Synthesis of some novel 8-(4-Alkylpiperazinyl) caffeine derivatives as potent anti-Leishmania agents

Abstract

In this paper, the synthesis, characterization and the leishmanicidal assessments of novel 8-(4-alkylpiperazinyl) caffeine derivatives have been described. These compounds are new caffeine hybrid molecules that are structurally composed of three compartments comprising caffeinyl, piperazinyl and N-alkyl/aryl residues. The synthesis was carried out through the bromination of caffeine via NBS to attain the 8-bromocaffeine (8-BC) followed by the S_NAr-type reaction with the piperazine which afforded the 8‑piperazinyl caffeine (8-PC). Ultimately, the N-alkylation of 8-PC with diverse alkyl halides acquired the products in good to excellent yields (68-96 %). The in vitro evaluation of synthesized compounds on promastigotes of Leishmania major (MHOM/IR/2002/Mash2) has showed that compounds 9d (ie: 8-(4-heptylpiperazin-1-yl)-1,3,7-trimethyl-1H-purine-2,6(3H,7H)-dione), 9e (ie: 1,3,7-trimethyl-8-(4-octylpipera zin-1-yl)-1H-purine-2,6(3H,7H)-dione) and 9f (ie: 8-(4-decylpiperazin-1-yl)-1,3,7-trimethyl-1H-purine-2,6(3H,7H)-dione) with IC₅₀ = 84 μM, IC₅₀ = 94 μM and IC₅₀ = 89 μM displayed remarkable leishmanicidal activity even stronger than metronidazole (MTZ) and miltefosine as the reference drugs. The SAR analysis indicated the leishmanicidal activity of title compounds depended upon the type of substituents on N4 of piperazine. The in silico physicochemical properties, pharmacokinetic profile, and drug likeness predictions were also carried out for the all synthesized compounds and MTZ. The molecular docking study was also conducted to predict the binding mode and the interaction of 9d as the most and 9a as the least active compounds with pteridine reductase 1 (PTR1) enzyme. The docking results determined that 9d exhibited a strong binding affinity to the active site of the enzyme.

Keywords: 8-BC; 8-PC; Caffeine; Docking; In silico; Leishmanicidal.