高效液相色谱法测定红曲莫纳可林及桔霉素——如何防治色素的干扰

红曲产品存在的色素对桔霉素和莫纳可林K的高效液相色谱分析有干扰作用 ,并造成色谱柱负担过重。消除色素的副面影响显得尤为重要。采用甲苯 /乙酸乙酯 /甲酸为溶剂萃取固态红曲样品 ,可在萃取较少色素的同时最大程度萃取桔霉素。对于液态发酵的红曲样品 ,采用 2倍于发酵液体积的乙醇萃取桔霉素的方法也优于其他方法。在HPLC分析中 ,用红曲的 3种色素与莫纳可林K(酸型和内酯型 )分别进样或混合后进样 ,发现当流动相中的乙腈浓度较高时 ,内酯型莫纳可林K与黄色素有相当接近的出峰时间。同时 ,紫色素、橙色素与酸型莫纳可林K也有相当接近的出峰时间 ,无法完全分离。如果不预先去除红曲色素 ,也可通过降低流动相中乙腈的比例 ,有效分离色素与莫纳可林K ,以提高分析结果的准确性。

Prevention of Pigment Interference in HPLC Analysis of Monascus Citrinin and Monacolins

Pigments existing in the Monascus products have shown to interfere the HPLC analysis of citrinin and manacolins. It is necessary to remove or separate pigments, and so decrease the side effects of the pigments. Mixed solvent composed of toluene/ethyl acetate/formic acid ( 7/3/1) has proved to extract citrinin from powder Monascus samples most effectively, with less pigments extracted at the same time. In the case of Monascus fermentation broth, the method by adding 2 time volume ethanol to the broth to extract citrinin is superior to other methods. It is clearly demonstrated by our experiments that, lactone form monacolin K has nearly same retention time with ankaflavin, and acid form monacolin K has nearly the same retention time with monascorubramine and monascorubrine, when using the mobile phase composed of acetonitrile and water (its pH is adjusted to 2.5 by H 3PO 4) at the ratio 75:25 (v/v). If the acetonitrile concentration in the mobile phase is reduced to 55 or lower, pigments can be separated from the monacolins to ensure accurate HPLC results. But in this way, the time for HPLC analysis is longer.