Characterization of Biologically Active Rhus Typhina Extract Using a Bioassay-Linked- Metabolomics Method

Plants produce natural products to interact with the environment and some of these plant metabolites have biological activity beyond their intrinsic role. Bioactive compounds have the potential to be made into useful products including drugs against resistant pathogens, “organic” agricultural pesticides, and preservatives for pharmaceutical, food, and cosmetic products. Critical in the process of developing a biologically active plant extract into a useful product is the identification and quantification of extract bioactive constituents. Using a bioassay-linked-metabolomics method may provide a way to probe un-fractionated plant extracts to get this information. Additionally, it is important to assess differences in bioactivity level among extracts made from plants collected from distinct geographic locations. To test this method several collections of leaf and berry tissue from the Minnesota native plant Rhus typhina, which displays antimicrobial and antioxidant activity, were collected throughout the state of Minnesota. Separate 70% ethanol extractions were made and evaluated for antimicrobial activity against four representative microorganisms that cause disease and spoilage: gram+ Staphyloccocus aureus, gram- Escherichia coli, the filamentous fungi Fusariam solani, and the yeast Candida albicans using both disc-diffusion and turbidity growth assays. Assays to evaluate extract constituent redox potential were used to assess antioxidant activity. Un-fractionated extracts were then analyzed by reversed-phase liquid chromatography-electrospray ionization- mass spectrometry to obtain metabolic fingerprints. These were analyzed using supervised multivariate statistical techniques to identify the principle components driving differences in bioactivity among extracts. Structural elucidation of these identified features will provide lead compounds for specific bioactivity tests and product development. Using a bioassay-linked-metabolomics method it is possible to efficiently compare extracts made from different populations of plants and to detect specific bioactive constituents from un-fractionated plant extracts.