Holistic Evaluation of Quality Consistency of Ixeris sonchifolia (Bunge) Hance Injectables by Quantitative Fingerprinting in Combination with Antioxidant Activity and Chemometric Methods

Abstract

A widely used herbal medicine, Ixeris sonchifolia (Bge.) Hance Injectable (ISHI) was investigated for quality consistency. Characteristic fingerprints of 23 batches of the ISHI samples were generated at five wavelengths and evaluated by the systematic quantitative fingerprint method (SQFM) as well as simultaneous analysis of the content of seven marker compounds. Chemometric methods, i.e., support vector machine (SVM) and principal component analysis (PCA) were performed to assist in fingerprint evaluation of the ISHI samples. Qualitative classification of the ISHI samples by SVM was consistent with PCA, and in agreement with the quantitative evaluation by SQFM. In addition, the antioxidant activities of the ISHI samples were determined by both the off-line and on-line DPPH (2, 2-diphenyl-1-picryldrazyl) radical scavenging assays. A fingerprint-efficacy relationship linking the chemical components and in vitro antioxidant activity was established and validated using the partial least squares (PLS) and orthogonal projection to latent structures (OPLS) models; and the online DPPH assay further revealed those components that had position contribution to the total antioxidant activity. Therefore, the combined use of the chemometric methods, quantitative fingerprint evaluation by SQFM, and multiple marker compound analysis in conjunction with the assay of antioxidant activity provides a powerful and holistic approach to evaluate quality consistency of herbal medicines and their preparations.

Fig 1. The chemical structures of seven marker compounds.

Fig 2. The chromatograms and UV absorption spectra of ISHI and standards:

(a) The chromatograms of 23 batches of ISHI samples at 260 nm. (b), (c) The chromatograms of ISHI and mixed standards, respectively. (d), (e) The UV absorption spectra of standards and ISHI, respectively.

Fig 3. PCA score plot (given by SIMCA 13.0) of 23 batches of ISHI samples.

Fig 4. The Y observed versus Y predicted plots and coefficients plots for ISHIs:

(a) Y observed versus Y predicted plot and (b) coefficients plot for PLS model. (c) Y observed versus Y predicted plot and (d) coefficients plot for OPLS model. The bars indicate 95% confidence intervals based on jack-knifing.

Fig 5. HPLC chromatograms of sample S5:

detected at 260 nm (a) and 517nm (b, negative peaks indicating antioxidant activity). The identified peaks include: 4-UR, 10-AD, 24-CGA, 26-CFA, 34-CCA, 38-LGR and 40-LG.