Fang Nianbai, Yu Shanggong, Badger Thomas M
Arkansas Children's Nutrition Center, 1120 South Marshall Street, Little Rock, Arkansas 72202, USA.
J Agric Food Chem. 2003 May 21;51(11):3260-7. doi: 10.1021/jf021162c.
Ferulic acid esters of triterpene alcohols and sterols in rice bran oil have been extensively studied and reported to possess important pharmacological actions. Inconsistent results on the numbers and structures of ferulates have been reported, primarily because of the analytical procedures employed. Conventional methods for analysis of phytosterol content in oil are carried out by characterization of trimethylsilylated derivatives (TMS) using GC-EI-MS after saponification of oils or individual compound isolated from oils. This study developed an LC-MS/MS method for the direct analysis of triterpene alcohol and sterol esters in rice bran oil. In addition to verifying the results of previous research, nine new relatively polar triterpene alcohol and sterol esters were characterized by their retention behaviors in LC and ESI-MS data from both negative- and positive-ion mode. This is the first evidence for the presence of hydroxylated ferulate esters and caffeate esters as part of gamma-oryzanol in rice bran. The method enables rapid and direct on-line characterization of triterpene alcohol and sterol esters in oils. LC-MS/MS equipped with reverse-phase LC and ESI-MS should be well-suited for identification and quantification of the polar metabolites of phytosterols in biological fluids after consumption of rice bran oil or other oils.
米糠油中三萜醇和甾醇的阿魏酸酯已得到广泛研究，并据报道具有重要的药理作用。关于阿魏酸酯的数量和结构，报道的结果并不一致，主要是由于所采用的分析方法。常规的油脂中植物甾醇含量分析方法是在油脂或从油脂中分离出的单个化合物皂化后，通过气相色谱-电子轰击质谱法（GC-EI-MS）对三甲基硅烷基化衍生物（TMS）进行表征来实现的。本研究开发了一种液相色谱-串联质谱法（LC-MS/MS），用于直接分析米糠油中的三萜醇和甾醇酯。除了验证先前研究的结果外，还通过它们在液相色谱中的保留行为以及负离子和正离子模式下的电喷雾电离质谱（ESI-MS）数据，对九种新的相对极性较强的三萜醇和甾醇酯进行了表征。这是米糠中存在羟基化阿魏酸酯和咖啡酸酯作为γ-谷维素一部分的首个证据。该方法能够对油脂中的三萜醇和甾醇酯进行快速直接的在线表征。配备反相液相色谱和电喷雾电离质谱的液相色谱-串联质谱法应非常适合在食用米糠油或其他油脂后，对生物体液中植物甾醇的极性代谢物进行鉴定和定量。
