Amyloid-ß Aggregation Inhibitory and Neuroprotective Effects of Xanthohumol and its Derivatives for Alzheimer's Diseases.

BACKGROUND: Xanthohumol has been reported to have cytoprotection through activation of Nrf2-ARE signaling pathway and; it has capability of scavenging free radicals, suggesting its potential for the prevention of neurodegeneration. However, the bio-incompatibility and blood-brain barrier impermeability of xanthohumol hindered its in vivo efficacy potential for treating Alzheimer's disease (AD). OBJECTIVE: We designed and prepared a series of xanthohumol derivatives to enhance the desirable physical, biological and pharmacological properties in particular the blood-brain barrier permeability for intervention of AD. METHODS: We designed and synthesized a novel series of 9 xanthohumol derivatives. Their inhibitory effect on amyloid-ß (1-42), Aß1-42, oligomerization and fibrillation as well as neuroprotection against amyloid-ß induced toxicities, were explored. RESULTS: Among the 9 xanthohumol derivatives, some of them exhibited a moderate to high inhibitory effect on Aß1-42 oligomerization and fibrillation. They were biocompatible and neuroprotective to the SH-SY5Y cells by reducing the ROS generation and calcium uploading that were induced by the amyloid- ß. Importantly, two of the derivatives were found to be blood-brain barrier permeable showing promising potential for AD treatment. CONCLUSION: Two derivatives have been identified to be biocompatible, non-toxic, neuroprotective against Aß-induced toxicities and blood-brain barrier permeable highlighting their promising potential as AD drug candidates for future clinical use.

Inhibition of ß-amyloid Aggregation By Albiflorin, Aloeemodin And Neohesperidin And Their Neuroprotective Effect On Primary Hippocampal Cells Against ß-amyloid Induced Toxicity.

Being one of the hallmarks of Alzheimer's disease, ß-amyloid (Aß) aggregates induce complicated neurotoxicity. Evidences show that the underlying mechanism of neurotoxicity involves a glutamate receptor subtype, N-methyl-D-aspartate (NMDA) receptor, an increase in intracellular calcium(II) ion loading as well as an elevation in oxidation stress. In this work, among the 35 chemical components of Chinese herbal medicines (CHMs) being screened for inhibitors of Aß aggregation, four of them, namely albiflorin, aloeemodin, neohesperidin and physcion, were found for the first time to exhibit a potent inhibitory effect on Aß(1-40) and Aß(1-42) aggregation. Their neuroprotective capability on primary hippocampal neuronal cells was also investigated by MTT assay, ROS assay and intracellular calcium(II) ion concentration measurement. It was interesting to find that physcion was rather toxic to neuronal cells while albiflorin, aloeemodin and neohesperidin reduced the toxicity and ROS induced by both monomeric and oligomeric Aß species. In addition, albiflorin was particularly powerful in maintaining the intracellular Ca(2+) concentration.