Preparing natural products for lab testing in cell-based assays is far from trivial. In order to test natural compounds in cell culture, the compounds of interest must be able to go into solution in the cell culture medium and remain soluble at physiological salinity and pH. For non-water-soluble compounds, certain solvents may be useful, but many solvents are not applicable to biological assays. Sometimes, an in vitro digest is performed before testing, to mimic some of the process a natural product goes through after being consumed.
A cell viability assay helps determine a safe and optimal working dose range must be established in liquid formulation appropriate for cell work before products may be incorporated into cell culture. It is crucial to ensure that the product is tested at a concentration that is high enough to show an effect, but low enough to avoid problems with culture pH, tonicity, and general cytotoxicity. Interference from high salt concentrations or the formation of precipitates must be assessed and addressed.