title: Effect of hawthorn standardized extract on flow mediated dilation in prehypertensive and mildly hypertensive adults: a randomized, controlled cross-over trial.
abstract: BACKGROUND
  Hawthorn extract has been used for cardiovascular diseases for centuries. Recent trials have demonstrated its efficacy for the treatment of heart failure, and the results of several small trials suggest it may lower blood pressure. However, there is little published evidence to guide its dosing. The blood pressure lowering effect of hawthorn has been linked to nitric oxide-mediated vasodilation. The aim of this study was to investigate the relationship between hawthorn extract dose and brachial artery flow mediated dilation (FMD), an indirect measure of nitric oxide release.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
  
  
  BACKGROUND
  This trial has been registered with ClinicalTrials.gov, a service of the U.S. National Institutes of Health: NCT01331486.
authors.affiliation: Department of Family Medicine, University of North Carolina, Chapel Hill, USA. gasher@med.unc.edu
authors.forename: Gary N
authors.initials: GN
authors.lastname: Asher
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Viera
authors.forename: Mark A
authors.initials: MA
authors.lastname: Weaver
authors.forename: Rosalie
authors.initials: R
authors.lastname: Dominik
authors.forename: Melissa
authors.initials: M
authors.lastname: Caughey
authors.forename: Alan L
authors.initials: AL
authors.lastname: Hinderliter
mesh_terms: D000328:Adult; D000368:Aged; D044946:Biflavonoids / Q000494:pharmacology* / Q000592:standards; D001775:Blood Circulation / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D001916:Brachial Artery / Q000187:drug effects; D002392:Catechin / Q000494:pharmacology* / Q000592:standards; D027825:Crataegus / Q000737:chemistry*; D018592:Cross-Over Studies; D006801:Humans; D006973:Hypertension / Q000097:blood* / Q000188:drug therapy; D008875:Middle Aged; D009569:Nitric Oxide / Q000097:blood*; D010342:Patient Acceptance of Health Care; D008517:Phytotherapy; D010936:Plant Extracts / Q000494:pharmacology*; D044945:Proanthocyanidins / Q000494:pharmacology* / Q000592:standards; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D044946:Biflavonoids; D010936:Plant Extracts; D044945:Proanthocyanidins; D009569:Nitric Oxide; C017674:procyanidin; D002392:Catechin