(三)抑制α-糖苷酶活性 α-糖苷酶通过水解α-1,4糖苷键从有关多糖的非还原端切下葡萄糖。人体对淀粉、糊精、蔗糖等碳水化合物的利用吸收依赖于小肠刷状缘上该酶的活性。α-糖苷酶在血糖代谢过程中起到关键的作用。桑叶多糖,是一种有效的α-糖苷酶抑制剂[33]。Lee等[34]研究发现桑叶的甲醇提取物和水提物对四氧嘧啶高血糖小鼠表现出明显的降血糖作用,能阻止从饮食中摄入的淀粉和葡萄糖的高血糖反应。认为其作用机制可能是抑制了α-糖苷酶的催化反应。此外,从桑白皮、桑叶和桑椹中分得一些多羟基生物碱也具有很好的抑制糖苷酶活性,可以降血糖。另外, 从五味子、虎杖和知母中分离出的化学成分,都有抑制α-糖苷酶活性的作用,从而能够降血糖[33]。 综上所述,中药可以通过不同方式如促进葡萄糖利用、保护胰岛β细胞、促进胰岛素稳定分泌和抑制α-糖苷酶活性等来达到防治糖尿病的目的。而且很多中药不是从单一环节,而是从多方面、多靶点综合产生药效的。由此可见,从中药中寻找治疗糖尿病的有效成分是一种防治糖尿病的有效途径,随着各种中药药用机制逐渐清晰,必然引起国内外人们的广泛重视。 References: [1] Hu S W,Guo R L.Utilitarian Diabetologia(实用糖尿病学)[M].Beijingeople’Surgeon Press,1998. [2] Xu S Y,Bian R L,Cheng X.Pharmacological Experiment Methodology(药理实验方法学)[M].Beijingeople’s Medical Publishing House,2001. [3] Wang L P,Yang B,Zhou L. Studies on the Factors Affecting the Diabetic Model Induced by Alloxan in Mice[J].Journal of Guangxi Medical University (广西医科大学学报),2004,21(1):33-35 [4] Huang M,Wang S K,Wang X F, etal. 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