Cenedella R J
Lipids. 1982 Jun;17(6):443-7. doi: 10.1007/BF02535224.
The ability of digitonin to precipitate lanosterol from prepared mixtures and biological sources was evaluated. Commercially available lanosterol was determined to be composed of about 60% lanosterol and 40% dihydrolanosterol. Both sterols were only partially precipitated by digitonin under all conditions examined. The presence of cholesterol increased the precipitation of lanosterol, but never to completion. About 40% of the lanosterols from saponified sheep's-wool fat was not precipitated by digitonin. Also 14C-labeled lanosterol recovered from rat brain following intracerebral injection of 2-[14C]mevalonate was only 70% precipitated by digitonin. Steric hinderance by the methyl groups at carbon -4 is suggested to explain the poor precipitability of this sterol. In conclusion, lanosterol can not be considered to be a digitonide-precipitable sterol equivalent to cholesterol. Caution should be exercised in situations where digitonin-precipitable sterols are being prepared from sources containing significant concentrations of lanosterol (i.e., mass and/or radiolabel).
评估了洋地黄皂苷从制备的混合物和生物来源中沉淀羊毛甾醇的能力。市售羊毛甾醇被测定为由约60%的羊毛甾醇和40%的二氢羊毛甾醇组成。在所有检测条件下，两种甾醇仅被洋地黄皂苷部分沉淀。胆固醇的存在增加了羊毛甾醇的沉淀，但从未完全沉淀。皂化的羊毛脂中约40%的羊毛甾醇不能被洋地黄皂苷沉淀。同样，在脑内注射2-[¹⁴C]甲羟戊酸后从大鼠脑中回收的¹⁴C标记的羊毛甾醇仅70%能被洋地黄皂苷沉淀。有人认为4位甲基的空间位阻可解释这种甾醇沉淀性差的原因。总之，羊毛甾醇不能被认为是一种与胆固醇等效的可被洋地黄皂苷沉淀的甾醇。在从含有高浓度羊毛甾醇（即质量和/或放射性标记）的来源制备可被洋地黄皂苷沉淀的甾醇时应谨慎行事。
