Quality control methods for herbal medicine : a multifaceted approach

Abstract

The past decade has seen an unprecedented growth in the popularity of complementary medicines in Western countries. As the popularity of complementary medicines continues to grow, serious concerns have been raised about their quality and safety. Herbal medicine quality control (QC) and assurance (QA) poses a great challenge, as the large assortment of complex chemicals and the compositional variation found within herbal mixtures makes analysis especially difficult. Here, the two commonly used paradigms for herbal quality assessment; the compound- and pattern-based approaches are examined using model systems. The compound-based paradigm focuses on the quantitative analysis of one or more chemical constituents of an herb or formulation in order to ensure quality and hence product consistency. The complex nature of the 13-herb Endoherb formulation made it an exemplar model for assessing this approach. The methodology used in this study demonstrates how the systematic QC and QA of a complex herbal mixture can be carried out using a logical and systematic method for the selection of the analytes, and then developing a method for their sensitive, specific and accurate analysis. Several methods of analysis including high-performance liquid chromatography (LC) with photodiode array (PDA) and mass spectrometric (MS) detection, as well as gas chromatography (GC) with MS and flame ionisation detection (FID) were employed for the specific analysis of the selected analytes based on factors such as their polarity, volatility and presence of a chromophore. Sample preparation is rapid and simple, utilising sonication as the extraction method. The results show that increasing the organic modifier in the extraction solvent, even for predominantly polar analytes can increase the analyte extraction efficiency. The pattern-based method compares the chromatographic profile of the extract of a new batch with that of a target or reference batch. Combined with new genetic and pharmacological methods of analysis, the pattern-based approach can be an important addition to the characterisation of herbal authenticity and quality, especially in regards to the quality of the raw materials. E. arvense was used as a model to observe the effect of worldwide cultivation on phytochemical profile, genomic profile and pharmacological activity. LC-MS was shown to provide excellent sensitivity, resolution, and reproducibility for the chemical characterisation of the E. arvense extracts. Chromatographic pre-processing of LC-MS profile data using the statistical software 'R' was necessary for subsequent statistical analysis as the instrumental contribution to the profiles made the detection of peaks cumbersome and the statistical inferences inaccurate. The novel use of k-nearest neighbour analysis combined with principal component analysis allowed for an objective classification of sample grouping. Chemical measurement of the antioxidant capacity of the E. arvense extracts provided a basic and preliminary way to establish quality standards of pharmacological equivalence. Importantly, the results indicate that the implied biological effect of the extracts is not reflected in their chemical profile. Finally, DNA barcoding using the loci rbcL and matK was successfully used to authenticate the raw materials.

Date of Award	2012
Original language	English