In this study, a rapid and highly efficient method was developed for the separation of eight isoquinoline alkaloids using supercritical fluid chromatography. The separation conditions were carefully optimized including stationary phases, additives, backpressure, and temperature. Compared to high-performance liquid chromatography, the use of supercritical fluid chromatography could provide a 13 times faster separation. Subsequently, the method was validated and applied for the determination of eight alkaloids from different parts of Mahonia bealei (Fort.) Carr. (stem, root, leaf, and seed). The results indicated a good repeatability with relative standard deviations for overall precisions lower than 3.2%. The limit of detection was between 0.4 and 2.3 μg/mL while limit of quantitation ranged from 1.5 to 7.5 μg/mL. Recovery ranged from 95.7 to 102.5% indicating a validity of recovery. The content of total eight alkaloids was the highest in stem (66.0 μg/g) and root (65.1 μg/g) compared to leaf or seed. Moreover, anti-acetylcholinesterase activity for those extracts was evaluated by Ellman's colorimetric assay. As a result, the acetylcholinesterase inhibitory activity of the extracted samples was in the following decreasing order: stem > root > leaf or seed. In conclusion, the results indicated that supercritical fluid chromatography could be a useful tool for quality control of Mahonia bealei (Fort.) Carr. containing alkaloids as active compounds.
Keywords: Mahonia bealei (Fort.) Carr; anti-Alzheimer's activity; supercritical fluid chromatography; traditional Chinese medicine.
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