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Palmatine is a naturally occurring isoquinoline alkaloid that has been reported to display neuroprotective effects against amyloid- β - (A β -) induced neurotoxicity. However, the mechanisms underlying the neuroprotective activities of palmatine remain poorly characterized in vivo . We employed transgenic Caenorhabditis elegans models containing human A β 1-42 to investigate the effects and possible mechanisms of palmatine-mediated neuroprotection. Treatment with palmatine significantly delayed the paralytic process and reduced the elevated reactive oxygen species levels in A β -transgenic C. elegans . In addition, it increased oxidative stress resistance without affecting the lifespan of wild-type C. elegans . Pathway analysis suggested that the differentially expressed genes were related mainly to aging, detoxification, and lipid metabolism. Real-time PCR indicated that resistance-related genes such as sod-3 and shsp were significantly upregulated, while the lipid metabolism-related gene fat-5 was downregulated. Further studies demonstrated that the inhibitory effects of palmatine on A β toxicity were attributable to the free radical-scavenging capacity and that the upregulated expression of resistance-related genes, especially shsp , whose expression was regulated by HSF-1, played crucial roles in protecting cells from A β -induced toxicity. The research showed that there were significantly fewer A β deposits in transgenic CL2006 nematodes treated with palmatine than in control nematodes. In addition, our study found that A β -induced toxicity was accompanied by dysregulation of lipid metabolism, leading to excessive fat accumulation in A β -transgenic CL4176 nematodes. The alleviation of lipid disorder by palmatine should be attributed not only to the reduction in fat synthesis but also to the inhibition of A β aggregation and toxicity, which jointly maintained metabolic homeostasis. This study provides new insights into the in vivo neuroprotective effects of palmatine against A β aggregation and toxicity and provides valuable targets for the prevention and treatment of AD., Competing Interests: The authors have no competing interest., (Copyright © 2021 Weizhang Jia et al.)

Four new coumarins, micromelosides A-D, together with four known coumarins were isolated from the stem bark of Micromelum falcatum. The complete assignments of the 1H and 13C NMR chemical shifts for these new compounds were achieved by means of 1D and 2D NMR techniques, including 1H-1H COSY, HSQC, HMBC and NOE difference., (Copyright 2009 John Wiley & Sons, Ltd.)