Establishment of HPLC-DAD multi-wavelength chromatographic fingerprints of Rehmanniae Radix and its application in processing Rehmanniae Radix Praeparae

Objective To develop the multi-wavelength chromatographic fingerprints for Rehmanniae Radix based on chromatographs of HPLC-DAD and to analyze the applicability by endpoint determination in processing Rehmanniae Radix Praeparae.Methods Samples were extracted by ultrasonic method with methanol.The extract solutions were evaporated to dry and the residue was dissolved with 15% methanol.A Waters Sunfire C18 column(250 mm × 4.6 mm,5 μm) was applied.Acetonitrile-0.02% phosphoric acid in water was used as mobile phase for gradient linear eluting.Maximum peak area was the criterion for choosing from overlapping peaks of the same constituent under different wavelengths.The means of common peaks in the multi-wavelength chromatographic fingerprints of Rehmanniae Radix Praeparae chosen randomly were taken as the reference fingerprint index.The optimal processing time was determined by fingerprint similarity analysis between prepared samples and the reference.Results The result indicated that 18 common peaks were available in multi-wavelength chromatographic fingerprint under 205 and 284 nm.The similarity to reference Rehmanniae Radix Praeparae reached the summit after preparing for 25 h.It could be considered to be the optimum time for preparaing Rehmanniae Radix Praeparae.Conclusion The multi-wavelength chromatographic fingerprint is a facility for revealing constituents variations in detail and for accurate controlling the herbal medicine process.