Hollow urchin-shaped manganese dioxide microspheres immobilized acetylcholinesterase for rapid screening inhibitors from traditional herbal medicines.

Acetylcholinesterase (AChE) is generally considered to be a valuable therapeutic target for Alzheimer's disease (AD). To rapidly screen novel AChE inhibitors from Traditional Chinese medicines (TCMs), polydopamine (PDA) coated hollow urchin-shaped manganese dioxide microspheres (h-MnO2@PDA) were fabricated in this work. AChE was immobilized onto the surface of h-MnO2@PDA for the first time, and the prepared h-MnO2@PDA immobilized AChE coupled with capillary electrophoresis (CE) was applied to AChE inhibitor screening. The enzyme catalytic activity and kinetic performances of the immobilized AChE were determined by measuring the peak areas of 5-thio-2-nitrobenzoic acid (TNB), which was produced by the reaction of thiocholine (TCh) with 5,5-dithiobis-(2-nitrobenzoic acid) (DTNB). Inhibition kinetics for the immobilized AChE was performed by employing huperzine A as model inhibitor, and its inhibition constant and IC50 were determined. The constructed AChE immobilized h-MnO2@PDA presented outstanding pH, thermal and storage stability. Ultimately, the constructed strategy was applied to screen AChE inhibitors from 7 TCMs and Schisandrae Chinensis Fructus was screened out for its superior AChE inhibitory activity. Therefore, our work not only established a platform for efficiently screening novel AChE inhibitors from TCMs, but also provided inspiration for further exploration of Schisandrae Chinensis Fructus as a potential drug for AD.

Kinetics and inhibition study of tyrosinase by pressure mediated microanalysis.

In the present study, pressure mediated microanalysis (PMMA), a fast, convenient and efficient capillary electrophoresis (CE) method was developed for studying enzyme kinetics of tyrosinase and inhibition kinetics of kojic acid, a model inhibitor of tyrosinase. The enzymatic reaction conditions and CE conditions were optimized in order to obtain high enzyme activity and short analysis time. By PMMA, only the product could be detected at 475 nm, and no voltage was applied to separate the product from the reaction mixture thus greatly simplifying the optimization procedure. The spectrophotometric assay and electrophoretically mediated microanalysis (EMMA) were also performed to validate the developed method. With the present method, the Michaelis-Menten constant (Km) was calculated to be 1.347 mM for tyrosinase. The inhibition constant of kojic acid to free tyrosinase (KI) and kojic acid to tyrosinase/L-DOPA complex (KIS) were calculated to be 36.64 and 74.35 µM, respectively, and the half-maximal inhibitory concentration (IC50) was determined to be 46.64 µM for kojic acid. The developed method is fast and convenient for studying enzyme kinetics, inhibition kinetics and further screening enzyme inhibitors.

Sesquiterpenoids with Various Carbocyclic Skeletons from the Flowers of Chrysanthemum indicum.

A phytochemical investigation of the flowers of Chrysanthemum indicum yielded sesquiterpenoids 1-25 with various carbocyclic skeletons, including 10 new (1-10) and 15 known (11-25) analogues. The structures were elucidated via their physical data, while the absolute configuration of compounds 6, 8, and 10 was assessed via electronic circular dichroism analysis. The evaluation of the effect of sesquiterpenoids on porcine epidemic diarrhea virus (PEDV) replication showed that compounds 1-5, 12, 14, 16, 17, 19, and 21 increased cell viability against cell death in PEDV-injected cells. Compounds 2, 12, and 17 were selected and investigated for their inhibition of proteins required for PEDV replication. Compounds 2 and 17 significantly reduced PEDV nucleocapsid and spike protein synthesis compared with azauridin as a positive control.

Polyphenols Isolated from Xanthoceras sorbifolia Husks and Their Anti-Tumor and Radical-Scavenging Activities.

Xanthoceras sorbifolia Bunge. is used in traditional medicine in North China. To evaluate the anti-tumor and radical-scavenging activities of X. sorbifolia husks polyphenols and determine their structure-activity relationships, 37 polyphenols 1-37 were obtained by bioassay-guided fractionation. Two new compounds 1-2, and compounds 5, 6, 8, 9, 11, 14-17, 21-25, 27-29, 31, 33, 34, 36, and 37 were isolated from the genus Xanthoceras for the first time. Compounds 1-37 did not show strong cytotoxicity against the four tested tumor cell lines (A549, HepG2, MGC-803, and MFC) compared to paclitaxel and under the conditions tested in the anti-tumor assay, but compounds 3, 4, 7, 8, 10, 18-20, 25, 26, 29, 30, 32, and 35 exhibited stronger radical-scavenging activity than ascorbic acid in a 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt assay. This was the first report on the anti-tumor and radical-scavenging activities of the polyphenols isolated from X. sorbifolia husks. Overall, the present study contributed valuable information concerning X. sorbifolia husks use in medicine and pharmacology.

New eudesmane-type sesquiterpenoids from the root bark of Pseudolarix kaempferi.

The phytochemical investigation of the root bark of Pseudolarix kaempferi yielded eight eudesmane-type sesquiterpenoids, including three new ones, 1α-hydroxyl-4(14)-en-ß-dihydroagarafuran (1), 1α, 2α-diacetoxy-8ß-isobutanoyloxy-9α-benzoyl oxy-15-ß-(ß-furancarbonyloxy)-4ß, 6ß-dihydroxy-ß-dihydroagarofuran (7), and 1α-acetoxy-2 α-furancarbonyloxy-8ß-isobutanoyloxy-9α-benzoyloxy-15ß-(ß-acetoxy)-4ß, 6ß-dihydroxy-ß-dihydroagarofuran (8). Herein the new compounds 7 and 8 were reported as a mixture. The molecular structures of the isolated compounds were elucidated on the basis of extensive spectroscopic analysis, including UV, IR, NMR, and MS, and comparison with the literature data.

In vitro anti-inflammatory effects of diterpenoids and sesquiterpenoids from traditional Chinese medicine Siegesbeckia pubescens.

Oxidative stress imposed by reactive oxygen species plays a crucial role in pathophysiology of inflammatory diseases. In the present study, sesquiterpenoids and diterpenoids isolated from Siegesbeckia pubescens, a Chinese traditional medicine used to treat arthritis, were evaluated for inhibition of NO production in activated RAW 264.7 macrophages and FMLP/CB induced O2(·-) generation and elastase release in human neutrophils. In the former assay, sesquiterpenoids were more potent than diterpenoids. The C-4 carbonyl group in the carabrane-type sesquiterpenoid 3 and the C-9 ether linkage in the germacrane sesquiterpene 7 were associated with the enhanced potency. Also, for the active ent-kaurane type diterpenoids, esterification of 17-OH with isobutyric acid and acetylation of 18-OH affected the inhibition of O2(·-) generation and elastase release. This report is the first to describe the inhibitory effects on oxidative stress of secondary metabolites from S. pubescens. Its findings suggest that active terpenoids from the herb could be used as lead anti-inflammatory agents.