# Selected Chromatographic Methods for Determining the Biological Activity of Substances
## 5 Cell Membrane Chromatography (CMC)  
CMC is a biomimetic chromatographic method that was proposed by [PERSON] et al. in the early 1990s and is based on the ability of substances to bind to cell membrane receptors [83; 84]. Membrane receptors are integral proteins of the cell membranes which transfer information into the cell by interacting with substances that cannot penetrate the cell membranes (ligands). About 45% of small molecule drugs act by interacting with membrane receptors. Such studies are mostly conducted in vivo--they are important because they inform us about the interactions that directly produce the therapeutic effect of the drug. Therefore, it was hypothesised that chromatography with stationary phases containing membrane receptors could be used to study such interactions. The interaction of a specific ligand with a receptor leads to an increase in the retention of the substance.  
Membrane cell chromatography is an HPLC method, in which the retention of a substance depends on its affinity to membrane receptors, and this influences its retention. The information obtained from CMC, combined with knowledge of cell biology and receptor pharmacology, enables the evaluation of the interaction of a specific ligand with a specific receptor and the simulation of the drug action process. With the development of molecular biology, methods for the cultivation of cell lines with high expression of certain receptor proteins have been developed, and such lines are now recommended for the preparation of the CMSP phase. In recent years, cell lines with high expression of certain receptor proteins have been cultivated with the help of modern molecular biology tools. Plants have always been factories for biologically active compounds. Their therapeutic effects are observed when plant-derived preparations are used. It is therefore important to identify the active substances in plants and herbal preparations that have a therapeutic effect in certain diseases. In the case of substances whose therapeutic effect is achieved through interactions with membrane receptors, the chromatography of cell membranes can provide answers. In order to identify substances that exhibit activity on the receptors in question in question and therefore exert a corresponding therapeutic effect, a sample of an extract of a particular plant is applied to a CMC column, usually with cell lines with high expression of the receptors in question. Substances that interact with receptors have longer retention times than non-receptors. The coupling of CMC with MS enables the identification of the substance. Due to the interaction of substances with receptors, KD values can be obtained by zone elution frontal analysis and the relative standard method described above [85]. Using cell membrane chromatography in combination with mass spectrometry, a number of substances have been identified that interact with specific membrane receptors from different plant materials. CMC is also a chromatography with EGFR receptor (which is strongly expressed in tumour cells and can be used to determine the interaction of biologically active substances with specific receptors. [PERSON] and others have determined the KD value for nine substances with the receptors \(\alpha\)1A-AR, \(\beta\)1B-AR [81; 86], on the basis of guinea pig myocardium cell membrane/CMC interaction of some drugs with \(\beta\)-AR receptor [87; 88] and M-AChR [89], L-Calcium channels [90], H1R receptor [91], and dopamine receptor [92].  
CMC can also be applied to detect substances that act against a specific receptor in natural mixtures. Chromatography of cell membranes is an excellent tool with which to identify substances that interact with specific membrane receptors [93; 94; 95], as well as substances with specific biological activity: anti-allergic [96], anticancer [97; 98; 99; 100; 101; 102; 103; 104; 105; 106], at anti-cardiovascular disease [107; 108; 109; 110], antineoplastic [104; 111; 112; 113], and allergenic substances [114; 115].