A novel approach is presented in order to characterize new lead compounds from natural sources. Many natural products are pro-drugs that are metabolized and activated after oral administration. Nevertheless, this aspect is usually overlooked when searching for new therapeutic agents using classical approaches. In this project Salix sp. (willow bark) and Filipendula ulmaria (meadowsweet) were selected as case studies for the characterization of new leads for anti-inflammatory drugs.
Willow bark (Salix sp. such as Salix alba and others) and meadowsweet (Filipendula ulmaria) extracts are widely used since ancient times because of their anti-inflammatory properties. Salicylic acid, the in vivo metabolite of salicylic alcohol derivatives present in the plant extracts, is responsible for part of the pharmacological activity, but there is increasing evidence that other constituents (genuine or formed after in vivo metabolization, such as catechol for Salix extracts) contribute as well. Meadowsweet also contains salicylates and its precursors (methyl salicylate; salicylaldehyde, salicylalcohol and their glycosides), as well as other phenolic constituents. Nevertheless, its chemistry has been studied less extensively than willow bark and its active constituents are not known, although obviously it can be expected that the salicylates will play a role. Anti-inflammatory activity has been documented by in vitro and animal studies. This supports the use of meadowsweet preparations against inflammatory diseases. In view of the phenolic nature or the main constituents, extensive metabolization after oral intake can be expected.
LC-MS (Liquid Chromatography – Mass Spectrometry) and NMR (Nuclear Magnetic Resonance Spectroscopy) platforms will be established for the fast metabolic profiling of plant extracts, prepared using comprehensive extraction methods to cover the full range of constituents. Secondly, a gastro-intestinal dialysis model (GIDM) simulating human GI metabolization, will be applied in order to activate potential pro-drugs. In addition, the dialysate containing the GI metabolites will be treated with microsomal S9 fractions to mimic liver metabolization. The resulting metabolized samples (before and after S9 treatment) will be profiled using the same LC-MS and NMR platforms, and compared with the original profiles. At the same time all extracts and metabolized extracts will be pharmacologically evaluated in a range of in vitro assays related to antimalarial, anti-nephrolithiasis and anti-inflammatory properties. Pharmacological and chromatographic/ phytochemical data will be analyzed in a metabolomics approach using multivariate data analysis in order to identify pharmacologically active constituents or metabolites. Targeted isolation and final pharmacological evaluation in vitro and in vivo will yield new lead compounds against inflammatory diseases.