Tetrazolylpropan-2-ones as inhibitors of fatty acid amide hydrolase: Studies on structure-activity relationships and metabolic stability

Synthesis, activity and metabolic stability of propan-2-one substituted tetrazolylalkanoic acids as dual inhibitors of cytosolic phospholipase A2α and fatty acid amide hydrolase

“…Due to the susceptibility of the ketone function to metabolic reduction by carbonyl reductases 35,36 we have also examined all target structures for metabolic stability in rat liver S9 fraction in presence of NADPH. 23,32 Under the experimental conditions, nearly all compounds were almost completely metabolised to the appropriate alcohols. The formation of hydroxylated products by cytochrome P450 enzymes was detected to a very low extent, if at all (see ESI†).…”

“…34 For the four tetrazolylpropionic acid and -butyric acid derivatives with terminal phenoxy moiety 12, 17, 18 and 19, it was investigated how the potency changes when the acid chain and the residue bearing the ketone function are no longer in 1,3-but in 1,2-position to each other on the tetrazole residue. It was shown that the stronger angulation of the molecules (20)(21)(22)(23) caused by this structural variation significantly reduced a Values are the means of at least two independent determinations, errors are within ± 20%; IC 50 for cPLA 2 α reference inhibitor AR-C70484XX: 0.0065 ± 0.0011 μM (n = 3); 21 IC 50 for FAAH reference inhibitor URB597: 0.060 ± 0.0067 μM (mean ± standard deviation, n = 4). 28 b Determined by reversed-phase HPLC; log P of the references indomethacin and ibuprofen: 2.9 and 3.2, respectively.…”

“…19 Furthermore, we have recently found that inhibitory potency of propan-2-one inhibitors against FAAH in rat liver S9 homogenate increases when enzyme and inhibitor are preincubated before addition of the substrate, which indicates a covalent inhibition mechanism. However, when NADPH is added after preincubation, the inhibition strength is reduced due to a reduction of the ketones to inactive alcohols by carbonyl reductases present in the liver preparation, 23 indicating the reversibility of the covalent inhibition. Due to the susceptibility of the ketone function to metabolic reduction by carbonyl reductases 35,36 we have also examined all target structures for metabolic stability in rat liver S9 fraction in presence of NADPH.…”

“…The extent of metabolism was evaluated by reversed-phase HPLC with UV or MS detection. 23,32 Aqueous solubility. Thermodynamic solubility was determined analogously a previously described procedure.…”

“…In the course of further investigations, we were able to find derivatives of 4 that either selectively or largely selectively inhibit only cPLA 2 α or FAAH like 5 and 6 , 22 or inhibit both enzymes to about the same extent like 7 . 23 An important structural element of these inhibitors is the central ketone group, which is activated by electron-withdrawing substituents. It is assumed that this reactive group can form covalent bonds with the catalytic serine residues in the active centres of cPLA 2 α or FAAH and thus contributes very strongly to the inhibitory effect, provided that the other functionalities of the molecules allow binding to the enzyme.…”