New approaches for identifying biologically active components of botanical natural products / 中国药理学与毒理学杂志

ABSTRACT

Countless studies have been devoted to the scientific evaluation of the safety and/or efficacy of botanical natural products. Investigators involved in such studies face a unique set of challenges. Natural products differ from their pharmaceutical counterparts in that they are typically complex mixtures, for which the identities and quantities of components present are not known. To further complicate matters, the composition of these mixtures will vary depending on source material and method of preparation. Investigators conducting clinical trials with complex botanical natural products must choose from a myriad of potential preparations, which may vary greatly in composition. In making such decisions, it is extremely useful to know which components of the mixture are most likely to be responsible for its purported biological activity (the ″active constituents″). The gold standard approach for identifying active constituents of botanical natural products is bioassay-guided fractionation, in which the mixture is subjected to successive rounds of purification and bioassays until an active compound is identified. Bioassay guided fractionation has historically played a critical role in drug discovery, but is, nonetheless, fraught with challenges. The process is biased towards the most abundant and easily isolatable mixture components, which may not be the most biologically active. Furthermore, if multiple compounds contribute either additively, antagonistically, or synergistically to the observed biological activity of the mixture, activity may be lost upon isolation. As a complementary strategy to bioassay-guided fractionation, our research group has developed untargeted metabolomics strategies to aid in the identification of bioactive mixture components. These strategies involve profiling botanical mixtures using ultraperformance chromatography coupled to high resolving power mass spectrometry. The resulting chemical data is then integrated with biological assay data using bioche?mometric data analysis strategies. Several case studies will be presented illustrating how this approach can be applied, including for the identification of compounds from the botanical green (Camellia sinensis) that inhibit drug metabolizing enzymes. Such studies are being conducted as part of the Center for Excellence in Natural Product Drug Interaction Studies (NaPDI), which is supported by a cooperative agreement with the National Center for Complementary and Integrative Health, a component of the National Institutes of Health.