Sylvie Léa Wansi

In vivo antioxidant and vasodilating activities of Gmelina arborea (Verberaceae) leaves hexane extract.

Abstract The present study investigated the effects of Gmelina arborea hexane leaves extract on markers of oxidative stress and its vasorelaxant effects on isolated rat aorta, in order to postulate the possible mechanisms involved in the antihypertensive properties of the plant. To evaluate the antioxidant effects of the extract, rats were randomly divided into four groups of five rats each. With the exception to the group receiving Tween (2.5%), the other groups were treated either with NaCl (900mg/kg/day) alone, NaCl (900mg/kg/day) combined with vitamin C (5mg/kg/day) or Gmelina arborea extract (150mg/kg/day). At the end of eight weeks of treatment, animals were sacrificed and some organs as well as blood samples were collected for biochemical analysis. The in vitro vasodilating effects of the extract (0.5-1.5mg/ml) were evaluated using intact and denuded rat thoracic aortic rings or aorta pre-incubated in L-NAME (2µM), indomethacin (2µM) or glibenclamide (2µM) and contracted with phenylephrine (1µM). The in vivo effects of G. arborea hexane extract prevented both left ventricular and vascular hypertrophy, it also modulated lipid metabolism. Moreover, the extract prevented lipid peroxidation, increased superoxide dismutase and catalase activity as well as NO level. On isolated rat aortic rings, the extract induced concentration-dependent vasorelaxant effects. Extract-induced vasodilation was reduced by mechanical denudation of the endothelium as well as pre-treatment with L-NAME, indomethacin or glibenclamide. These results indicate that Gmelina arborea hexane extract possesses bioactive compounds with antioxidant and vasorelaxant properties.

In vitro anti-hyperglycemic and antioxidant properties of extracts from the stem bark of Ceiba pentandra

Abstract Background: The goal of the study was to determine the antidiabetic mechanisms and the antioxidant effects of aqueous (decoction and maceration) and methanol extracts from the stem bark of Ceiba pentandra. Methods: These extracts were tested in vitro on glucose uptake by skeletal muscles and liver slices and on glucose release by liver slices. The antioxidant activities of C. pentandra extracts were investigated at concentrations ranging from 1 to 300 µg/mL on 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydrogen peroxide (H2O2)-induced hemolysis, H2O2-induced brain lipid peroxidation, hydroxyl (˙OH) radical as well as their reducing power. Results: The decoction similarly to insulin exhibited a significant glucose lowering activity. In a hyperglycemic milieu, it significantly increased glucose uptake by the liver by 56.57% and in the skeletal muscle by 94.19%. In a hypoglycemic milieu, it significantly reduced glucose release by the liver by 33.94%. The decoction, maceration and methanol extracts exhibited a significant radical scavenging activity on DPPH with respective EC50 of 87.84, 54.77 and 6.15 µg/mL versus 2.24 µg/mL observed with ascorbic acid. All the extracts showed a significant antioxidant effect on hydroxyl radical, against lipid peroxidation and H2O2-induced hemolysis. The decoction showed the greatest antihemolytic effect with a maximum inhibition of 77.57% at the concentration of 100 µg/mL. C. pentandra extracts also showed a concentration-dependent reducing power. Conclusions: These results suggest that the antidiabetic effect of C. pentandra is due to its ability to increase glucose uptake and to reduce glucose release by target organs. The antioxidant properties of C. pentandra extracts are additional benefit for their antidiabetic effects.

Comparative Anti-hyperglycemic Effects of the Aqueous Extracts of Combretum molle Twigs in Rats

Aim: To evaluate the antidiabetic properties of the aqueous extracts of C. molle twigs in rats. Methods: For the anti-hyperglycemic tests, the extracts at doses of 125, 250 and 500 mg/kg were administered orally to the normal rats and their glycemia was evaluated each 30 minutes during 4 hours. Type 1 diabetes was induced by the intra-peritoneal injection of alloxane (150 mg/kg) in rats. Type 2 diabetes was induced by the sub-cutaneous injection of the dexamethasone (1 mg/kg). Afterwards, animals were treated at doses 250 and 500 mg/kg of the decoction for 14 days (type 1 diabetes) and 8 days (type 2 diabetes). Body weight, glycemia, lipid parameters and atherogenic index were evaluated. Results: The decoction (250 mg/kg) produced a significant (p < 0.05) decrease in the postprandial glycemia at 90 minutes. However, at 120 minutes, a significant regulation of the blood glucose was observed at the dose of 500 mg/kg of the decoction (p < 0.01), maceration (p < 0.05) and infusion (p < 0.05). In addition, the doses 250 and 500 mg/kg of the decoction of C. molle prevented a significant reduction in body weight, hyperglycemia and dyslipidemia, and a significant increase in atherogenic index, which were observed in the type 1 and 2 diabetic subjects. Conclusion: The decoction was showed the greatest hypoglycemic and anti-hyperglycemic activities, thereby confirming his ethnopharmacological use of this extract in the management of diabetes mellitus.

Endothelium nitric oxide-independent vasorelaxant effects of the aqueous extract from Stephania abyssinica on the isolated rat thoracic aorta

Abstract Background: Stephania abyssinica (Dillon & A. Rich) Walp (Menispermaceae) is a medicinal plant used in the west region of Cameroon to treat arterial hypertension. The present study evaluated the vasorelaxant effects of the aqueous (AESA) and methanol (MESA) extracts from the fresh leaves of S. abyssinica on aorta rings isolated from Wistar rats. Methods: Aorta rings with intact endothelium were contracted with KCl (60 mM) or phenylephrine (10−5 M) and exposed to cumulative concentrations of each extract, ranging from 10 to 1,000 µg/mL. The vasorelaxant effects of AESA were further evaluated in presence of Nω-nitro-L-arginine methyl ester (L-NAME, 10−4 M), tetraethylammonium (TEA, 5 µM), glibenclamide (5 µM), propranolol (5 µM), and the association glibenclamide–propranolol (AGP). In another set of experiments, the effect of AESA was evaluated on calcium-induced contraction in a hyperpotassic milieu. Results: AESA and MESA exhibited a concentration-dependent vasorelaxation on KCl-contracted aortic rings with respective EC50 of 160.10 and 346.50 µg/mL. AESA similarly relaxed aortic rings contracted with phenylephrine (EC50, 176.80 µg/mL). The vasorelaxant activity of AESA was not significantly affected by L-NAME but was markedly reduced by TEA, glibenclamide, propranolol, and AGP. AESA strongly inhibited the Ca2+-induced contraction by 95%. Conclusions: These results support the use of S. abyssinica against arterial hypertension and suggest that the vasorelaxant effect of AESA is not mediated via the endothelium/nitric oxide pathway. AESA relaxant properties might be due to an inhibition of Ca2+ influx and/or the activation of ATP-sensitive K+ channels probably via the stimulation of β-adrenergic receptors.