Methotrexate interaction with a lipid membrane model of DPPC

Lipophilicity evaluation by RP-HPLC of two homologous series of methotrexate derivatives

A correlation between the structure and lipophilicity has been carried out within the homologous members of two series of aliphatic bis(amides) and lipoamino acid conjugates of the anticancer drug methotrexate. Basing on their reversed-phase HPLC behaviour, the values of the experimental parameter RQ, obtained by using different mobile phases with increasing concentration of acetonitrile, were considered as a parameter of lipophilicity of the tested compounds. A comparison with their calculated log P was also performed.

Correlation of trimethoprim and brodimoprim physicochemical and lipid membrane interaction properties with their accumulation in human neutrophils

Dipalmitoylphosphatidylcholine vesicles were used as a biological membrane model to investigate the interaction and the permeation properties of trimethoprim and brodimoprim as a function of drug protonation. The drug-membrane interaction was studied by differential scanning calorimetry. Both drugs interacted with the hydrophilic phospholipid head groups when in a protonated form. An experiment on the permeation of the two drugs through dipalmitoylphosphatidylcholine biomembranes showed higher diffusion rate constants when the two drugs were in the uncharged form; lowering of the pH (formation of protonated species) caused a reduction of permeation. Drug uptake by human neutrophil cells was also investigated. Both drugs may accumulate within neutrophils; however, brodimoprim does so to a greater extent. This accumulation is probably due to a pH gradient driving force, which allows the two drugs to move easily from the extracellular medium (pH approximately 7.3) into the internal cell compartments (acid pH). Once protonated, both drugs are less able to permeate and can be trapped by the neutrophils. This investigation showed the importance of the physicochemical properties of brodimoprim and trimethoprim in determining drug accumulation and membrane permeation pathways.