Antioxidant potential of Coriandrum sativum L. seed extract.

The seeds of C. sativum are used as a traditional drug for the treatment of diabetes. The antioxidant and free-radical-scavenging property of seeds in vitro was studied and also investigated whether the administration of seeds curtails oxidative stress in the kidney of streptozotocin-induced diabetic rats. Incorporation of seed powder in the diet led to marked lowering of blood glucose and a rise in the levels of insulin in diabetic rats. A parallel beneficial effect was observed on oxidant –antioxidant balance in the kidney. Addition of coriander seed powder not only inhibited the process of peroxidative damage but also significantly reactivated the antioxidant enzymes and antioxidant levels in diabetic rats. The total polyphenolic content of the seeds was found to be 12.2 gallic acid equivalents (GAE)/g while total flavanoid content was found to be 12.6 quercetin equivalents/g. The seeds also showed scavenging activity against superoxides and hydroxyl radicals in a concentration -dependent manner. Maximum free radical-scavenging action and free radical reducing power of coriander seed extract was observed at a concentration of 50 g GAE. Islet histology structures showed degeneration of pancreatic islets in diabetic rats which was also reduced in diabetic rats treated with seed powder. These results show that C. sativum seeds not only possess antihyperglycemic properties but antioxidative properties also. Increased dietary intake of coriander seeds decrease the oxidative burden in diabetes mellitus.

Insulin sensitizing actions of fenugreek seed polyphenols, quercetin & metformin in a rat model.

Background & objectives: Plant polyphenols have been known to exert anti-diabetic action and promote insulin action. The present study was carried out to compare the effects of administration of fenugreek seed polyphenolic extract (FPEt), quercetin and metformin (a positive control) in an acquired model of insulin resistance (IR). Methods: Adult male Wistar rats divided into seven groups (n=12). IR was induced in groups (groups 2, 3, 4 and 5) by feeding a high fructose diet (FRU) (60 g/100 g diet) for 60 days. From day 16, FRU rats were administered either FPEt (200 mg/kg bw) (group 3), quercetin (50mg/kg bw) (group 4) or metformin (50 mg/kg bw) (group 5) for the next 45 days. Group 1 served as normal control while groups 6 and 7 served as FPEt and quercetin controls respectively. Oral glucose tolerance test (OGTT) was done on day 59 to assess glucose tolerance. At the end of 60 days, the levels of glucose, insulin, triglycerides (TG) and free fatty acids (FFA) were measured in the blood and the activities of insulin-inducible and suppressible enzymes in cytosolic and mitochondrial fractions of liver and skeletal muscle. The extent of tyrosine phosphorylation of proteins in response to insulin was determined by assaying protein tyrosine kinase (PTK) and protein tyrosine phosphatase (PTP) in liver. Results: Fructose caused increased levels of glucose, insulin, TG and FFA, alterations in insulin sensitivity indices, enzyme activities and reduced glycogen content. Higher PTP activity and lower PTK activity suggest reduced tyrosine phosphorylation status. Administration of FPEt or quercetin improved insulin sensitivity and tyrosine phosphorylation in fructose-fed animals and the effect was comparable with that of metformin. Interpretation & conclusions: Our findings indicated that FPEt and quercetin improved insulin signaling and sensitivity and thereby promoted the cellular actions of insulin in this model.

Evaluation of in vitro antioxidant activity of Indian bay leaf, Cinnamomum tamala (Buch. -Ham.) T. Nees & Eberm using rat brain synaptosomes as model system.

The study investigated the perturbation of oxidant-antioxidant balance in brain synaptosomes of diabetic rats and determined the antioxidant and free radical-scavenging property of the Indian bay leaf. Brain synaptosomes were isolated from control and streptozotocin-induced diabetic animals and oxidative stress parameters were assayed. A methanolic extract of bay leaf (BLE) was tested for the polyphenolic content and antioxidant activity by in vitro assays. A significant increase in the levels of lipids and lipid peroxidation products and a decline in antioxidant potential were observed in diabetic rat brain synaptosomes. The total polyphenolic content of BLE was found to be 6.7 mg gallic acid equivalents (GAE)/100g. BLE displayed scavenging activity against superoxide and hydroxyl radicals in a concentration-dependent manner. Further, BLE showed inhibition of Fe(2+)-ascorbate induced lipid peroxidation in both control and diabetic rat brain synaptosomes. Maximum inhibition of lipid peroxidation, radical scavenging action and reducing power of BLE were observed at a concentration of 220 microg GAE. These effects of BLE in vitro were comparable with that of butylated hydroxyl toluene (BHT), a synthetic antioxidant. It can be concluded that synaptosomes from diabetic rats are susceptible to oxidative damage and the positive effects of bay leaf in vitro, could be attributed to the presence of antioxidant phytochemicals.

Taurine prevents collagen abnormalities in high fructose-fed rats.

BACKGROUND & OBJECTIVE: Accumulation of collagen and changes in its physiochemical properties contribute to the development of secondary complications of diabetes. We undertook this study to see the effects of taurine on the content and characteristics of collagen from tail tendon of rats fed with high fructose diet. METHODS: The rats were divided into four groups of six each: control group (CON), taurine-supplemented control group (CON+TAU), taurine supplemented (FRU+TAU) and not supplemented fructose-fed group (FRU). The physico-chemical properties of collagen isolated from the tail tendon were studied. RESULTS: Fructose administration caused accumulation of collagen in tail tendon. Enhanced glycation and advanced glycation end products (AGE)-linked fluorescence together with alterations in aldehyde content, solubility pattern, susceptibility to denaturing agents and shrinkage temperature were observed in fructose-fed rats. Elevated b component of type I collagen was evidenced from the SDS gel pattern of collagen from the fructose-fed rats. Simultaneous administration of taurine alleviated these changes. INTERPRETATION & CONCLUSION: Taurine administration to fructose-rats had a positive influence on both quantitative and qualitative properties of collagen. The results of the present study suggested a role for the action of taurine in delaying diabetic complications and the possible use of taurine as an adjuvant therapeutic measure in the management of diabetes and its complications.

Lipoic acid restores antioxidant system in tissues of hyperinsulinaemic rats.

BACKGROUND & OBJECTIVES: Feeding rats with high fructose induces insulin resistance, hyperinsulinaemia, elevation of blood glucose level and impaired glucose tolerance. Oxidative stress plays a vital role in pathology associated with insulin resistance. The present study was to investigate the effects of alpha-lipoic acid (LA) on the oxidant-antioxidant balance in liver and kidney of high fructose-fed rats. METHODS: Male Wistar rats (170-180 g) were divided into six groups. The control group received diet containing starch; the fructose group was given a high fructose diet (>60% of total calories); the third and fourth groups were given fructose diet and administered with two different doses of lipoic acid as low dose (35 mg/kg body weight) and high dose (70 mg/kg bw) intraperitoneally using olive oil as vehicle; the fifth group received control diet and was administered with lipoic acid (70 mg/kg bw); the sixth group received the control diet and olive oil. The rats were maintained in their respective dietary regimen for 20 days. Lipid peroxidation indices and antioxidant status in liver and kidney were quantitated. RESULTS: The rats fed fructose showed increased levels of lipid hydroperoxides, thiobarbituric acid reactive substances (TBARS), conjugated dienes, and impaired antioxidant defence potential as evidenced by a decrease in the levels of non-enzymatic and enzymatic antioxidants. Treatment with LA to the fructose-fed rats mitigated these alterations and LA was effective uniformly at both the closes. Increased lipid peroxidation and inadequate antioxidant system are observed in the high dose fructose-fed rats. INTERPRETATION & CONCLUSION: LA administration restored the antioxidant potential and lowered lipid peroxidation. These findings strengthen the utility of LA in the management of insulin resistance and associated pathology.

Response of liver antioxidant system to taurine in rats fed high fructose diet.

Fructose-fed rats were more susceptible to peroxidative damage as measured by thiobarbituric acid reactive species. The concentrations of lipid peroxides, diene conjugates, lipofuscin and hydroperoxides were significantly higher. The levels of enzymic antioxidants such as vitamin C, vitamin E and glutathione and activities of antioxidant enzymes were significantly lower in fructose-fed rats. When these rats received taurine in drinking water, peroxidative damage was minimal in both plasma and liver. Taurine was effective in inducing the antioxidant potential in fructose-fed rats. Increased peroxidative damage in liver is likely to be associated with fructose dependent pathology, which could be reduced by taurine by enhancing the antioxidant potential.

Restoration on tissue antioxidants by fenugreek seeds (Trigonella Foenum Graecum) in alloxan-diabetic rats.

The influence of fenugreek seed powder supplementation in the diet on lipid peroxidation and antioxidant status was studied in normal and alloxan-diabetic rats. The protective effect of the aqueous extract of the seeds on the activity of calcium-dependent adenosinetriphosphatase (Ca2+ ATPase) in liver homogenate in the presence of Fe2+/ascorbate in vitro was also investigated. Normal and diabetic rats were provided with a diet supplemented with fenugreek seed powder for 30 days at a dosage of 2 g/kg body weight. The diabetic rats exhibited enhanced lipid peroxidation and increased susceptibility to oxidative stress associated with depletion of antioxidants in liver, kidney and pancreas. However, treatment with fenugreek seed powder normalised the alterations. In normal rats supplementation resulted in increased antioxidant status with reduction in peroxidation. Ca2+ ATPase activity in liver was protected by the aqueous extract to nearly 80% of the initial activity. The findings suggest that the soluble portion of the seeds could be responsible for the antioxidant property.

Effect of training on lipid peroxidation, thiol status and antioxidant enzymes in tissues of rats.

The effect of training on lipid peroxidation, thiol-status and certain antioxidant enzymes of glutathione system was studied in blood and tissues such as liver and skeletal muscle of rats. Exercise training was given by subjecting the rats to treadmill running. Training for a period of 6 weeks resulted in increased lipid peroxidation (P < 0.001) as indicated by thiobarbituric acid test and conjugated diene measurement in liver and muscle. Thiol levels (total and non-protein) were reduced. However, glutathione level in blood was increased and blood lipid peroxides were unaltered as a result of training compared to sedentary controls. Adaptive increases in three antioxidant enzyme activities were observed. The study indicates that training induces adaptation in the glutathione system.

Increased lipid peroxidation in the erythrocytes of kidney stone formers.

The level of lipid peroxidation was significantly increased in erythrocytes and erythrocyte membrane in patients with stone disease. Increased activities of catalase and acetylcholinesterase in the erythrocyte membrane were observed, while hemolysate displayed no significant change in superoxide dismutase activity. The amount of phospholipids in the RBC membrane of patients was significantly increased. Peroxidation was stimulated by oxalate in vitro and was further enhanced in the presence of ferrous ion. The changes in lipid peroxidation and antioxidant enzymes are suggestive of chemical alteration of the RBC membrane during urolithiasis.