Phytoequivalence in the global marketplace for botanical products (III): using yeast functional genomics to characterize Equisetum arvense extracts from America, Asia and Europe

Using phytochemical profiling by HPTLC, HPLC-PDA-MS/MS, we previously reported that extracts of E. arvense originating from America, Asia and Europe exhibited qualitative and quantitative differences in flavonoid glycosides and phenyl carboxylic acid content [1]. Extracts are considered equivalent and interchangeable by manufacturers of herbal medicines if certified to have originated from the same species and prepared using similar extraction solvents and procedures. The assumption underlying current industry practice is that phytochemical variability between extracts does not impact on their pharmacological activity. Unfortunately, this assumption cannot be easily tested, as human clinical studies would be prohibitively expensive and take years to complete. Therefore, there is a need for simpler, laboratory-based model systems for the characterization of the pharmacological activity of complex herbal extracts. We explored the use of Saccharomyces cerevisiae, the best-studied eukaryotic organism, for this purpose. Specifically, we investigated the effect of E. arvense extracts on S. cerevisiae gene expression using Affymetrix Yeast 2.0 genechip microarrays. Linear modelling and principal component analysis was used to identify differenzial gene expression elicited by the extracts. Changes were found in expression of genes involved in mRNA translation, drug transport and phospholipids metabolic pathways. Comparison of the observed patterns of gene expression with the phytochemical composition of the extracts revealed that the phytochemical variation was reflected in their effect on yeast gene expression. Together, the data show that functional genomics in S. cerevisiae may be developed as a sensitive bioassay for the quality control of herbal extracts.

References: 1. Lee, S. et al. (2008) Planta Med 74(9): 921–922.