body weight. Hepatic FRAP increased and LPO in diabetic rats decreased after treatment by PAE at doses of 200 and 400 mg kg(-1). PAE-treated diabetic rats at three doses indicated a significant increase in hepatic SOD, CAT, and GPx activities. These results suggest that PAE is beneficial in the control of diabetes by reduction of blood glucose and increasing insulin levels and combating oxidative stress by activation of hepatic antioxidant enzymes.

Antioxidant and protective effect of latex of Calotropis procera against alloxan-induced diabetes in rats

In the present study, dry latex (DL) of Calotropis procera possessing potent anti-inflammatory activity was evaluated for its antioxidant and anti-hyperglycemic effects against alloxan-induced diabetes in rats. Daily oral administration of DL at 100 and 400 mg/kg doses produced a dose-dependent decrease in the blood glucose and increase in the hepatic glycogen content. DL also prevented the loss of body weight in diabetic rats and brought down the daily water consumption to values comparable to normal rats. DL also produced an increase in the hepatic levels of the endogenous antioxidants, namely superoxide dismutase (SOD), catalase and glutathione, while it brought down the levels of thiobarbituric acid-reactive substances (TBARS) in alloxan-induced diabetic rats. The efficacy of DL as an antioxidant and as an anti-diabetic agent was comparable to the standard anti-diabetic drug, glibenclamide.