An Investigation Of The Blood Pressure Lowering And Cardioprotective Effects Of The Freeze Dried Extracts Of Aloe Secundiflora

Abstract

Background: Cardiovascular diseases (CVDs) are a leading cause of morbidity and mortality worldwide. Hypertension is the main driver and its interaction with dyslipidaemia and diabetes mellitus accelerates onset and progression of cardiovascular diseases. Herbal products like Aloe secundiflora are used in traditional medicine to improve lifestyle and mitigate these risks. Aim: To investigate the effects of freeze dried extracts of Aloe secundiflora on blood pressure, lipid profile and blood glucose in in-vivo and in-vitro animal models. Setting: Department of Medical Physiology, University of Nairobi. Study design: Experimental animal study. Materials and methods: The chronotropic and inotropic effects of the freeze dried root and leaf extracts of Aloe secundiflora were investigated using the isolated rabbit heart mounted in a Langendorff system of (Power lab TM AD Instruments). Forty (40) Wistar rats were randomly allocated into four groups; the positive control (Atorvastatin 25 mg/Kg), negative control (gavages with distilled water), low dose (40 mg/kg) test and high dose (80 mg/kg) test groups. They were treated and followed up for the five (5) week experimental period. The Blood Pressures were measured at the beginning of the experiment and thereafter at weekly intervals using a VETTM Doppler sphygmomanometer experimental recording system. The blood glucose and lipid profiles were measured at the end of the experimental period. The experimental data were expressed as mean ± Standard Error of Mean and analyzed by one-way ANOVA and Tukey post-hoc tests. The significance level was set at p < 0.05. Results: The freeze dried crude root extract significantly reduced the contractility of the isolated rabbit heart, (p <0.001), but had no chronotropic effect at the test doses. There was no significant difference across the different doses. The freeze dried leaf extract reduced the heart rate and contractility, (p < 0.05), showing significant differences across the test doses. The experimental group on a dose of 80 mg/kg of the freeze dried leaf extract had significantly lower systolic blood pressure than the control group by mean 13.9 ± 4.31 mmHg, p= 0.005. The lipid profile showed significantly lower LDL cholesterol in the experimental groups than both vi the positive and negative control groups, p= 0.006. The 80 mg/kg dose experimental group also had significantly higher HDL cholesterol than the other groups. The test groups had significantly lower fasting blood glucose 7.1 ± 0.21 (c) vs. 7.06 ± 0.31 (c) vs. 6.39 ± 0.19 (t) vs. 6.35 ± 0.18 (t), (p = 0.033). There were no significant differences in weights or electrocardiographic features between the control and test experimental groups. Conclusions: The Aloe secundiflora leaf extract had negative inotropic and chronotropic effects, caused a reduction in blood pressure, fasting blood glucose and improved the lipid profile (reduced the LDL and increased the HDL cholesterol) and should be further evaluated for active components for potential development as treatment or prophylaxis for cardiovascular diseases either as a drug or nutritional supplement. KEY WORDS: Aloe secundiflora, Hypertension, Electrocardiogram, Lipid profile, Blood glucose.