Hosup Yeo

Cynandione A from Cynanchum wilfordii protects cultured cortical neurons from toxicity induced by H2O2, L‐glutamate, and kainate

Oxidative stress has been implicated as a primary cause of neuronal death in certain neurodegenerative disorders and in aging brains. Natural products have been used in Asian societies for centuries for treating such neurodegenerative disorders as senile dementia. In an effort to identify active neuroprotective compounds from these products, we have employed cultures of rat cortical neurons as our screening system. A methanolic extract from dried roots of Cynanchum wilfordii Hemsley (Asclepiadaceae) significantly mitigated the neurotoxicity induced by H2O2 in this screening system. Activity‐guided fractionation using several chromatographic techniques resulted in the isolation of the neuroprotective compound, cynandione A, a biacetophenone. At a concentration of 50 μM, cynandione A significantly reduced neurotoxicity induced by H2O2. Cynandione A significantly attenuated decreases in levels of glutathione, superoxide dismutase, and other enzymes that participate in the cellular defense against oxidative stress. Furthermore, cynandione A alleviated neurotoxicity induced by the excitotoxic neurotransmitter, L‐glutamate, the neurotoxicity induced by kainate, but not that mediated by N‐methyl‐D‐aspartate. Cynandione A was demonstrated to be a natural antioxidant as it facilitated the breakdown of hydrogen peroxide in vitro; however, no mechanism was uncovered to explain its neuroprotectant effects against glutamate and kainate. Therefore, cynandione A may be efficacious in protecting neurons from oxidative stress mediated via activation of α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionate/kainate receptors since it exerted significant neuroprotective effects on cultured cortical neurons. J. Neurosci. Res. 59:259–264, 2000

Lignans ofRosa multiflora roots

Five known lignans, (+)-pinoresinol (1), (+)-8-hydroxypinoresinol (2), (−)-dehydrodiconiferyl alcohol (3), (+)-trans-dehydrodiconiferyl alcohol (4), and (−)-olivil (5), were isolated from the roots ofRosa multiflora for the first time. Their structures were determined using spectroscopic data.

Protection of Rat Hepatocytes Exposed to CCl4 In‐vitro by Cynandione A, a Biacetophenone from Cynanchum wilfordii

To identify hepatoprotective agents from plant sources we use primary cultures of rat hepatocytes injured by CCl4. The hepatoprotective agents are the compounds that mitigate the injury caused by CCl4. Using this system we have investigated the biochemical mechanisms involved in the hepatoprotective activity of cynandione A, a biacetopherone, isolated from the roots of Cynanchum wilfordii Hemsley (Asclepiadaceae). Cynandione A (50 μm) significantly reduced (approximately 50%) the release into the culture medium of glutamic pyruvic transaminase and sorbitol dehydrogenase from the primary cultures of rat hepatocytes exposed to CCl4. Glutathione, superoxide dismutase, catalase and glutathione reductase play important roles in the cellular defence against oxidative stress. Cynandione A appeared to protect primary cultured rat hepatocytes exposed to CCl4 from significant drops in the levels of each of these four specific markers. Cynandione A also ameliorated lipid peroxidation by up to 50% as demonstrated by a reduction in the production of malondialdehyde.

Uncarinic acids: Phospholipase Cγ1 inhibitors from hooks of Uncaria rhynchophylla

Bioactivity-guided fractionation of the CHCl3 extract from hooks of Uncaria rhynchophylla led to the isolation of two triterpene esters, namely uncarinic acids A (1) and B (2). Their structures were established by spectroscopic and chemical methods. These compounds inhibited phospholipase Cgamma1 with IC50 values of 35.66 and 44.55 microM, respectively.

A-ring contracted triterpenoid from Rosa multiflora

Abstract A new A-ring contracted triterpene, rosamultic acid, was isolated from the roots of Rosa multiflora , together with five known triterpenes: sericic acid, euscaphic acid, myrianthic acid, kaji-ichigoside F1 and niga-ichigoside F2. The structure of the new compound was elucidated as 2-hydroxymethyl A(1)nor-19α,24-dihydroxyurs-2,12-dien-28-oic acid by spectroscopic methods.

Steroidal glycosides of the 14,15-seco-18-nor-pregnane series from Cynanchum ascyrifolium.

Three new steroidal glycosides named cynascyrosides A-C were isolated from the roots of Cynanchum ascyrifolium. The structures of these compounds were determined on the basis of spectroscopic and chemical evidence as cynajapogenin A 3-O-alpha-D-oleandropyranosyl-(1-->4)-beta-L-cymaropyranosyl -(1-->4)-beta-D- digitoxopyranoside; cynajapogenin A 3-O-beta-D-glucopyranosyl-(1-->4)-alpha-L-cymaropyranosyl- (1-->4)-beta-L-cymaropyranosyl-(1-->4)-beta-L-cymaropyranoside+ ++; cynajapogenin A 3-O-beta-D-glucopyranosyl-(1-->4)-alpha-L-cymaropyranosyl- (1-->4)-beta-D-digitoxopyranosyl-(1-->4)-beta-L-cymaropyranosid e.

A benzoquinone from Cynanchum wilfordii

Abstract A new amino-substituted p -benzoquinone was isolated from the roots of Cynanchum wilfordii , together with the five known acetophenones: 2′,5′-dihydroxyacetophenone, 4′-hydroxyacetophenone, 2′,4′-dihydroxyacetophenone, 4′-hydroxy-3′-methoxyacetophenone and cynandione A. The structure of new compound was elucidated as 2-acetyl-3,6-diamino-1,4-benzoquinone.

Enzymatic synthesis of a dihydrobenzofuran neolignan by oxidative coupling

The oxidative dimerization of ferulic acid has been carried out using horse-radish peroxidase as catalyst to give a dihydrobenzofuran neolignan (1), the structure of which was elucidated as (2SR, 3RS)-2,3-dihydro-2-(4-hydroxy-3-methoxyphenyl)-3-n-butoxycarbonyl-5-(2E-car-boxyethenyl)-7-methoxybenzofuran by spectroscopic analyses. This compound showed more potent cytotoxicity against several tumor cell lines than the starting material.

A new triterpene lactone from the roots ofPatrinia scabiosaefolia

A new triterpene lactone named patrinolide A (1) has been isolated from the roots ofPatrinia scabiosaefolia (Valerianaceae). Its structure was determined to be 11β,21β-dihydroxy-3-oxooleanan-28,13β-olide on the basis of spectral analysis, including 2D-NMR techniques.

A flavonoid diglycoside from Lepisorus ussuriensis.

Abstract A new flavonoid, quercetin 3-methyl ether 7-O-α- l -arabinofuranosyl (1→6)-β- d -glucopyranoside , was isolated from the whole plant of Lepisorus ussuriensis , together with four known flavonoids.