Objective    To establish and optimize a method to extract and determine rhynchophylline in a traditional Chinese herb

Ramulus Uncariae cum Uncis.     Methods    Cold maceration with methanol and supersonic extraction was used to treat the medical material. Chromatography was performed on a Diamonsil C18 column (250 mm×4.6 mm

5  μm). Gradient elution was employed with a mobile phase consisting of methanol (solution A) and ammonium acetate buffer (0.01 mol/L

pH 6.0 adjusted by ammoniae aqua

solution B) as follows: A∶B from 25∶75 to 50∶50 from 0 to 20 min. The flow rate of the mobile phase was 1.0 ml/min and the column was maintained at 20 ℃. The detector was monitored at 245 nm.     Results    The calibr

ation curve was linear among the concentration range of 0.25 to 64.0 μg/ml (y=3.64×10

4

x-2.13×10

4

r=0.999 5) and the relative recovery ranged from 95.95% to 114.4%. The relative standard deviation (RSD) of the reproducibility test was 6.50% and of the stability test was 4.62%

2.65% and 4.58% from the high density to the low.     Conclusion    Our method is accurate

reliable and with good reproducibility

and it can be used for determining rhynchophylline in Ramulus Uncariae cum Uncis.