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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Type of registration
Retrospectively registered

Titles & IDs
Public title
The effect of Increasing Doses of the Flavonoid Quercetin on Blood Vessel Function and Blood Pressure
Scientific title
The Dose Related Effects of Quercetin-3-O-Glucoside on Vascular Function and Blood Pressure in healthy adults
Secondary ID [1] 288069 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
High blood pressure 296931 0
Cardiovascular disease 296932 0
Condition category
Condition code
Cardiovascular 297176 297176 0 0

Study type
Description of intervention(s) / exposure
The study period is approximately 5 weeks and will require 5 separate visits to the School of Medicine and Pharmacology at Royal Perth Hospital. Each visit will take approximately 2 hours. Volunteers deemed suitable following the screening visit, will be randomised into the study. The study is a randomised, controlled, cross-over design. The subjects will receive each treatment once (0mg, 50mg, 100mg, 200mg and 400mg quercetin-3-O-glucoside), in a random order, with a one week washout period in between. The quercetin will be dissolved in warm water and volunteers will be asked to drink the mixture, blinded to the dose they are receiving. The doses given will be monitored by a study staff not blinded to the treatment. They will also make sure the drink has been finished in the allocated time (10 minutes). There are no known or expected side-effects. Each visit will involve measurement of blood vessel function by non-invasive ultrasound, before and 1 hour after receiving the treatment. Blood pressure will be measured prior to, and 1 hour after treatment; 5 supine measurements will be taken. Volunteers will also be required to give a small blood sample (10ml), 1.5 hours after the treatment, for biochemical analysis of plasma nitrate, nitrite and flavonoid metabolites. Nitrate and nitrite concentrations will be measured by gas chromatography-mass spectrometry (GC-MS). The concentration of flavonoid metabolites will be measured by mass-spectrometry methods.
Intervention code [1] 293381 0
Treatment: Other
Comparator / control treatment
2 grams of maltodextrin will be used as the control treatment. Each of the active treatments will also contain 2g maltodextrin.
Control group

Primary outcome [1] 296777 0
Endothelial dysfunction assessed as percentage change in flow-mediated dilatation (FMD) of the brachial artery using ultrasonography
Timepoint [1] 296777 0
60 minutes post intervention
Secondary outcome [1] 319328 0
Change in office blood pressure assessed using a sphygmomanometer
Timepoint [1] 319328 0
60 minutes post intervention
Secondary outcome [2] 319329 0
Plasma nitric oxide status assessed by measuring plasma concentrations of nitrate and nitrite by gas chromatography/mass spectrometry
Timepoint [2] 319329 0
90 minutes post intervention
Secondary outcome [3] 319392 0
Plasma quercetin metabolites assessed using liquid chromatography/mass spectrometry
Timepoint [3] 319392 0
90 minutes

Key inclusion criteria
Healthy volunteers
Living in Perth, Western Australia, and able to visit the reserach centre
Minimum age
20 Years
Maximum age
70 Years
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
Exclusion criteria included current or recent (less than 12 months) smoking; BMI less than 18 or greater than 35 kg/m2; history of cardiovascular or peripheral vascular disease; a systolic BPless than 100 orgreater than 160 mmHg; a diastolic BP less than 50 or greater than 100 mmHg; diagnosed diabetes, and non-diabetic individuals with fasting plasma glucose concentrationsgreater than 6 mmol/L; psychiatric illness or other major illnesses such as cancer; current or recent (within previous 6 months) significant weight loss or gain (greater than 6% of body weight) or actively trying to lose weight; alcohol intake greater than 210g per week for women and greater than 280 g per week for men; and women who are lactating, pregnant or wishing to become pregnant during the study.

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Each treatment was provided in a disposable coffee cup with a lid to conceal any differences in appearance.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Simple randomisation using a randomisation table created by computer software
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s

The people assessing the outcomes
The people analysing the results/data
Intervention assignment
Other design features
Not Applicable
Type of endpoint(s)
Statistical methods / analysis
The primary outcome measure in this study is a measurement of blood vessel function by non-invasive ultrasound (flow-mediated dilation of the brachial artery). Our group has considerable experience with the use of this technique. Using data from several of our previous trials we expect that the standard deviation for the measurement of flow-mediated dilation of the brachial artery will be approximately 2%. A sample of 15 participants (with paired comparisons) will provide greater than 90% power to detect a 2% difference in flow-mediated dilation between control (0 mg quercetin) and 400 mg quercetin (highest dose). That is, if the true difference in the mean response is greater than or equal to 2%, we will be able to reject the null hypothesis that this response difference is zero with probability (power) greater than 0.9. A sample of 15 participants will also provide greater than 85% power to establish a dose-related effect. That is, if the true slope of the line obtained by regressing flow-mediated dilation against quercetin dose is 0.005, we will be able to reject the null hypothesis that this slope equals zero with probability (power) greater than 0.85. The Type I error probability associated with this test of this null hypothesis is 0.05.
The results of the study will be assessed using Analysis of Covariance to look for differences between treatment groups, adjusting for baseline measurments.

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)

Funding & Sponsors
Funding source category [1] 292499 0
Government body
Name [1] 292499 0
National Health and Medical Research Council
Address [1] 292499 0
GPO Box 1421 Canberra ACT 2601
Country [1] 292499 0
Primary sponsor type
University of Western Australia
35 Stirling Highway
Crawley WA 6009
Secondary sponsor category [1] 291208 0
Name [1] 291208 0
Address [1] 291208 0
Country [1] 291208 0

Ethics approval
Ethics application status
Ethics committee name [1] 293968 0
University of Western Australia Human Research Ethics Committee
Ethics committee address [1] 293968 0
35 Stirling Highway
Crawley WA 6009
Ethics committee country [1] 293968 0
Date submitted for ethics approval [1] 293968 0
Approval date [1] 293968 0
Ethics approval number [1] 293968 0

Brief summary
This project aims to determine if there is a dose-related effect of dietary derived quercetin-3-O-glucoside (commonly found in plant-based fruits and vegetables) on blood vessel function in human volunteers. Quercetin glucosides are the main form of quercetin in the human diet. Quercetin is a flavonoid found in foods such as apples and onions. Our previous short term studies using pure quercetin, or apples, show improved blood vessel function. We now wish to determine if there is a dose related response prior to conducting a large intervention trial. The doses of quercetin-3-O-glucoside to be given are 0mg, 50mg, 100mg, 200mg and 400mg. All of these doses are achievable through dietary changes.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 61966 0
Prof Kevin Croft
Address 61966 0
The University of Western Australia School of Medicine and Pharmacology Rear 50 Murray St, Perth WA 6000
Country 61966 0
Phone 61966 0
+61 8 9224 0275
Fax 61966 0
Email 61966 0
Contact person for public queries
Name 61967 0
Miss Nicola Bondonno
Address 61967 0
The University of Western Australia School of Medicine and Pharmacology Rear 50 Murray St, Perth WA 6000
Country 61967 0
Phone 61967 0
+61 8 9224 0342
Fax 61967 0
Email 61967 0
Contact person for scientific queries
Name 61968 0
Miss Nicola Bondonno
Address 61968 0
The University of Western Australia School of Medicine and Pharmacology Rear 50 Murray St, Perth WA 6000
Country 61968 0
Phone 61968 0
+61 8 9224 0342
Fax 61968 0
Email 61968 0

No information has been provided regarding IPD availability
Summary results
Have study results been published in a peer-reviewed journal?
Other publications
Have study results been made publicly available in another format?
Results – basic reporting
Results – plain English summary