Physicochemical prediction of a brain-blood distribution profile in polycyclic amines

Recent investigation into the pharmacological character of the pentacyclo[5.4.0.0(2,6).0(3,10).0(5,9)]undecyl and related polycyclic amines has revealed interesting facts regarding their possible use as neuroprotective agents. At this stage however, a clear shortcoming in the quest for further development of this novel class of compounds is the lack of concrete data on their ability to cross the blood-brain barrier (BBB). Working towards the aim of predicting BBB permeability, a series of related N-substituted 8-amino-8,11-oxapentacyclo[5.4.0.0(2,6).0(3,10).0(5,9)]undecanes were synthesised. Compounds were characterised by both experimental and calculative methods, followed by biological assessment and statistical manipulation of the results obtained. In doing so, a simple biological model was established for the comparative evaluation of brain-blood distribution properties within the class. A highly sensitive ESI-MS.MS analytical procedure was developed for the detection of these compounds in biological tissues, indicating significant drug concentrations in the brain after intraperitoneal administration to C57Bl/6 mice. Stepwise multiple linear regression analysis of all data yielded two meaningful models (R(2)=0.9996 and R(2)=0.7749) depicting lipophilicity (log P(oct)), solvent accessible molecular volume (SV), molar refractivity (MR) and system energy as the prime determinants of the brain-blood profile for these amines. The inherently high lipophilicity potential within the series is attributed to strong hydrophobic influences dominating hydrogen bonding effects. A possible conformational and energy dependent preference at the site of permeation is also suggested. The proposed estimations allow for the expedient and reliable prediction of brain partitioning behaviour for related polycyclic amines, facilitating the early rejection of unsuitable candidates and enabling research to focus on neuroprotective activity.