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      Enantiomeric Lignans and Neolignans from Phyllanthus glaucus: Enantioseparation and Their Absolute Configurations

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          Abstract

          Eight pairs of enantiomeric neolignans, norlignans, and sesquineolignans ( 1a/1b8a/ 8b), together with five known neolignans ( 9a/9b and 1012), have been isolated from 70% acetone extract of the whole plants of Phyllanthus glaucus Wall. (Euphorbiaceae). The racemic or partial racemic mixtures were successfully separated by chiral HPLC using different types of chiral columns with various mobile phases. Their structures were elucidated on the basis of extensive spectroscopic data. The absolute configurations of 2a/ 2b were determined by computational analysis of their electronic circular dichroism (ECD) spectrum, and the absolute configurations of other isolates were ascertained by comparing their experimental ECD spectra and optical rotation values with those of structure-relevant compounds reported in literatures. Compounds 4a/ 4b featured unique sesquineolignan skeletons with a novel 7-4′-epoxy-8′-8′′/7′-2′′ scaffold, consisting of an aryltetrahydronaphthalene and a dihydrobenzofuran moiety. The planar structures of compounds 2, 3, 7, and 8 were documented previously; however, their absolute configurations were established for the first time in this study. The antioxidant activities of 1a/ 1b8a/ 8b were evaluated using DPPH free radical scavenging assay, and the results demonstrated that compounds 1b and 3b showed potent DPPH radical scavenging activities with IC 50 values of 5.987 ± 1.212 and 9.641 ± 0.865  μg/mL, respectively.

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          Oxidative stress in the pathology and treatment of systemic lupus erythematosus.

          Oxidative stress is increased in systemic lupus erythematosus (SLE), and it contributes to immune system dysregulation, abnormal activation and processing of cell-death signals, autoantibody production and fatal comorbidities. Mitochondrial dysfunction in T cells promotes the release of highly diffusible inflammatory lipid hydroperoxides, which spread oxidative stress to other intracellular organelles and through the bloodstream. Oxidative modification of self antigens triggers autoimmunity, and the degree of such modification of serum proteins shows striking correlation with disease activity and organ damage in SLE. In T cells from patients with SLE and animal models of the disease, glutathione, the main intracellular antioxidant, is depleted and serine/threonine-protein kinase mTOR undergoes redox-dependent activation. In turn, reversal of glutathione depletion by application of its amino acid precursor, N-acetylcysteine, improves disease activity in lupus-prone mice; pilot studies in patients with SLE have yielded positive results that warrant further research. Blocking mTOR activation in T cells could conceivably provide a well-tolerated and inexpensive alternative approach to B-cell blockade and traditional immunosuppressive treatments. Nevertheless, compartmentalized oxidative stress in self-reactive T cells, B cells and phagocytic cells might serve to limit autoimmunity and its inhibition could be detrimental. Antioxidant therapy might also be useful in ameliorating damage caused by other treatments. This Review thus seeks to critically evaluate the complexity of oxidative stress and its relevance to the pathogenesis and treatment of SLE.
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            Assigning stereochemistry to single diastereoisomers by GIAO NMR calculation: the DP4 probability.

            GIAO NMR shift calculation has been applied to the challenging task of reliably assigning stereochemistry with quantifiable confidence when only one set of experimental data are available. We have compared several approaches for assigning a probability to each candidate structure and have tested the ability of these methods to distinguish up to 64 possible diastereoisomers of 117 different molecules, using NMR shifts obtained in rapid and computationally inexpensive single-point calculations on molecular mechanics geometries without time-consuming ab initio geometry optimization. We show that a probability analysis based on the errors in each (13)C or (1)H shift is significantly more successful at making correct assignments with high confidence than are probabilities based on the correlation coefficient and mean absolute error parameters. Our new probability measure, which we have termed DP4, complements the probabilities obtained from our previously developed CP3 parameter, which applies to the case of assigning a pair of diastereoisomers when one has both experimental data sets. We illustrate the application of DP4 to assigning the stereochemistry or structure of 21 natural products that were originally misassigned in the literature or that required extensive synthesis of diastereoisomers to establish their stereochemistry.
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              An update on bioactive plant lignans.

              Lignans are a class of secondary plant metabolites produced by oxidative dimerization of two phenylpropanoid units. Although their molecular backbone consists only of two phenylpropane (C6-C3) units, lignans show an enormous structural diversity. There is a growing interest in lignans and their synthetic derivatives due to applications in cancer chemotherapy and various other pharmacological effects. This review deals with lignans possessing anticancer, antioxidant, antimicrobial, anti-inflammatory and immunosuppressive activities, and comprises the data reported in more than 100 peer-reviewed articles, so as to highlight the recently reported bioactive lignans that could be a first step towards the development of potential new therapeutic agents.
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                Author and article information

                Journal
                Sci Rep
                Sci Rep
                Scientific Reports
                Nature Publishing Group
                2045-2322
                29 April 2016
                2016
                : 6
                : 24809
                Affiliations
                [1 ]Hubei Key Laboratory of Natural Medicinal Chemistry and Resource Evaluation, School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology , Wuhan 430030, Hubei Province, People’s Republic of China
                [2 ]Department of Pharmacy, the Central Hospital of Wuhan , Wuhan 430014, Hubei Province, People’s Republic of China
                [3 ]State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences , Kunming 650204, People’s Republic of China
                [4 ]Tongji Hospital Affiliated to Tongji Medical College, Huazhong University of Science and Technology , Wuhan 430030, People’s Republic of China
                Author notes
                [*]

                These authors contributed equally to this work.

                Article
                srep24809
                10.1038/srep24809
                4850383
                27126373
                3060cee7-538a-463c-9cbe-5e6cecccd016
                Copyright © 2016, Macmillan Publishers Limited

                This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

                History
                : 06 October 2015
                : 05 April 2016
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