Design, synthesis and biological evaluation of 3-piperazinecarboxylate sarsasapogenin derivatives as potential multifunctional anti-Alzheimer agents.

A series of multifunctional 3-piperazinecarboxylate sarsasapogenin derivatives were designed and synthesized against Alzheimer's disease (AD). The protection against HO-triggered oxidative stress in PC12 cells, and inhibition on LPS-induced NO production in RAW264.7 cell lines in vitro by these derivatives were firstly evaluated. Most of the compounds showed better antioxidant and antiinflammatory activities compared with sarsasapogenin, especially AA34 and AA36. Structure-activity relationships revealed that benzyl group, electron-donating group and intramolecular hydrogen bond might be beneficial to enhancing their neuroprotective activities. Moreover, Aβ42 was the optimum predicted target based on the high 3D molecular similarity between compound AA36 and caprospinol. In the following experiments, AA36 significantly protected PC12 cells from Aβ-induced damage and improved learning and memory impairments in Aβ-injected mice. Thus AA36 is regarded as a potent anti-AD agent and N-substituted piperazinecarboxylate can be served as a promising structural unit for anti-AD drug design.