No abstract

Tri-and tetracyclic nitrogen-bridgehead compounds were designed and synthesized to yield micromolar cholinesterase (ChE) inhibitors. Structure−activity relationships identified potent compounds with butyrylcholinesterase selectivity. These compounds were selected as starting points for the design and synthesis of carbamate-based (pseudo)irreversible inhibitors. Compounds with superior inhibitory activity and selectivity were obtained and kinetically characterized also with regard to the velocity of enzyme carbamoylation. Structural elements were identified and introduced that additionally showed neuroprotective properties on a hippocampal neuronal cell line (HT-22) after glutamate-induced intracellular reactive oxygen species generation. We have identified potent and selective pseudoirreversible butyrylcholinesterase inhibitors that release reversible inhibitors with neuroprotective properties after carbamate transfer to the active site of cholinesterases.

A codrug of the anti-Alzheimer drug tacrine and the natural product silibinin was synthesized. The codrug's biological and pharmacological properties were compared to an equimolar mixture of the components. The compound showed potent acetyl- and butyrylcholinesterase inhibition. In a cellular hepatotoxicity model, analyzing the influence on viability and mitochondria of hepatic stellate cells (HSC), the toxicity of the codrug was markedly reduced in comparison to that of tacrine. Using a neuronal cell line (HT-22), a neuroprotective effect against glutamate-induced toxicity could be observed that was absent for the 1:1 mixture of components. In subsequent in vivo experiments in rats, in contrast to the effects seen after tacrine treatment, after administration of the codrug no hepatotoxicity and no induction of the cytochrome P450 system were noticed. In a scopolamine-induced cognitive impairment model using Wistar rats, the codrug was as potent as tacrine in reversing memory dysfunction. The tacrine-silibinin codrug shows high AChE and BChE inhibition, neuroprotective effects, lacks tacrine's hepatotoxicity in vitro and in vivo, and shows the same pro-cognitive effects in vivo as tacrine, being superior to the physical mixture of tacrine and silibinin in all these regards.

Xanthohumol (XN) is a major prenylated chalcone found in hops, which is used to add bitterness and flavor to beer. In this study, we first investigated the effects of XN on hepatocytes and hepatic stellate cells (HSC), the central mediators of liver fibrogenesis. XN inhibited the activation of primary human HSC and induced apoptosis in activated HSC in vitro in a dose dependent manner (0-20 microM). In contrast, XN doses as high as 50 microM did not impair viability of primary human hepatocytes. However, in both cell types XN inhibited activation of the transcription factor NFkappaB and expression of NFkappaB dependent proinflammatory genes. In vivo, feeding of XN reduced hepatic inflammation and expression of profibrogenic genes in a murine model of non-alcoholic steatohepatitis. These data indicate that XN has the potential as functional nutrient for the prevention or treatment of non-alcoholic steatohepatitis or other chronic liver disease.

Butyrylcholinesterase (BChE) is a promising target for the treatment of later stage cognitive decline in Alzheimer's disease. A set of pseudo-irreversible BChE inhibitors with high selectivity over hAChE was synthesized based on carbamates attached to tetrahydroquinazoline scaffolds with the 2-thiophenyl compound 2p as the most potent inhibitor of eqBChE (KC = 14.3 nM) and also of hBChE (KC = 19.7 nM). The inhibitors transfer the carbamate moiety onto the active site under release of the phenolic tetrahydroquinazoline scaffolds that themselves act as neuroprotectants. By combination of kinetic data with molecular docking studies, a plausible binding model was probed describing how the tetrahydroquinazoline scaffold guides the carbamate into a close position to the active site. The model explains the influence of the carrier scaffold onto the affinity of an inhibitor just before carbamate transfer. This strategy can be used to utilize the binding mode of other carbamate-based inhibitors.