# Selected Chromatographic Methods for Determining the Biological Activity of Substances
## 7 Summary  
The biomimetic chromatographic systems discussed in this paper are systems that mimic the drug's environment of action. Biomimetic stationary phases are non-polar phases with different hydrocarbon chain lengths, but also stationary phases that mimic biological membranes consisting of a monolayer of phospholipids forming the cell membrane, protein phases with immobilised proteins, and cholesterol phases. Biomimetic systems are not only systems with a stationary phase that mimics that of biological membranes, but also micellar liquid chromatography systems in which the cell membrane environment is mimicked by surfactant micelles (especially BRIJ 35 -BMC), but also by a stationary C-18 phase whose properties are modified by the sorption of surfactant molecules and mimic the cell membranes better than the C-18 phase.  
Chromotography in non-mimetic systems provides much more information about the effect of a drug compared to studies based only on the n-octanol-water partition coefficient. The efficacy of a drug under development can be assessed using chromatographic data from different biomimetic systems early in the drug's development, long before animal studies are conducted. Chromatographic data can be used to screen new compounds being produced as potential drugs. Chromatographic studies can be performed for compounds that do not meet the Lipinski Rule of Five, i.e., peptides, macrolides [171; 172]. The databases already contain a lot of data obtained for different mimetic systems, and based on these data, semi-empirical models have been developed to predict different pharmacokinetic parameters, i.e., the volume of distribution, the degree of binding of the drug to proteins, toxicity, distribution in tissues, and absorption of the drug from different areas of the body.  
The study of compounds by biomimetic chromatography is limited to compounds with molar masses up to 2000.  
The retention data obtained in different biomimetic chromatographic systems can be used for the prediction of different pharmacokinetic parameters. The IAM-HPLC system can be used for the investigation of drug-membrane interactions [173; 174] and for predicting the permeability of substances through different biological membranes, e.g., blood-brain permeation [175; 176; 173]. Based on chromatographic data obtained in different chromatographic systems and theoretical studies, several models for the prediction of different pharmacokinetic parameters have been developed [177; 178; 179; 54; 71; 18; 19].  
Using chromatographic methods, such as chromatography of cell membranes, it is also possible to study the efficacy of substances' interaction with membrane receptors and through bioassays. Both chromatography of cell membranes and bioassays on a chromatographic plate are used for two purposes: to test the biological activity of newly synthesised substances with potential therapeutic properties and to determine which naturally occurring substances (most commonly those in plants) exhibit biological activity. In the latter aspect, the coupling of chromatography with various methods that allow the identification of substances, i.e., mass spectrometry, NMR, and many others, is invaluable. The use of chromatographic methods in the study of biological activity, supported by numerical and statistical methods, can significantly reduce the time and cost of testing and animal studies required for newly synthesised substances and can be used to detect biologically active substances occurring in nature.  
Conceptualization, I.M.; writing--original draft preparation, I.M.; writing--review and editing, I.M. and E.G.; visualization, I.M. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The authors declare no conflicts of interest.