2005 Volume 53 Issue 3 Pages 319-322
A simple and sensitive method has been developed for determining honokiol and magnolol in fresh Magnolia obovata (M. obovata) by micro high-performance liquid chromatography with electrochemical detection (μHPLC-ECD). Chromatography was performed using a Capcell Pak C-18 UG 120 microbore octadecylsilica (ODS) column, methanol–water–phosphoric acid (65 : 35 : 0.5, v/v/v), as a mobile phase and applied potential at +0.8 V vs. Ag/AgCl. Peak heights were found linearly related to the amounts of honokiol and magnolol injected from 0.67 pg to 2.0 ng (r>0.999). The detection limits (S/N=3) were 0.13 pg, respectively. Honokiol and magnolol of 0.27 ng were detected with relative standard deviation (RSD) of 0.73 and 1.17% (n=5), respectively. Honokiol and magnolol in Magnolia Bark of the Japanese Pharmacopoeia were extracted with 70% methanol, diluted with a mobile phase, and injected into the μHPLC-ECD for determination. Recoveries of honokiol and magnolol in Magnolia Bark exceeded 98.7% with RSD, less than 0.93% (n=5). Determination of the distributions of honokiol and magnolol in bark, phloem, wood, leaf blades, and petioles of fresh M. obovata were made using weight samples of 40—238 mg. This method is useful to determine honokiol and magnolol in M. obovata, which is a candidate for crude magnolia bark for traditional Japanese herbal medicines.
