| β-secretase (BACE) is a new target related to the arising and process of Alzheimer's disease (AD). Since 1990, more and more attention has been focused on the research of the BACE inhibitors.Aloe vera L. belongs to the Liliaceae family, which is a well-known Chinese traditional herb that has long been used for the treatment of various diseases. Aristolochia manshuriensis Kom. belongs to the Aristolochiaceae family, is also a traditional drug mainly distributed in northeastern regions of China. In high throughput screening (HTS) of plant crude extracts for BACE inhibitory activity, both Aloe vera L. and Aristolochia manshiiriensis Kom. were found to exhibit potent activity. In the course of our search for new bioactive compounds from medicinal plants, their 95% ethanol extract were studied by bioassay guided fractionations.With P-secretase as the active target, bioassay-guided fractionation of Aloe vera L. resulted in the isolation of 16 compounds. On the basis of various spectroscopic analysis and chemical methods, they were identified as aloveroside A (1), allo-aloeresin D (2), C-2'-decoumaroyl-aloeresin G (3), aloeresin D (4), rebaichromone (5), 8-C-glucosyl-7-O-methyl-(R)-aloesol (6), 8-C-glucosyl-7-O-methylaloediol (7), 8-C-glucosyl-(R)-aloesol (8), aloesin (9), barbaloin A (10), elgnica dimer A (11), elgnica dimer B (12), 1,1',8,8'-tetrahydroxy-3,3'-dimethyl-4,7'-bianthracene-9, 9',10-trione (13), aloe-emodin (14),p-coumaroyl aloerin (15) and aloenin B (16). Among them, 1 is a new chromone C-glycoside with a cis-phenylpropanoid moiety, 2 is a new chromone C-glycoside with a side chain of propenyl, and 3 is a new naphthalene derivative with glucoside, rhamnoside and xyloside.Bioassay-guided fractionation of Aristolochia manshiiriensis Kom. resulted in the isolation of 14 compounds, and they were identified as 6-O-p-coumaroyl-D-glucopyranose (17), 6-O-feruloyl-D-glucopyranose (18), aristolochic acid I (19),...
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