Separation and determination of alpinetin and cardamonin in Alpinia katsumadai Hayata by flow injection–micellar electrokinetic chromatography
Introduction
Alpinetin and cardamonin are the two major similar components of the seeds of Alpinia katsumadai Hayata. They have long been known to show many pharmacological activities including antiemetic, depriving dampness, and expelling cold. The analytes are important due to its decoction of lower than 1% concentration stimulates, while that higher than 1% inhibits the intestines of guinea-pigs in vitro [1]. So it is necessary to establish a suitable analytical method to evaluate or control the quality of the herbal medicine. However, under acid or alkaline conditions, alpinetin (7-hydroxy-5-methoxyflavanone) and cardamonin (2, 4-dihydroxy-6-methoxychalcone) can transfer each other (see Fig. 1). Hitherto, only high performance liquid chromatography [2] has been reported for the separation and determination of alpinetin and cardamonin. No application of CE has been reported.
MEKC, which was first introduced by Terabe et al. [3], has been widely used to separate nonionic compounds using the electrokinetic phenomena, and it is also applied to improve the separation selectivity of charged analytes [4], [5]. However, the discontinuous sample introduction mode confined the sample throughput and precision. Compared to conventional sample introduction for CE, the combined FI–CE system provides a continuous, reproducible, and readily automated sample introduction means with enhanced sample throughput and improved repeatability [6], [7], [8], [9], [10], [11], [12], [13]. Previous studies have indicated that MEKC is the method of choice for separation of mixtures of small molecules, such as pharmaceutical agents [14], [15], [16]. In this paper, an FI–MEKC method was firstly developed for the separation and detection of alpinetin and cardamonin. The method was simple, rapid, and continuous automated sampling technique, and it was also applied to the analysis of alpinetin and cardamonin in A. katsumadai Hayata with good results.
Section snippets
Chemicals and materials
Alpinetin and cardamonin were obtained from the National Institute for the Control of Pharmaceutical and Biological Products, China. The purity of standard analytes was checked by determined alpinetin and cardamonin by FI–CE, respectively. In this study, we obtained single peak for alpinetin and cardamonin, respectively. The crude drug of A. katsumadai Hayata was purchased from local drug store. Ethanol was purchased from Tianjin Chemical Corporation (Tianjin, China). SDS was purchased from
Selection of electrolyte solution
Since the separation mechanism in MEKC involves partitioning between the mobile phase, any manipulation of the buffer system will have some effect on the distribution coefficient and therefore on the migration of solutes [17]. The mixed buffer of sodium borate and phosphate has been reported [18]. In addition to stable pH, the borate ions can form complexes with phenols, which enhance the selectivity for phenols separation [19]. In this study, the analytes wholly overlapped without sodium
Conclusions
In this paper, we adopted MEKC mode with ethanol as organic modifiers to improve resolution and avoid peak splitting. The coupling of FI system with CE equipment has been successfully used to analyze alpinetin and cardamonin in A. katsumadai Hayata for the first time. The result indicates the FI provides repeatable and reliable sample introduction for CE. The repeatability was 3.0% and 2.5% with peak area evaluation and 0.68% and 0.50% with migration time evaluation for alpinetin and
Acknowledgement
We kindly acknowledge the National Science Foundation of China (No. 20275014) for supporting this work.
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