由美國弗吉尼亞州帕洛阿爾托醫療保健機構統籌的一項動物和細胞培養試驗表明，一種主要用於對抗上呼吸道感染的北美草藥金印草，也可能是一種有效的降膽固醇藥物。研究結果刊登於 Journal of Lipid Research。
姓劉研究員及同事們指出，以往的研究發現金印草和其他草藥都含有一種叫黃連素的生物鹼可以降低血脂。在一個發表於2004年自然醫學雜誌的小型臨床試驗發現，一組包括32例高脂血症患者服用由中國草藥黃連(與金印草非常接近）提取的黃蓮素後，病人的膽固醇和甘油三酯水平平均來說下降了約三分之一。
在新的研究中，劉姓研究員發現金印草除含有黃連素外還含有其他有效成分，對高膽固醇人士更為有益。她從細胞培養和倉鼠實驗上發現，其他有益化合物配合黃連素產生協同效應，能有效平衡血脂。她的研究小組發現其中一種有效化合物為Canadine。
研究表明，Canadine及相關化合物有助促進肝臟低密度脂蛋白受體的產生。這種低密度脂蛋白受體粘附到肝細胞表面後，能有效抓住血液中低密度膽固醇（LDL），有效降低血液中“壞”膽固醇水平。
西藥他汀類藥物也有助降低膽固醇，不過其作用包括阻斷一種促進肝臟製造膽固醇的酶發揮作用，令肝臟天然產生的膽固醇降低，這樣會激活低密度脂蛋白受體和肝細胞從血液中抽取更多的有害血脂，其副作用可能包括肝臟和肌肉損傷。
Popular Herb Goldenseal Lowers Cholesterol in Lab TestsAnimal and cell-culture tests by a team at the VA Palo Alto Health Care System have shown that goldenseal root, a popular North American herb used mainly to fight upper respiratory infections, may also be an effective cholesterol-lowering agent. The findings appeared online in the Journal of Lipid Research.
Previous research by Liu and colleagues found that berberine, an alkaloid found in goldenseal and other herbs, could lower lipids. In a small clinical trial published in 2004 in Nature Medicine, a group of Liu's collaborators in China treated 32 hyperlipidemic patients with berberine isolated from the traditional Chinese herb huang lian, like goldenseal, mainly as an antimicrobial. On average, the patients' cholesterol and triglyceride levels dropped by about a third.
In the new research, conducted solely in Liu's VA lab, goldenseal root proved more powerful than berberine by itself as an agent against high cholesterol. Based on the evidence from her cell-culture and hamster experiments, Liu believes that other compounds in goldenseal, in addition to berberine, work in concert to keep lipids in check. Her team identified one of these compounds as canadine. They are working to purify and characterize two others.
The study showed that the compounds boost the production of a protein known as LDLR (liver low-density lipoprotein receptor). Anchored to the surface of liver cells, LDLR grabs particles of LDL, or "bad," cholesterol from the blood and draws them inside the cell. This lowers cholesterol in the bloodstream.
Statin drugs accomplish the same job, but they do so by blocking an enzyme that enables natural production of cholesterol in the liver. When the liver is low in cholesterol, this activates LDLR and liver cells take in more harmful lipids from the bloodstream. Their side effects could include liver and muscle damage.
