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Effects of a quercetin-rich onion skin extract on 24 h ambulatory blood pressure and endothelial function in overweight-to-obese patients with (pre-)hypertension: a randomised double-blinded placebo-controlled cross-over trial.

Brüll V, Burak C, Stoffel-Wagner B, Wolffram S, Nickenig G, Müller C, Langguth P, Alteheld B, Fimmers R, Naaf S, Zimmermann BF, Stehle P, Egert S - Br. J. Nutr. (2015)

Bottom Line: In addition, quercetin significantly decreased day-time and night-time systolic BP in hypertensives, but without a significant effect in inter-group comparison.In conclusion, supplementation with 162 mg/d quercetin from onion skin extract lowers ABP in patients with hypertension, suggesting a cardioprotective effect of quercetin.The mechanisms responsible for the BP-lowering effect remain unclear.

View Article: PubMed Central - PubMed

Affiliation: 1Department of Nutrition and Food Sciences,Nutritional Physiology,University of Bonn,53115 Bonn,Germany.

ABSTRACT
The polyphenol quercetin may prevent CVD due to its antihypertensive and vasorelaxant properties. We investigated the effects of quercetin after regular intake on blood pressure (BP) in overweight-to-obese patients with pre-hypertension and stage I hypertension. In addition, the potential mechanisms responsible for the hypothesised effect of quercetin on BP were explored. Subjects (n 70) were randomised to receive 162 mg/d quercetin from onion skin extract powder or placebo in a double-blinded, placebo-controlled cross-over trial with 6-week treatment periods separated by a 6-week washout period. Before and after the intervention, ambulatory blood pressure (ABP) and office BP were measured; urine and blood samples were collected; and endothelial function was measured by EndoPAT technology. In the total group, quercetin did not significantly affect 24 h ABP parameters and office BP. In the subgroup of hypertensives, quercetin decreased 24 h systolic BP by -3·6 mmHg (P=0·022) when compared with placebo (mean treatment difference, -3·9 mmHg; P=0·049). In addition, quercetin significantly decreased day-time and night-time systolic BP in hypertensives, but without a significant effect in inter-group comparison. In the total group and also in the subgroup of hypertensives, vasoactive biomarkers including endothelin-1, soluble endothelial-derived adhesion molecules, asymmetric dimethylarginine, angiotensin-converting enzyme activity, endothelial function, parameters of oxidation, inflammation, lipid and glucose metabolism were not affected by quercetin. In conclusion, supplementation with 162 mg/d quercetin from onion skin extract lowers ABP in patients with hypertension, suggesting a cardioprotective effect of quercetin. The mechanisms responsible for the BP-lowering effect remain unclear.

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Related in: MedlinePlus

Fasting plasma concentrations of quercetin (a) (n 68) and totalflavonols (b) (n 68) before and after the 6-week supplementationwith quercetin (162 mg/d; ■) or placebo (□). Values are means and standarddeviations represented by vertical bars. *** Mean value was significantly differentfrom baseline (P<0·0001; intra-group comparison). † Changeduring quercetin treatment was significantly different from change during placebotreatment (P<0·0001; inter-group comparison). Total plasmaflavonols were calculated as follows: total flavonols (nmol/l)=quercetin(nmol/l)+kaempferol (nmol/l)+isorhamnetin (nmol/l)+tamarixetin (nmol/l). The twogroups did not differ significantly with regard to plasma concentrations ofquercetin and total flavonol at baseline (Wilcoxon signed-rank tests).
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fig2: Fasting plasma concentrations of quercetin (a) (n 68) and totalflavonols (b) (n 68) before and after the 6-week supplementationwith quercetin (162 mg/d; ■) or placebo (□). Values are means and standarddeviations represented by vertical bars. *** Mean value was significantly differentfrom baseline (P<0·0001; intra-group comparison). † Changeduring quercetin treatment was significantly different from change during placebotreatment (P<0·0001; inter-group comparison). Total plasmaflavonols were calculated as follows: total flavonols (nmol/l)=quercetin(nmol/l)+kaempferol (nmol/l)+isorhamnetin (nmol/l)+tamarixetin (nmol/l). The twogroups did not differ significantly with regard to plasma concentrations ofquercetin and total flavonol at baseline (Wilcoxon signed-rank tests).

Mentions: Count of returned capsules indicated an almost full compliance of 98·2 (sd 2·6)% and 98·0 (sd 4·1) % during quercetin and placebo consumption, respectively.Compliance to quercetin supplementation was objectively confirmed by a marked increase inplasma concentrations of quercetin and total flavonols by 1149·6 %(P<0·0001) and 828·6 % (P<0·0001),respectively (Fig. 2(a) and (b)). The increase wasmeasurable in all patients receiving quercetin. In addition, plasma concentrations ofkaempferol, isorhamnetin and tamarixetin significantly increased after quercetin but notafter placebo supplementation (data not shown). There was a high inter-individualvariation in plasma quercetin concentrations already at baseline (range for all studysubjects: 0·2–330·5 nmol/l) and after quercetin supplementation (99·1–1313·1 nmol/l).Fig. 2


Effects of a quercetin-rich onion skin extract on 24 h ambulatory blood pressure and endothelial function in overweight-to-obese patients with (pre-)hypertension: a randomised double-blinded placebo-controlled cross-over trial.

Brüll V, Burak C, Stoffel-Wagner B, Wolffram S, Nickenig G, Müller C, Langguth P, Alteheld B, Fimmers R, Naaf S, Zimmermann BF, Stehle P, Egert S - Br. J. Nutr. (2015)

Fasting plasma concentrations of quercetin (a) (n 68) and totalflavonols (b) (n 68) before and after the 6-week supplementationwith quercetin (162 mg/d; ■) or placebo (□). Values are means and standarddeviations represented by vertical bars. *** Mean value was significantly differentfrom baseline (P<0·0001; intra-group comparison). † Changeduring quercetin treatment was significantly different from change during placebotreatment (P<0·0001; inter-group comparison). Total plasmaflavonols were calculated as follows: total flavonols (nmol/l)=quercetin(nmol/l)+kaempferol (nmol/l)+isorhamnetin (nmol/l)+tamarixetin (nmol/l). The twogroups did not differ significantly with regard to plasma concentrations ofquercetin and total flavonol at baseline (Wilcoxon signed-rank tests).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4594049&req=5

fig2: Fasting plasma concentrations of quercetin (a) (n 68) and totalflavonols (b) (n 68) before and after the 6-week supplementationwith quercetin (162 mg/d; ■) or placebo (□). Values are means and standarddeviations represented by vertical bars. *** Mean value was significantly differentfrom baseline (P<0·0001; intra-group comparison). † Changeduring quercetin treatment was significantly different from change during placebotreatment (P<0·0001; inter-group comparison). Total plasmaflavonols were calculated as follows: total flavonols (nmol/l)=quercetin(nmol/l)+kaempferol (nmol/l)+isorhamnetin (nmol/l)+tamarixetin (nmol/l). The twogroups did not differ significantly with regard to plasma concentrations ofquercetin and total flavonol at baseline (Wilcoxon signed-rank tests).
Mentions: Count of returned capsules indicated an almost full compliance of 98·2 (sd 2·6)% and 98·0 (sd 4·1) % during quercetin and placebo consumption, respectively.Compliance to quercetin supplementation was objectively confirmed by a marked increase inplasma concentrations of quercetin and total flavonols by 1149·6 %(P<0·0001) and 828·6 % (P<0·0001),respectively (Fig. 2(a) and (b)). The increase wasmeasurable in all patients receiving quercetin. In addition, plasma concentrations ofkaempferol, isorhamnetin and tamarixetin significantly increased after quercetin but notafter placebo supplementation (data not shown). There was a high inter-individualvariation in plasma quercetin concentrations already at baseline (range for all studysubjects: 0·2–330·5 nmol/l) and after quercetin supplementation (99·1–1313·1 nmol/l).Fig. 2

Bottom Line: In addition, quercetin significantly decreased day-time and night-time systolic BP in hypertensives, but without a significant effect in inter-group comparison.In conclusion, supplementation with 162 mg/d quercetin from onion skin extract lowers ABP in patients with hypertension, suggesting a cardioprotective effect of quercetin.The mechanisms responsible for the BP-lowering effect remain unclear.

View Article: PubMed Central - PubMed

Affiliation: 1Department of Nutrition and Food Sciences,Nutritional Physiology,University of Bonn,53115 Bonn,Germany.

ABSTRACT
The polyphenol quercetin may prevent CVD due to its antihypertensive and vasorelaxant properties. We investigated the effects of quercetin after regular intake on blood pressure (BP) in overweight-to-obese patients with pre-hypertension and stage I hypertension. In addition, the potential mechanisms responsible for the hypothesised effect of quercetin on BP were explored. Subjects (n 70) were randomised to receive 162 mg/d quercetin from onion skin extract powder or placebo in a double-blinded, placebo-controlled cross-over trial with 6-week treatment periods separated by a 6-week washout period. Before and after the intervention, ambulatory blood pressure (ABP) and office BP were measured; urine and blood samples were collected; and endothelial function was measured by EndoPAT technology. In the total group, quercetin did not significantly affect 24 h ABP parameters and office BP. In the subgroup of hypertensives, quercetin decreased 24 h systolic BP by -3·6 mmHg (P=0·022) when compared with placebo (mean treatment difference, -3·9 mmHg; P=0·049). In addition, quercetin significantly decreased day-time and night-time systolic BP in hypertensives, but without a significant effect in inter-group comparison. In the total group and also in the subgroup of hypertensives, vasoactive biomarkers including endothelin-1, soluble endothelial-derived adhesion molecules, asymmetric dimethylarginine, angiotensin-converting enzyme activity, endothelial function, parameters of oxidation, inflammation, lipid and glucose metabolism were not affected by quercetin. In conclusion, supplementation with 162 mg/d quercetin from onion skin extract lowers ABP in patients with hypertension, suggesting a cardioprotective effect of quercetin. The mechanisms responsible for the BP-lowering effect remain unclear.

Show MeSH
Related in: MedlinePlus