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Title: Impact of Hibiscus sabdariffa calyces on cardiovascular disease risk markers in human volunteers
Author: Abubakar, Salisu Maiwada
ISNI:       0000 0004 7655 494X
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2016
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Background: Chronic consumption of anthocyanins-rich Hibiscus sabdariffa calyces (HSC) extract has been shown to reduce blood pressure (BP) and improved lipid profile, and inflammatory and oxidative stress markers in humans. However, the impact of HSC extract on postprandial vascular endothelial function, a novel holistic cardiovascular disease (CVD) risk marker, and other cardiometabolic risk factors have not been studied previously. Aim: To investigate the acute impact of HSC extract consumption on BP, vascular function and other cardiometabolic risk markers in men with 1 to 10 % CVD risk. Design: HSC from different countries were analysed for polyphenols using high performance liquid chromatography (HPLC). In vitro antioxidant capacity of HSC samples was performed to choose the most appropriate HSC sample use in human intervention study. This was followed by a randomised, controlled, single - blinded, cross over study involving 25 men (mean age of 49 years and BMI 26.9 kg/m2). Volunteers were randomised to consume either 250 ml of the aqueous extract of HSC containing 150 mg anthocyanins or water with breakfast, followed by a lunch at 2 hours on two separate occasions separated by 2 weeks. BP was measured at baseline and hourly for 4 hours. Further ambulatory BP measurements were taken hourly overnight. Vascular function was measured as flow mediated dilatation (FMD) of the branchial artery and arterial stiffness as augmentation index (Alx) measured by pulse wave analysis (PWA) at baseline, 2 and 4 hours post intervention drink consumption. Blood and urine samples were collected and postprandial responses of glucose, lipids, C- reactive protein (CRP), insulin, nitric oxide, systemic antioxidant potential and HSC anthocyanin and phenolic acid bioavailability were determined. Results: There was a tendency for the HSC drink to attenuate the increase in BP observed with the placebo water drink but this did not reach statistical significance. A significant increase in postprandial % FMD (PcO.OOl) was observed after consumption of HSC extract compared with water. There was no overall change in the systemic antioxidant status, serum glucose, plasma insulin, serum triacylglycerol (TAG), CRP, plasma NOx and arterial stiffness (p > 0.05) following the acute consumption of HSC extract. However, there was a significant (p = 0.026) increase in the area under systemic antioxidant status response curve covering 0 to 2 hours following the acute consumption of the extract of HSC compared with water. Gallic acid, 4-O-methylgallic acid (4OMGA), 3-O-methylgallic acid (3OMGA) and hippuric acid were detected and reached a maximum plasma concentration at Ito 2 hours following acute consumption of the HSC extract but did not show an association with FMD following a stepwise regression analysis. Conclusion: Acute consumption of HSC extract improved postprandial endothelial function, measured by FMD, and increased plasma gallic acid and anthocyanidin metabolites concentrations but did not affect the postprandial response of BP and cardiometabolic risk markers. HSC may be a useful dietary strategy to reduce endothelial dysfunction but this requires more studies to confirm.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available