Effect of hawthorn standardized extract on flow mediated dilation in prehypertensive and mildly hypertensive adults: a randomized, controlled cross-over trial

We used a four-period cross-over design to evaluate brachial artery FMD in response to placebo or hawthorn extract (standardized to 50 mg oligomeric procyanidin per 250 mg extract). Randomly sequenced doses of hawthorn extract (1000 mg, 1500 mg, and 2500 mg) and placebo were assigned to each participant. Doses were taken twice daily for 3 1/2 days followed by FMD and a 4-day washout before proceeding to the next dosing period.Twenty-one prehypertensive or mildly hypertensive adults completed the study. There was no evidence of a dose-response effect for our main outcome (FMD percent) or any of our secondary outcomes (absolute change in brachial artery diameter and blood pressure). Most participants indicated that if given evidence that hawthorn could lower their blood pressure, they would be likely to use it either in conjunction with or instead of lifestyle modification or anti-hypertensive medications.We found no evidence of a dose-response effect of hawthorn extract on FMD. If hawthorn has a blood pressure lowering effect, it is likely to be mediated via an NO-independent mechanism.This trial has been registered with ClinicalTrials.gov, a service of the U.S. National Institutes of Health: NCT01331486.Hawthorn (Crataegus spp.) is a thorny shrub that grows commonly in northern temperate regions around the world. Typically the leaf and flower, berry, or a combination of all three are consumed as a powder, tea, or liquid extract. Its therapeutic use is reported as early as the 1st century BCE, and references to its use in cardiovascular diseases date to the 1600's [1].The chemical constituents considered to be the primary bioactive components of hawthorn are the flavonoids and oligomeric procyanidins (OPCs) [2]. Hawthorn extracts have been shown to enhance release of nitric oxide (NO) from vascular endothelium causing vasodilation, which appears to be associated with the OPC-rich fraction of hawthorn extract [3-5].While traditional indications for use of hawthorn inc