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Sasaki T.,Toho University | Li W.,Toho University | Zaike S.,Toho University | Asada Y.,Tokyo University of Science | And 4 more authors.
Phytochemistry | Year: 2013

Phytochemical investigation of the leaves of Ribes nigrum resulted in the isolation of fourteen compounds, including four 7,7′-epoxylignans, three tetrahydrofuran-type sesquilignans, and a spirocyclic dilignan. Their structures were elucidated by extensive spectroscopic analyses and by chemical transformations. The isolated compounds were evaluated for their antioxidant activities using superoxide anion scavenging assay and DPPH free radical scavenging assay. Ribesin D and ribesin G showed the most potent superoxide anion scavenging activity with EC50 values of 1.24 and 1.12 μM, respectively, and the structure-activity relationship was discussed. © 2013 Elsevier Ltd. All rights reserved.

Huang C.,Toho University | Li W.,Toho University | Ma F.,Toho University | Ma F.,Heilongjang Institute for Food and Drug Control | And 3 more authors.
Chemical and Pharmaceutical Bulletin | Year: 2012

Chemical investigation on the roots of Tinospora sagittata resulted in the isolation of three novel cis-clerodane diterpenoids, tinospinosides D, E, and tinospin E, together with two known compounds, columbin and columbin glucoside, and their structures were determined by extensive spectroscopic analyses, chemical reactions and computer-assisted calculations. The inhibitory activity of the isolated compounds and their chemical derivatives on nitric oxide production in lipopolysaccharide and interferon-γ activited J774.1 macrophage-like cells was also evaluated. © 2012 The Pharmaceutical Society of Japan.

Bi X.,Toho University | Bi X.,Heilongjang Institute for Food and Drug Control | Li W.,Toho University | Sasaki T.,Toho University | And 5 more authors.
Bioorganic and Medicinal Chemistry Letters | Year: 2011

A 70% EtOH extract from the bark of Syringa reticulata has shown significant antioxidant activity. Chemical study on the extract resulted in the isolation of seventeen compounds (1-17), including a novel oleosidetype secoiridoid glucoside, reticuloside (1), and the structures were elucidated on the basis of extensive spectroscopic analyses. Among the isolated compounds, jaspolyoside (2), oleuropein (4) and 2-(3,4-dihydroxy)-phenylethyl-β-D- glucopyranoside (17), showed the most potent superoxide anion scavenging activity with the EC 50 values of 4.97, 2.57 and 4.97 lM, respectively. The structure-activity relationship indicated that the presence of 2-(3,4-dihydroxyphenyl)-ethoxy group is important for exhibiting the activity. © 2011 Elsevier Ltd. All rights reserved.

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