Jeong Seon Yoon

Neuroprotective Limonoids of Root Bark of Dictamnus dasycarpus

A methanolic extract of Dictamnus dasycarpus root bark afforded four new degraded limonoids, 9alpha-hydroxyfraxinellone-9- O-beta- d-glucoside ( 1), dictamnusine ( 2), dictamdiol A ( 3), and dictamdiol B ( 4), together with eight known compounds, dictamdiol ( 5), fraxinellone ( 6), fraxinellonone ( 7), 9beta-hydroxyfraxinellone ( 8), calodendrolide ( 9), obacunone ( 10), limonin ( 11), and rutaevin ( 12). Compounds, 2, 3, 6, 9, 10, and 11 showed significant neuroprotective activity against glutamate-induced neurotoxicity in primary cultures of rat cortical cells at a concentration of 0.1 microM.

Flavonoids from Spatholobus suberectus

Two pterocarpans [(6aR,11aR)-maackiain, (6aR,11aR)-medicarpin], one flavanone [(2S)-7-hydroxy-6-methoxy-flavanone], one isoflavan (sativan) and two isoflavones (pseudobaptige-nin, genistein) were isolated from theSpatholobus suberectus (Leguminosae). Their chemical structures were determined by comparison of their spectroscopic parameters of CD, EIMS, 1D-NMR and 2D-NMR with those reported in the literatures. All of these compounds are reported for the first time from this plant through the present study.

Iridoids from Scrophularia buergeriana attenuate glutamate-induced neurotoxicity in rat cortical cultures

In previous work, we isolated 7 neuroprotective iridoid glycosides from the 90% MeOH fraction of Scrophularia buergeriana (Scrophulariaceae). We therefore investigated the mode of action of 8‐O‐E‐p‐methoxycinnamoyl‐harpagide (8‐MCA‐Harp), the most potent neuroprotective iridoid, and its aglycone, harpagide (Harp) using primary cultures of rat cortical cells in vitro. 8‐MCA‐Harp only revealed its neuroprotective activity in a pretreatment paradigm; this iridoid had more selectivity in protecting neurons against N‐methyl‐D‐aspartate (NMDA)‐induced neurotoxicity as opposed to that induced by kainic acid (KA). On the other hand, Harp exerted significant neuroprotective activity when it was administered either before or after glutamate insult and protected cultured neuronal cells from neurotoxicity induced by NMDA or KA. Furthermore, Harp significantly prevented the decrease of glutathione, an antioxidative compound in the brain, in our cultures. Finally, 8‐MCA‐Harp and Harp could successfully reduce the overproduction of nitric oxide and the level of cellular peroxide in cultured neurons. Collectively, these results suggested that Harp and 8‐MCA‐Harp protected primary cultured neurons against glutamate‐induced oxidative stress primarily by acting on the antioxidative defense system and on glutamatergic receptors, respectively.

Antifibrotic activity of diterpenes from Biota orientalis leaves on hepatic stellate cells

Antifibrotic effect of twelve diterpenes (1–12) from the 90% methanolic fraction of Biota orientalis leaves was evaluated employing HSC-T6 cells by assessing cell proliferation and morphological change. Among these diterpenes, totarol (8) and isopimara-8(14),15-dien-19-oic acid (9) dramatically reduced cell proliferation in dose-and time-dependent manner. Furthermore, treatment with these compounds resulted in the different pattern of morphological changes of HSC-T6 cells. Taken together, antiproliferative activity of diterpenes from B. orientalis might suggest therapeutic potentials against liver fibrosis.

Inhibitory alkaloids from Dictamnus dasycarpus root barks on lipopolysaccharide-induced nitric oxide production in BV2 cells.

The methanolic extract of Dictamnus dasycarpus root barks afforded one new glycosidic quinoline alkaloid, 3-[1β-hydroxy-2-(β-D-glucopyranosyloxy)-ethyl)-4-methoxy-2(1H)-quinolinone (1), together with nine known compounds, preskimmianine (2), 8-methoxy-N-methylflindersine (3), dictamine (4), γ-fagarine (5), halopine (6), skimmianine (7), dictangustine-A (8), iso-γ-fagarine (9), isomaculosidine (10). The isolated alkaloids significantly inhibited nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated BV2 cells. Among them, compounds 3 and 7 showed the most potent inhibitory activities on LPS-induced NO production.