ABSTRACT
Objective: Genetic reationships betwen Swertia mileensis and its relatives have been researched using Fourier transform infrared (FTIR) spectroscopy combined with chemometrics methods in order to provide a theoretical basis for the development and utilization of medicinal plant resources of genus Swertia. Methods: Infrared spectrum information of Swertia mileensis, Swertia cincta, Halenia elliptica, Swertiaion nervosa, Swertia punicea, and Swertia binchuanennsis was collected and used in this study. Original infrared spectra data were pretreated by these methods including automatic baseline correction, automatic smoothing, ordinate normalization, multiplicative scatter correction and second derivative, and analyzed by principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA) and hierarchical cluster analysis (HCA). Results: Absorption area of relationship between Swertia mileensis and its relatives ranged from 900-400 cm-1, 1 310-900 cm-1, 1 500-1 310 cm-1, 1 800-1 500 cm-1, 2 800-3 000 cm-1, and 3 000-3 500 cm-1. Absorption peaks of the second derivative of fingerprint region in 400 to 1 000 cm-1 were distinct, and the absorption peaks as well as peak numbers, intensities and patterns among species were quite different. Analysis of preprocessed IR data showed that PCA analysis of six Swertia species was superior to PLS-DA analysis. The results of HCA analysis showed that Swertia mileensis was closely related to Swertia cincta and Swertia nervosa. Conclusion: FTIR spectroscopy combined with chemometrics method could discriminate different species of genus Swertia and display the closely genetic relationship of Swertia mileensis and its relatives, furthermore, this research would provide a fast and effective method for studying genetic relationship of genus Swertia.