Determination of oregonin in Alnus plants and biological samples by capillary electrophoresis

Oregonin, existing primarily in the Alnus plants, displayed anti-inflammatory and antioxidative activities. The capillary zone electrophoresis (CZE) method was developed in this study to quantitatively determine oregonin content in the Alnus plants for the first time. Various parameters, including buffer concentration, pH and applied voltage, were evaluated for their optimum analytical conditions. The optimized buffer was composed of 30 mM sodium tetraborate at pH 8.0. The separation voltage was set at 30 kV and the UV detection wavelength was set at 220 nm. Oregonin could be determined within 6 min under such optimized conditions. Relative standard deviation (R.S.D.) of the run-to-run repeatability and intermediate precision of the retention time of oregonin was within 1.36%. Run-to-run repeatability and intermediate precision of the peak area ratios of oregonin to internal standard, theophylline, were both within 1.55% R.S.D. The presented method was applied to analyze oregonin in leaves of Alnus formosana, seeds of various Alnus plants as well as biological samples. The stability of oregonin in biological system was indicated in this study. It demonstrates the potential of this developed method in natural product research.