RESUMO
Hibiscus sabdariffa Linn. or also known as roselle which is rich in polyphenols, has been demonstrated to cause loweringof blood pressure in animal and clinical settings. However its exact mechanism of action particularly from polyphenoliccompounds is not clearly understood. Therefore, we aimed to determine the effects of H. sabdariffa polyphenol extract(HPE) towards vascular reactivity and its mechanism of action. The HPE was studied on isolated thoracic aortic ringsfrom normal Sprague-Dawley rats, suspended in a 15-ml organ chambers containing Krebs-Henseleit solution. Thechanges in tension were recorded by isometric transducer connected to data acquisition. HPE relaxed the contractioninduced by phenylephrine (PE, 1 μM) in similar pattern for both endothelium-intact and endothelium denuded aorticrings in dose-dependent manner 0.1 ~ 0.9 mg/ml. The pretreatment with atropine (1 μM), a competitive muscarinicantagonist, and propranolol (1 μM), a non-selective beta- blocker did not alter HPE vasorelaxation response. In addition,HPE did not inhibit the contraction induced by extracellular Ca2+ precontracted by PE (1 μM) or KCl (60 mM), in Ca2+-free solution, suggesting that the relaxation effect of HPE was not via inhibition of calcium channels. In conclusion,HPE demonstrated vasorelaxation effects on rat thoracic aorta although the underlying mechanism is still unknown.The vasorelaxation effect could be via angiotensin type 1 receptor inhibition in the vascular smooth muscle cells or theactivation of hyperpolarizing K+ chan
RESUMO
Background & objectives: The role of oxidative stress in the development of diabetes mellitus and its vascular complications are extensively studied. Hyperglycaemia causes oxidative damage by generation of reactive oxygen species and results in the development of complications. The present study was undertaken with the objective of exploring the anti-hyperglycaemic potential of polyphenolic enriched extract of Ichnocarpus frutescens in streptozotocin induced (n-STZ) neonatal diabetic rats (pups) for six weeks and to study oxidative stress and antioxidant status. Methods: Two days old pups were rendered diabetic by single injection of streptozotocin (90 mg/kg body wt, ip). At the end of the treatment period, the level of blood glucose, serum biochemical markers, serum lipid levels and liver malondialdehyde, tissue antioxidant levels were measured. Results: A marked rise was observed in the levels of fasting blood glucose (230.33 mg/dl), lipid profiles, lipid peroxidative products and a significant decrease in tissue antioxidants (superoxide dismuatase, catalase and reduced glutathione) and serum high density lipoprotein cholesterol levels in STZ treated rats. Oral administration of polyphenolic extract (150 and 300 mg/kg body wt, po) decreased fasting blood glucose levels (187.66 and 170.50 mg/dl, respectively) of STZ-treated diabetic rats significantly (P<0.01), when compared with control rats. In addition, the polyphenolic extract showed favourable effect (P<0.01) on the reduced tissues antioxidants level, liver glycogen level, high density lipoprotein level, with significant (P<0.01) reduction of elevated lipid peroxidation products. Histopathological study of the pancreas showed the protective role of polyphenolic extract. Interpretation & conclusions: Our study showed the antioxidant of effect polyphenolic extract of I. frutescens in STZ induced experimental diabetes. The results also suggested that this polyphenolic rich extract could be potentially useful for hyperglycaemia treatment to correct the diabetic state.