Comprehensive chemical analysis of the flower buds of five Lonicera species by ATR-FTIR, HPLC-DAD, and chemometric methods

ABSTRACT

Abstract Lonicera japonica Thunb., Caprifoliaceae, has been employed in traditional Chinese medicine for thousands of years. However, it is frequently confused with closely related species, and thus, a mixture of these species is commonly used. The sources of Lonicera species must be accurately and rapidly determined to ensure the clinical efficacy of herbal medicines. Attenuated total reflectance Fourier transform infrared spectroscopy and high-performance liquid chromatography with a diode array detector, combined with chemometrics methods, were used to comprehensively evaluate the Lonicera quality. The infrared fingerprint results indicated that the spectra of L. japonica and its related species were very similar in the range 4000-1800 cm-1, however a large number of chemical absorption peaks were observed in the region 1800-600 cm-1 with certain differences. The five Lonicera species had high chlorogenic acid (25.85-67.75 µg/mg), 3,5-di-O-caffeoylquinic acid (11.63-62.58 µg/mg), and 4,5-di-O-caffeoylquinic acid (2.64-30.91 µg/mg) contents. The chemical fingerprints of L. hypoglauca Miq. and L. confusa DC were the most similar to that of L. japonica Thunb. The chemical fingerprints of L. fulvotomentosa P.S. Hsu & S.C. Cheng and L. macranthoides Hands.-Mazz. were very different from that of L. japonica. A loading analysis indicated that the differences in the chemical fingerprints of the Lonicera species were mainly due to variations in the contents of the organic acids and flavonoids. Soft independent modeling of class analogy model was successfully developed to classify unknown samples of the five Lonicera species. This comprehensive, unbiased strategy provides adequate, reliable scientific evidence for authenticating herbal sources, therefore offering a powerful, new route for herbal analysis.