Effets antihypertenseurs de l’extrait aqueux du mélange des parties aériennes de Bidens pilosa (Asteraceae) et de Cymbopogon citratus (Poaceae) chez le rat de souche Wistar

Abstract

High blood pressure (HBP) is currently one of the major risk factors for cardiovascular and renal diseases. The difficulty in the management of this disease is a global health problem. Nowadays, people are turning to alternative medicine for their health problems. Bidens pilosa (B. pilosa) and Cymbopogon citratus (C. citratus) are deux medicinal plants well known for their antihypertensive effects. In the present study, the effects of the aqueous extract of the mixture of B. pilosa and C. citratus were evaluated on hypertension in order to see if the effective dose can be reduced. After verification of the hypotensive effects of the extract on normotensive rats, a mechanism of action test was performed using some pharmacological antagonists (atropine, L- NAME, yohimbine, indomethacin and propranolol). The antihypertensive effects of the aqueous extract of the mixture of B. pilosa and C. citratus were then evaluated in preventive and curative treatment on secondary hypertension model (alcohol+salt: 5 and 2.46 g/kg respectively) and in curative treatment on essential hypertension model (L-NAME; 25 mg/kg). Haemodynamic parameters were recorded by the invasive method. Serum analysis of the lipid profile (total cholesterol, triglyceride, LDL-cholesterol and HDL-cholesterol), some ions (Ca , Mg , K and Na ) and some liver (ALAT, ASAT, albumin and bilirubin) and kidney (creatinine, urea and uric acid) function parameters was performed. Homogenates from some of target organs (liver, kidney, heart and aorta) were used to assess protein levels, catalase and superoxide dismutase (SOD) activity, and concentrations of reduced glutathione (GSH), malondialdehyde (MDA) and nitrites. Histopathological analysis of these organs was performed using haematoxylin-eosin staining. Acute and sub-chronic toxicity of the extract was assessed. The aqueous extract of the mixture of B. pilosa and C. citratus showed a biphasic hypotensive effect, with a more marked effect at a dose of 10 mg/kg. This effect was partially inhibited with atropine (1 mg/kg), yohimbine (0.1 mg/kg) and L-NAME (5 mg/kg). In both models of hypertension, the aqueous extract of the mixture of B. pilosa and C. citratus (100 and 200 mg/kg) and the plant extracts taken separately at a dose of 200 mg/kg prevented (preventive effect) and corrected (curative effect) the increase in haemodynamic parameters in rats. These beneficial effects were associated with an improvement in lipid profile (increase in HDL-cholesterol and decrease in triglycerides, total cholesterol and LDL-cholesterol), oxidative status (increase in GSH, SOD, catalase and reduced MDA), renal function (increased glomerular filtration rate, reduced creatinine, uric acid and urea levels and maintained fluid and electrolyte balance) and hepatic function (reduced ALAT and ASAT activities, bilirubin and albumin levels). These effects helped to protect the organs involved in regulating blood pressure. The aqueous extract of the mixture of B. pilosa and C. citratus had more pronounced effects at the lowest dose (100 mg/kg) on lipid profile, oxidative stress and renal function than plants taken separately. The lethal dose 50 (LD50) of this extract was greater than 5 g/kg. In sub-chronic toxicity, a significant reduction in body weight was observed only in females. The aqueous extract of the mixture of B. pilosa and C. citratus caused a significant decrease in creatinine concentration in males. In conclusion, the aqueous extract of a mixture of B. pilosa and C. citratus proved to be antihypertensive in both an essential (L-NAME) and secondary (alcohol+salt) hypertension model. This extract, especially at the lowest dose (100 mg/kg), had more marked effects than plants taken separately. These effects are due to the vasorelaxant, lipid- lowering, diuretic, antioxidant, hepato-protective and nephro-protective activities of its compounds. This confirms the idea that polytherapy may have better effects than monotherapy.