Objective: The common and variant peak ratio dual-index sequential analysis method could be used exactly in qualitative evaluation of more than two herb samples

to clarify the similarity level among the samples from different areas

and also provide foundation for authenticity identification and quality evaluation of herbs. Method: With the dual indexes of common peak ratio and variant peak ratio

mean value

smoothness and second differential methods were used for the treatment of UV spectrum data to investigate the stability and repeatability of various wave bands of three different polarity solvent extracts (methenyl trichloride

absolute ethanol and water) of Laggera pterodonta. The common peak ratio and variant peak ratio for the different extracts of L. pterodonta were calculated

and qualitative evaluation was performed for L. pterodonta from different areas. Result: The results showed that methenyl trichloride

absolute ethanol and water had the highest extraction ratios at the extraction time of 30

50 and 40 min respectively

with good stability in 20 h. The different dual-index sequential methods of common peak ratio and variant peak ratio were established in the present study according to the size of common peak ratios. The fingerprint spectral data implicated that the highest common peak ratio was 78.57%

and the lowest common peak ratio was 11.11% among different areas of L. pterodonta.