Preparative-layer chromatography normal phase

Isolation of potential anticancer compounds from bioactive extracts involves bioactivity-guided fractionation. The DNA-damaging natural products encountered in our studies were extracted by MEK and/or methanol, and the general methodology which we have employed in our bioassay-directed fractionation of these extracts is schematically presented in Fig. 7. These fractionations involved solvent-solvent partition, Sephadex LH-20 gel filtration, normal phase and reversed-phase (RP) column, preparative thin-layer and high pressure liquid chromatography (HPLC). Silica gel chromatography was employed only if bioactive compounds were found to be stable under these mildly acidic conditions. 

The main difference between the first four methods [normal chamber RPC (N-RPC), microchamber RPC (M-RPC), ultra-microchamber RPC (U-RPC), and column RPC (C-RPC) 1 lies in the size of the vapor space, that is an essential criterion in rotation planar chromatography. The circular mode of development is always used for on-line preparative separations by all of these methods. The sample is applied near the center of the layer, and the mobile phase is forced through the stationary phase from the center to the outside of the round plate/planar column. The separated compounds are eluted from the layer/planar column as a result of the centrifugal force and collected in a fraction collector. 

---