Determination of honokiol and magnolol in Cortex Magnoliae Officinalis by capillary electrophoresis with electrochemical detection

Capillary electrophoresis with electrochemical detection has been employed for the determination of honokiol and magnolol in Cortex Magnoliae Officinalis (i.e. Magnolia Bark) for the first time. Effects of several important factors such as the concentration and the acidity of the running buffer, separation voltage, injection time, and detection potential were investigated to acquire the optimum conditions. The detection electrode was a 300 μm diameter carbon disc electrode at a working potential of +0.90 V (versus saturated calomel electrode (SCE)). The two analytes can be well separated within 6 min in a 40 cm length fused silica capillary at a separation voltage of 18 kV in a 50 mM borate buffer (pH 9.2). The relation between peak current and analyte concentration was linear over about three orders of magnitude with the detection limits (S/N = 3) of 0.38 and 0.51 μM for honokiol and magnolol, respectively. The proposed method has been successfully applied to monitor the two bioactive constituents in the real plant samples with satisfactory assay results.