Cetirizine and loratadine-based antihistamines with 5-lipoxygenase inhibitory activity

Loratadine and analogues: discovery and preliminary structure-activity relationship of inhibitors of the amino acid transporter B(0)AT2

B(0)AT2, encoded by the SLC6A15 gene, is a transporter for neutral amino acids that has recently been implicated in mood and metabolic disorders. It is predominantly expressed in the brain, but little is otherwise known about its function. To identify inhibitors for this transporter, we screened a library of 3133 different bioactive compounds. Loratadine, a clinically used histamine H1 receptor antagonist, was identified as a selective inhibitor of B(0)AT2 with an IC50 of 4 μM while being less active or inactive against several other members of the SLC6 family. Reversible inhibition of B(0)AT2 was confirmed by electrophysiology. A series of loratadine analogues were synthesized to gain insight into the structure-activity relationships. Our studies provide the first chemical tool for B(0)AT2.

Design, synthesis and biological activity evaluation of desloratadine analogues as H1 receptor antagonists

A series of N-substituted desloratadine analogues were designed and synthesized. They were tested for H1 antihistamine activity by inhibiting histamine-induced contraction of isolated ileum muscles of guinea-pigs in vitro and inhibiting histamine-induced asthmatic reaction in guinea-pigs in vivo. All the evaluated compounds exhibited significant antihistamine activity compared with desloratadine. Five active compounds induced no sedative effects on mouse and four of them exhibited lower anticholinergic side effects than desloratadine. Among these analogues, compound 10, (1S,4S)-4-chlorocyclohexyl desloratadine displayed the highest activity and best safety profile. And it was believed to be a potential candidate as the 3rd generation antihistamine.

Synthesis and antihistamine evaluations of novel loratadine analogues

A series of loratadine analogues containing hydroxyl group and chiral center were synthesized. The effect of the synthesized compounds on the histamine-induced contractions of guinea-pig ileum muscles was studied. In addition, the in vivo asthma-relieving effect of the analogues in the histamine induced asthmatic reaction in guinea-pigs was determined. Most of the compounds exhibited definite H(1) antihistamine activity. The S-enantiomers, compounds 2, 4 and 8, are more potent than the R-enantiomers, compounds 1, 3 and 7. Compound 6 was the most active one among the eight synthesized compounds.

5-Lipoxygenase inhibition by N-hydroxycarbamates in dual-function compounds

A series of N-hydroxycarbamates containing a histaminergic H(1) receptor antagonist pharmacophore was synthesized. In vitro assays determined the compounds had both histaminergic binding and 5-lipoxygenase inhibiting activities comparable to the corresponding N-hydroxyurea analog. Animal models demonstrated antihistaminergic and the 5-lipopxygenase inhibitory activity, with the N-hydroxyurea analog having a better overall profile.