Infrared Fingerprint Spectra Analysis of Toona sinensis Based on Sequential Dual-indexes and Cluster Analysis Method

The methods of sequential analysis of dual-indexes and cluster analysis were utilized to investigate the infrared fingerprints of Toona sinensis(T1~T13)collected from 13 different areas. Results showed that,the T. sinensis from different areas had the similar characteristic peaks of infrared spectra,and the IR characteristic peaks obviously appear as the main characteristic peaks with the type of proteins,polysaccharides,amino acids and polyphenols,but there were still some differences in the number,shape and intensity of the absorption peaks in the range of fingerprint regions 3400~2800 and 1700~1000 cm^-1. The common peak ratio between the samples from different habitats was 27.78%~84.62%,and the variation peak ratio was 0~160%. The samples T7 and T1,T4 from the closer regions were the relatively similar samples with higher common peak ratio(84.62%)and a very low variant peak ratio(18.18%). T5 and T8,T10,T12 from the farther regions were of significant disparity with common peak ratio less than 31.25% and variant peak ratio larger than 100%. The cluster analysis intuitively divided the samples into four categories. The method was relatively simple,but the effect of cluster analysis was relatively poor. The infrared fingerprint coupled with the methods of sequential analysis of dual-indexes and cluster analysis could serve as an auxiliary way to identify different origins of T. sinensis,and provide a basis for identification of T. sinensis from different areas.