Soo-Jin Choo

Free radical scavenging and antielastase activities of flavonoids from the fruits of Thuja orientalis

Bioassay-guided fractionation of the MeOH extract of Thuja orientalis fruits using a DPPH (2,2-diphenyl-1-picrylhydrazyl) assay led to the isolation of 9 flavonoids: cupressuflavone (1), amentoflavone (2), robustaflavone (3), afzelin (4), (+)-catechin (5), quercitrin (6), hypolaetin 7-O-β-xylopyranoside (7), isoquercitrin (8) and myricitrin (9). Their chemical structures were determined by spectroscopic analyses. The free radical scavenging and human neutrophil elastase (HNE) inhibitory activities were evaluated for the isolated compounds. By DPPH scavenging assay, compounds 5, 6, 7, 8 and 9 showed anti-oxidant activities with IC50 values of 28.66, 31.19, 18.30, 26.63 and 15.10 μM, respectively. By ABTS [2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt] scavenging assay, these compounds also exhibited potent anti-oxidant activities with IC50 values of 6.77, 13.96, 6.97, 22.79 and 9.96 μM, respectively. Of note, compounds 1, 2 and 3 showed significant HNE inhibitory activities with IC50 values of 8.09, 1.27 and 1.33 μM, respectively.

Evaluation of human neutrophil elastase inhibitory effect of iridoid glycosides from Hedyotis diffusa.

Five iridoid glycosides were isolated from the MeOH extract of Hedyotis diffusa, and their structures were elucidated as E-6-O-p-methoxycinnamoyl scandoside methyl ester (1), Z-6-O-p-methoxycinnamoyl scandoside methyl ester (2), E-6-O-p-feruloyl scandoside methyl ester (3), E-6-O-p-coumaroyl scandoside methyl ester (4), and Z-6-O-p-coumaroyl scandoside methyl ester (5) by interpretation of their spectroscopic data. All the isolated compounds were evaluated for human neutrophil elastase inhibitory effect, and compound 1 showed potent activity with an IC(50) value of 18.0muM. The molecular docking simulation suggested a structural model for the inhibition of human neutrophil elastase by compound 1.

Chemical constituents from the leaves of Ilex paraguariensis inhibit human neutrophil elastase

Human neutrophil elastase (HNE), a serine protease with broad target specificity, is the only enzyme responsible for the degradation of elastin which is an insoluble elastic fibrous protein in animal connective tissue. Biologically, elastase activity significantly increased with age, which results in a reduced skin elasticity and in the appearance of wrinkles or stretchmarks. In the course of our screening program for HNE inhibitors from natural source, the MeOH extract of Ilex paraguariensis leaves showed strong HNE inhibitory effect. Bioassay-guided fractionation led to the isolation of a new pyrrole alkaloid (1), along with seventeen known compounds (2–18) from the MeOH extract of Ilex paraguariensis leaves, and their chemical structures were elucidated on the basis of spectroscopic analysis. All isolated compounds were evaluated for HNE inhibitory activity, and the result demonstrated that dicaffeoylquinic acid derivatives (12, 13, 14, 15 and 16) and flavonoids (8 and 17) exhibited potent HNE inhibitory activity with IC50 values ranging from 1.4 to 7.3 µM.

Lanostane triterpenes from Ganoderma lucidum suppress the adipogenesis in 3T3-L1 cells through down-regulation of SREBP-1c

Several lanostane triterpenes [butyl ganoderate A (1), butyl ganoderate B (2), butyl lucidenate N (3), and butyl lucidenate A (4)] bearing a butyl ester side chain from the fruiting bodies of Ganoderma lucidum exhibited considerable inhibitory effects on adipogenesis in 3T3-L1 cells. The inhibitory mechanism of 1 and 3 on adipogenesis in 3T3-L1 cells was investigated; we found that the mRNA and protein expression levels of SREBP-1c were reduced by treatment with 1 and 3 versus the untreated control. Furthermore, compounds 1 and 3 suppressed the mRNA expression levels of FAS and ACC. These results demonstrate that inhibition of adipogenesis in 3T3-L1 cells by treatment with 1 and 3 may be mediated in part through down-regulation of the adipogenic transcription factor SREBP-1c and its target genes, such as FAS and ACC.

Etoposide-resistant HT-29 human colon carcinoma cells during glucose deprivation are sensitive to piericidin A, a GRP78 down-regulator

Glucose deprivation, a pathophysiological cell condition, causes up‐regulation of GRP78 and induction of etoposide resistance in human cancer cells. The induction of drug resistance can be partly explained by the fact that GRP78 can block activation of caspase‐7 induced by treatment with etoposide. Therefore, downregulating GRP78 expression may be a novel strategy anticancer drug development. Based on that premise, we established a screening program for anticancer agents that exhibit preferential cytotoxic activity for etoposide‐resistant cancer cells under glucose‐deprived conditions. We recently isolated an active compound, AR‐054, from the culture broth of Streptomyces sp., which prevents stress‐induced etoposide resistance in vitro. AR‐054 was identified as piericidin A, a prototypical compound, by ESI‐MS analysis and various NMR spectroscopic methods. Here, we showed that piericidin A suppressed the accumulation of GRP78 protein and was also highly toxic to etoposide‐resistant HT‐29 cells, with IC50 values for colony formation of 6.4 and 7.7 nM under 2‐deoxyglucose supplemented and glucose‐deprived conditions, respectively. Interestingly, piericidin A had no effect under normal growth conditions. Therefore, we suggest that piericidin A prevents up‐regulation of GRP78, and exhibits cytotoxicity in glucose‐deprived HT‐29 cells that are resistant to etoposide. J. Cell. Physiol. 215: 243–250, 2008.

Deoxyverrucosidin, a novel GRP78/BiP down-regulator, produced by Penicillium sp

Glucose-regulated protein 78 (GRP78) resides in endoplasmic reticulum (ER) and plays a role in protecting tumor cells against the toxic effects of anticancer agents. During the search for down-regulators of GRP78 using a reporter gene (luciferase) assay system, we isolated a novel compound designated as deoxyverrucosidin (1), a congener of verrucosidin (2), from Penicillium sp. and identified it as a down-regulator of the grp78 gene. The structure of 1 was determined by mainly ESI-mass and two-dimensional NMR spectra. 1 dose-dependently inhibited the expression of GRP78 promoter with an IC50 of 30 nM.

Silymarin inhibits melanin synthesis in melanocyte cells

Objectives The aim was to search for inhibitors of melanogenesis from natural resources.

Eudesmanolides from Taraxacum mongolicum and their inhibitory effects on the production of nitric oxide.

A new eudesmanolide, 1β,3β-dihydroxy-eudesman-11(13)-en-6α,12-olide (1) was isolated and identified from Taraxacum mongolicum, together with two known compounds, 1β,3β-dihydroxyeudesman-6α,12-olide (2) and loliolide (3). The structure of 1 was established by analysis of its physical and spectroscopic data. 1 was found to have an inhibitory activity on nitric oxide production with an IC50 of 38.9 μM in activated RAW 264.7 cells.

Hypopigmentary action of dihydropyranocoumarin D2, a decursin derivative, as a MITF-degrading agent.

In this study, the decursin derivative dihydropyranocoumarin D2 (1) was selected for its effects on melanogenesis using a spontaneously immortalized mouse melanocyte cell line (Mel-Ab). The results showed that 1 effectively inhibited melanin synthesis in a concentration-dependent manner, but that it did not inhibit tyrosinase in a cell-free system. In addition, the changes in ERK, Akt, and microphthalmia-associated transcription factor (MITF) in response to treatment with 1 were assessed. The results revealed that ERK was dramatically up-regulated and MITF was down-regulated in response to treatment with 1, but that Akt was unchanged. Therefore, the effects of 1 on melanogenesis were examined in the absence or presence of PD98059 (a specific inhibitor of the ERK pathway). PD98059 restored hypopigmentation and the down-regulation of MITF induced by 1. Finally, MITF down-regulation by 1 was clearly restored by both chloroquine, a lysosomal proteolysis inhibitor, and MG132, a proteasome inhibitor.

A New Antioxidant, Clitocybin A, from the Culture Broth of Clitocybe aurantiaca

Clitocybin A (1), a new antioxidant, was isolated from the culture broth of Clitocybe aurantiaca. This compound was purified by solvent extraction, silica gel column chromatography, Sephadex LH-20 column chromatography and preparative HPLC. Its structure was determined as 4,6-dihydroxy-2-ρ-hydroxyphenyl-isoindol-1-one on the basis of the UV, NMR, and MS spectroscopic analysis. The compound 1 showed potent free radical scavenging activity against superoxide, ABTS, and DPPH radicals, and protective effect against cellular DNA damage induced by oxidative stress.