Fractionation Of Volatile Constituents From Traditional Chinese Medicine By Preparative Gas Chromatography

As one of the primary active components of traditional Chinese medicines(TCM), essential oils possessing excellent pharmacological activity are studied more and more deeply. In addition, as one of the important sources of chemical standards, volatile pure compounds are necessary in controlling the quality of TCMs. However, because of some factors(volatile, instability,most are trace and so on)of itself, there are a series of problems to separate and purify pure active compounds of essential oils. It is the key to search an efficient and convenient method in the fractionation of essential oils.Preparative GC is modified on a regular analytical GC for the purpose to obtain pure compounds. Comparing to classical isolation technique, preparative GC is successful to avoid time-consuming fractionation in multiple steps with the risk of the compound being lost, altered or contaminated. In addition, preparative GC succeeds to the special advantages in the purification of volatile compounds. The main content of this paper summarized as follows:First part: A preparative GC was modified on a commercial analytical GC. Principle of modification is: achieving to collect target compounds, improving the load and resolution, balancing the efficiency of yield and resolution. Project: broadening the injection port and column of analytical GC properly, installing split device and trap device behind the column, balancing the performance of every part at last. Result: a preparative GC adapting to separate and purify essential oils of TCMs.Second part: Fractionation of Ezhu essential oil by preparative GC. Ezhu essential oil was obtained by ultrasonic extraction. After many injections of essential oil and collections of fractions, the volatile pure compounds were crystallized for yield weighing. The isolated fractions were analyzed under the same conditions of pGC. The fractions with high purity were determined to confirm their structures. Five pure compounds whose structures were determined and yields were at milligram level were collected.Third part: Fractionation of Xiangfu essential oils which were extracted with two methods by preparative GC. Xiangfu essential oils were obtained by ultrasonic extraction and steam distillation(purchased from market), respectively. The compounds obtained from this two kinds of Xiangfu essential oils were same in the rough. There were advantages and deficiencies in two methods for preparation. The method of preparative GC used in this paper is simple, easy and reliable in the fractionation of essential oils of TCMs. It is a nice method worth popularization.