title: Vasorelaxant effects of the extracts and some flavonoids from the buds of Coreopsis tinctoria.
abstract: BACKGROUND
  The buds of Coreopsis tinctoria Nutt (Compositae) are used in the treatment of hypertension in the Uyghur folk medicine in China.
  
  
  OBJECTIVE
  To investigate vasorelaxant properties of extracts and some flavonoids from C. tinctoria (CT) and their underlying mechanisms in isolated rat thoracic aortic rings.
  
  
  METHODS
  Vasorelaxant effects of ethanol extracts of CT (CTA) and its flavonoids as well as water-ethanol eluates from CTA by AB-8 resins (CTAA∼CTAF) were evaluated on rat aortic rings pre-contracted with phenylephrine (PE, 1 µM) or high KCl (60 µM). We evaluated the effect of CTA, CTAD and CTAE on PE-induced contraction in a Ca²⁺-free medium and a dose-effect curve of Ca²⁺ in pre-contracted ring with high KCl.
  
  
  RESULTS
  Endothelial removal did not modify the effect of CTAD and CTAE (3.00 g/L) neither on PE-pre-contracted rings (164.78 ± 21.44 and 191.47 ± 16.75%) nor on KCl-pre-contracted rings (75.68 ± 10.76 and 125.14 ± 17.41%) compared with intact-endothelium rings pre-contracted with high KCl (100.49 ± 17.30 and 110.81 ± 16.33%). CTAD and CTAE (3.00 g/L) down-regulated the dose-effect curve of Ca²⁺ in pre-contraction with high KCl, and inhibited the pre-contraction with PE in a Ca²⁺-free medium (p < 0.05). Seven flavonoids were obtained from CTAD, of which luteolin (5) and quercetin (6) were found to be the most effective relaxation in rings precontracted with PE (EC₅₀: 0.006 and 0.039 g/L, p < 0.05) or high KCl (EC₅₀: 0.023 and 0.045 g/L, p < 0.05).
  
  
  CONCLUSIONS
  These data demonstrated the vasorelaxant effect of CT, and its mechanism is likely due to an inhibitory effect on calcium movements through cell membranes.
authors.affiliation: Xinjiang Key Laboratory of Xinjiang Uygur Medicine, Xinjiang Institute of Materia Medica, Urumqi, China. Sunyuh1117@yahoo.com.cn
authors.forename: Yu-Hua
authors.initials: YH
authors.lastname: Sun
authors.forename: Jun
authors.initials: J
authors.lastname: Zhao
authors.forename: Hong-Tao
authors.initials: HT
authors.lastname: Jin
authors.forename: Yan
authors.initials: Y
authors.lastname: Cao
authors.forename: Ting
authors.initials: T
authors.lastname: Ming
authors.forename: Lan-Lan
authors.initials: LL
authors.lastname: Zhang
authors.forename: Meng-Ying
authors.initials: MY
authors.lastname: Hu
authors.forename: Hasimu
authors.initials: H
authors.lastname: Hamlati
authors.forename: Shi-Bin
authors.initials: SB
authors.lastname: Pang
authors.forename: Xue-Ping
authors.initials: XP
authors.lastname: Ma
mesh_terms: D000818:Animals; D000959:Antihypertensive Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D001013:Aorta, Thoracic / Q000187:drug effects*; D020013:Calcium Signaling / Q000187:drug effects*; D002681:China; D031945:Coreopsis / Q000737:chemistry* / Q000254:growth & development; D004365:Drugs, Chinese Herbal / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000502:physiology; D020834:Ethnopharmacology; D005419:Flavonoids / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D035264:Flowers / Q000737:chemistry / Q000254:growth & development; D066298:In Vitro Techniques; D047311:Luteolin / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D008297:Male; D010656:Phenylephrine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D011794:Quercetin / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D014662:Vasoconstrictor Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*
chemical_list: D000959:Antihypertensive Agents; D004365:Drugs, Chinese Herbal; D005419:Flavonoids; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D010656:Phenylephrine; D011794:Quercetin; D047311:Luteolin