| Alzheimer’s disease (AD) is a common and chronic disease in the aged population. The report from international authoritative organizations estimated that the number of dementia patients would increase to115million in2050. However, there is no drug to cure AD at present. Nerve growth factor (NGF), as one of the drug candidates aganist AD, is essential for neuronal developement, survival and function maintenance. Because it is unable to cross blood brain barrier (BBB), its clinical application is limited. Therefore, more attention has been focused on searching for substances from natural products that have NGF mimic activity and are able to cross BBB.More than100crude extracts from traditional Chinese medicine (TCM) were screened by the PC12cell line, which is a bioassay system. Based on the previous results of our group that Gentiana rigescens Franch had NGF mimic activity, its crude extract was partitioned and separated by silica gel, ODS open column, and then purified by HPLC twice to obtain eleven pure active compounds. The structures and strereochemistry were elucidated by spectroscopic methods and chemical derivatization. These compounds are novel alkyl benzoates with new structures, named as gentisides A-K. They all contain a2,3-dihydroxy benzoate acid unit, various alkyl chain lengths (from17to24carbons) and with or without an isopropyl or isobutyl group at the end of alkyl chain. Gentisides A-K induced neurite outgrowth significantly at the concentrations ranging from1to30μM against PC12cells, and formed network-like structures. The percentages of neurite outgrowth were comparable to the best activity of NGF at40ng/mL. Gentisides A-K belong to a new type of neuritogentic compounds, and brief structure-activity relationship (SAR) suggests that alkyl chain length is important for the neuritogentic activity, while the structure diversity at end of alkyl chain is not.G. rigescens Franch is a traditional medicine and frequently used in the herbal prescriptions in China, it is valuable to study the active fractions. The content of a single gentiside is not enough to further study, so gentisides containing activie fractions (n-GS) would be useful for pharmacological study. Scopolamine-induced memory impairment is used as a mature pathological model for AD study. We investigated the effect of n-GS on scopolamine-induced memory impairment. Behaviour was examined in the novel object recognition test and Y-maze test after scopolamine administration. As a result, n-GS significantly prevented scopolamine-induced memory impairment. In addition, the safety of n-GS was investigated. The results of acute toxicity experiment suggested that the median lethal dose (LD50) of n-GS was higher than5g/kg. It is indicated that n-GS is low toxicity and a promising active fraction to treat AD. These results provide a useful data for drug development of n-GS.To study the SAR of gentisides for drug development, more than one hundred of gentiside derivatives were designed and synthesized by our group. Then the biological activities of them were tested on PC12cells. The results indicated that tetradecyl2,3-dihydroxybenzoate (named as ABG-001) exhibited the best neuritogenic activity against PC12cells. Therefore, it was determined as a lead compound. To investigate the underlying mechanism of action, sixteen inhibitors of major proteins related to signaling pathways of neurite outgrowth were applied. The neurite outgrowth induced by ABG-001on PC12cells were significantly blocked by the inhibitors of mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK), phosphoinositide3-kinase (PI3K) and PKC, respectively. However, the inhibitor of NGF receptor TrkA had no significant effect on ABG-001-induced neurite outgrowth. These results indicated that ABG-001targets other proteins to activate the signaling pathways of MAPK/ERK, PI3K and PKC resulted in neurite outgrowth on PC12cells. The investigation of target of ABG-001is in progress. |
PDF Full Text Request