Recent advances in effect-directed enzyme assays based on thin-layer chromatography
Thin-layer chromatography (TLC) together with its more modern form HPTLC is a rapid and cost effective analytical tool with a long tradition in quality control of medicinal plants, extracts and natural products. Separated compounds are fixed on the solid silica phase to form a compound library. Through direct coupling of visualizable enzyme reactions on the TLC plate, this compound library can also be used for activity screening. Such TLC-based bioautographic enzyme and enzyme inhibition assays complement first stage development activity screening assays. They provide not only phytochemical results by chromatographic separation, but also additional information about the activity of constituents or fractions in multi-compound mixtures, and thus can reveal and distinguish artefacts generated by certain compound classes. This review summarizes recently introduced TLC bioautographic enzyme assays as well as advances in already existing procedures. Bioautographic enzyme and enzyme inhibitory assays offer a rapid, high-throughput method for screening of secondary metabolite profiles for potential enzyme and enzyme inhibitory activities.