Fastløsningsfordelingskoeffisient

Fastløsningsfordelingskoeffisient, often abbreviated as log P or log Kow, is a dimensionless quantity used in chemistry and pharmacology to describe the lipophilicity of a compound. It is defined as the logarithm of the ratio of the concentration of a solute in a lipid phase (typically octanol) to its concentration in an aqueous phase (typically water) at equilibrium. This ratio, often referred to as the partition coefficient (P), is then expressed on a logarithmic scale to accommodate a wide range of values and to make the distribution of lipophilic and hydrophilic compounds more manageable.

A high log P value indicates that a compound is more soluble in lipids than in water, meaning it is lipophilic or hydrophobic. Conversely, a low log P value suggests that the compound is more soluble in water, making it hydrophilic. The log P value is a crucial parameter in predicting how a substance will behave in biological systems, such as its absorption, distribution, metabolism, and excretion (ADME) properties. For instance, highly lipophilic compounds may readily cross cell membranes, while highly hydrophilic compounds may remain in the aqueous compartments of the body.

The determination of log P can be achieved through experimental methods, such as the shake-flask method, or through computational (in silico) methods that estimate the value based on the compound's chemical structure. Log P is a fundamental concept in drug design, environmental science, and toxicology, aiding in the selection of molecules with desired properties and the assessment of their potential environmental fate and biological impact.