title: Effect of the flavonoid fraction of Lithocarpus polystachyus Rehd. on spontaneously hypertensive and normotensive rats.
abstract: BACKGROUND
  Lilhocarpus polystachys Rehd. (Sweet Tea, ST) is a folk herbal medicine that has been traditionally used as a natural remedy for hypertension in China, whose mechanism remains unveiled. Flavonoid fraction is considered as the major active components in ST. This study aimed to provide experimental evidence for the anti-hypertension activity of flavonoid fraction of ST (ST-F) and investigate the underlying mechanism. The effect of ST-F on the blood pressure of normotensive rats was also to be determined.
  
  
  METHODS
  Spontaneously hypertensive rats (SHRs) were treated with ST-F daily for 10 weeks. Blood pressure of SHRs was measured before and biweekly during ST-F treatment. Subsequently, animals were sacrificed either immediately at the end of treatment or 2 weeks after ST-F treatment discontinuance. The activities of plasma rennin (PRA), angiotensin II (Ang-I), endothelin (ET), nitric oxide (NO), superoxide dismutase (SOD) and malondialdehyde (MDA) were measured as well as skin microcirculatory flux. In normotensive rats, blood pressure was determined after six months' treatment of ST-F.
  
  
  RESULTS
  ST-F treatment significantly reduced the blood pressure of SHRs along with decreasing plasma levels of PRA and Ang II. ST-F did not show obvious effects on plasma levels of ET, NO or SOD, but it significantly decreased the plasma level of MDA and improved skin microcirculatory flux. Compared to the anti-hypertensive drug enalapril, ST-F showed a modest effect on lowering blood pressure of SHRs without obvious withdrawal reactions. But long-term intake of ST-F did not change the blood pressure in normotensive rats.
  
  
  CONCLUSIONS
  ST-F had an antihypertensive effect on SHRs. The underlying mechanism could be related to modulation on the rennin-angiotensin-aldosterone system (RAAS) and antioxidation system, as well as regulation of skin microcirculation. Compared to its anti-hypertensive effect on SHRs, ST-F did not cause hypotension in normotensive rats. The results indicated that ST-F could potentially be used as natural drugs or functional foods for preventing hypertension.
authors: School of Chinese Pharmaceutical Science, Guangzhou University of Chinese Medicine, University Town, Guangzhou 510006, China.
authors: Shao-zhen
authors: SZ
authors: Hou
authors: Shi-jie
authors: SJ
authors: Xu
authors: Dong-xu
authors: DX
authors: Jiang
authors: Shu-xian
authors: SX
authors: Chen
authors: Ling-li
authors: LL
authors: Wang
authors: Song
authors: S
authors: Huang
authors: Xiao-ping
authors: XP
authors: Lai
mesh_terms: D000804:Angiotensin II / Q000097:blood; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology / Q000627:therapeutic use*; D001794:Blood Pressure / Q000187:drug effects; D016232:Endothelins / Q000097:blood; D029962:Fagaceae; D005419:Flavonoids / Q000494:pharmacology / Q000627:therapeutic use*; D006973:Hypertension / Q000097:blood / Q000188:drug therapy* / Q000503:physiopathology; D008297:Male; D008315:Malondialdehyde / Q000097:blood; D008833:Microcirculation / Q000187:drug effects; D009569:Nitric Oxide / Q000097:blood; D008517:Phytotherapy; D010936:Plant Extracts / Q000494:pharmacology / Q000627:therapeutic use*; D051381:Rats; D011918:Rats, Inbred SHR; D017207:Rats, Sprague-Dawley; D012083:Renin / Q000097:blood; D012867:Skin / Q000098:blood supply; D013482:Superoxide Dismutase / Q000097:blood
chemical_list: D000959:Antihypertensive Agents; D016232:Endothelins; D005419:Flavonoids; D010936:Plant Extracts; D000804:Angiotensin II; D009569:Nitric Oxide; D008315:Malondialdehyde; D013482:Superoxide Dismutase; D012083:Renin