Nam-In Baek

Flavonoids from the buds of Rosa damascena inhibit the activity of 3-hydroxy-3-methylglutaryl-coenzyme a reductase and angiotensin I-converting enzyme.

Rosa damascena has been manufactured as various food products, including tea, in Korea. A new flavonoid glycoside, kaempferol-3-O-beta-D-glucopyranosyl(1-->4)-beta-D-xylopyranoside, named roxyloside A was isolated from the buds of this plant, along with four known compounds, isoquercitrin, afzelin, cyanidin-3-O-beta-glucoside, and quercetin gentiobioside. The chemical structures of these compounds were determined by spectroscopic analyses, including FAB-MS, UV, IR, (1)H and (13)C NMR, DEPT, and 2D NMR (COSY, HSQC, and HMBC). All the isolated compounds except cyanidin-3-O-beta-glucoside exhibited high levels of inhibitory activity against 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase with IC(50) values ranging from 47.1 to 80.6 microM. Cyanidin-3-O-beta-glucoside significantly suppressed angiotensin I-converting enzyme (ACE) activity, with an IC(50) value of 138.8 microM, while the other four compounds were ineffective. These results indicate that R. damascena and its flavonoids may be effective to improve the cardiovascular system.

Anti-pruritic effect of baicalin and its metabolites, baicalein and oroxylin A, in mice

AbstractAim:To explore whether intestinal microflora plays a role in anti-pruritic activity of baicalin, a main constituent of the rhizome of Scutellaria baicalensis (SB).Methods:Baicalin was anaerobically incubated with human fecal microflora, and its metabolites, baicalein and oroxylin A, were isolated. The inhibitory effect of baicalin and its metabolites was accessed in histamine- or compound 48/80-induced scratching behavior in mice.Results:Baicalin was metabolized to baicalein and oroxylin A, with metabolic activities of 40.2±26.2 and 1.2±1.1 nmol·h−1·mg−1 wet weight of human fecal microflora, respectively. Baicalin (20, 50 mg/kg) showed more potent inhibitory effect on histamine-induced scratching behavior when orally administered than intraperitoneally. In contrast, baicalein and oroxylin A had more potent inhibitory effect when the intraperitoneally administered. The anti-scratching behavior activity of oral baicalin and its metabolites was in proportion to their inhibition on histamine-induced increase of vascular permeability with oroxylin A more potent than baicalein and baicalin. In Magnus test using guinea pig ileum, oroxylin A is more potent than baicalein and baicalin in inhibition of histamine-induced contraction. The anti-scratching behavioral effect of oral baicalin was significantly reduced when oral antibiotics were simultaneously administered, whereas the effect of baicalein and oroxylin A were not affected.Conclusion:Oral baicalin may be metabolized by intestinal microflora into baicalein and oroxylin A, which ameliorate pruritic reactions through anti-histamine action.

Stewartia koreana extract stimulates proliferation and migration of human endothelial cells and induces neovasculization in vivo

Angiogenesis, the growth of new blood vessels from preexisting vasculature, plays an important role in physiological and pathological processes such as embryonic development and wound healing. This study investigated the effects of methanol extracts of Stewartia koreana leaves (SKE) on angiogenesis. Stewartia koreana significantly promoted the proliferation and migration of human umbilical vein endothelial cells in a dose‐dependent manner. The SKE induced endothelial cell proliferation in the range of 50 µg/mL without cytotoxicity. Treatment of HUVECs resulted in the activation of the mitogen‐activated protein kinases that was correlated with endothelial cell proliferation and migration. SKE also stimulated angiogenesis in a chick chorioallantoic membrane assay, demonstrating promotion of new blood vessel formation in vivo. Local administration of SKE onto skin punched wounds resulted in increased von Willebrand Factor antigen, indicating that it stimulated neovasculization in the wound region. The results suggest that Stewartia koreana extracts may potentially be useful for the development of agents to accelerate vascular wound healing or to promote the growth of collateral blood vessels in ischemic tissues. Copyright

CYTOTOXIC TRITERPENOIDS FROM Cornus kousa FRUITS

Cornus kousa Burg. (Cornaceae) is a small deciduous tree characterized by brilliant, colorful, and attractive flowers and fruits. It is widely distributed in the northern hemisphere, such as eastern Asia and eastern and northern parts of the United States. C. kousa is widely cultivated for ornamental purposes in eastern Asia. The fruits of this plant have been used as a hemostatic agent and for the treatment of diarrhea in Korean traditional medicine [1]. Additionally, immuno-regulatory properties for this fruit extract have been reported [2]. Some chemical constituents such as isoquercitrin, gallic acid, tannin, phenolics, and flavonoids [3] have been reported to be present in the leaves of C. kousa. Also, our previous phytochemical research on the fruits of this plant demonstrated the presence of steroids [4], cytotoxic lignans [5], and flavonoids [6]. Bioactivity-guided fractionation led to the isolation of cytotoxic triterpenoids from the fruits of C. kousa. When the methanol extracts of C. kousa were developed on silica gel TLC, pink and purple spots appeared after spraying with 10% H2SO4 solution and heating, indicating the presence of triterpenoids in the extracts. The methanol extract was fractionated into an EtOAc layer, an n-BuOH layer, and a H2O layer through solvent fractionation. The repeated silica gel (SiO2), octadecyl silica gel (ODS), and Sephadex LH-20 column chromatographies (c.c.) of EtOAc fractions yielded ten triterpenoids, compounds 1–10. The chemical structures of the triterpenoids were determined from spectroscopic analysis, including EI/FAB-MS, IR, PMR, 13C NMR, DEPT, and 2D NMR (COSY, HSQC, HMBC). The compounds were revealed to be ursolic acid (1) [7], lupeol (2) [8], taraxasterol (3) [9], betulinic acid (4) [10], betulinic aldehyde (5) [11], ursolic aldehyde (6) [7], arjunolic acid (7) [12], tormentic acid (8) [13], asiatic acid (9) [14], and 19 -hydroxyasiatic acid (10) [15]. Although these compounds were previously isolated from other plants, this is the first report of their isolation from C. kousa. All isolated compounds were evaluated for their cytotoxicity against human colon carcinoma (HCT-116), human breast carcinoma (MCF-7), human cervix carcinoma (HeLa), human ovary carcinoma (SK-OV-3), and human melanoma (SK-MEL-5) using the MTT assay. As shown in Table 2, some compounds inhibited the growth of human cancer cell lines. In conclusion, the findings of this study suggest that the methanolic extract of C. kousa, as well as its isolated triterpenoids, may prove useful for the treatment of human cancer. Plant Materials. The fruits of Cornus kousa Burg. (Cornaceae) were collected at the experimental farm at Kyung Hee University in August 2006 and identified by Prof. Dae-Keun Kim, College of Pharmacy, Woosuk University, Jeonju, Korea. A voucher specimen (KHU060907) was reserved at the Laboratory of Natural Products Chemistry, Kyung Hee University, Yongin, Korea.

Cytotoxic germacranolide sesquiterpenes from the bark of Magnolia kobus.

A new (3) and three known germacrane-type sesquiterpenoids were isolated from the chloroform-soluble fraction of the methanolic extract of the bark of Magnolia kobus (Magnoliaceae) through repeated silica gel and Sephadex LH-20 column chromatography. Their chemical structures were elucidated as costunolide (1), parthenolide (2), isobisparthenolidine (3), and bisparthenolidine (4) by spectroscopic analysis. Compounds 1–4 exhibited cytotoxicity against human A549, SK-OV-3, SK-MEL-2, and HCT15 tumor cells.

In vitro metabolism of Jaceosidin and characterization of cytochrome P450 and UDP-glucuronosyltransferase enzymes in human liver microsomes.

Jaceosidin is an active component in Artemisia species as well as Eupatorium species and it exhibits antiallergic, anticancer, antioxidant, anti-inflammatory, and antimutagenic activities. Jaceosidin was metabolized to jaceosidin glucuronide, 6-O-desmethyljaceosidin, hydroxyjaceosidin, 6-O-desmethyljaceosidin glucuronide, and hydroxyjaceosidin glucuronide in human liver microsomes. This study characterized the human liver cytochrome P450 (CYP) and UDPglucuronosyltransferase (UGT) enzymes responsible for the metabolism of jaceosidin. CYP1A2 was identified as the major enzyme responsible for the formation of 6-O-desmethyljaceosidin and hydroxyjaceosidin from jaceosidin on the basis of a combination of correlation analysis and experiments including immuno-inhibition, chemical inhibition in human liver microsomes, and metabolism by human cDNA-expressed CYP enzymes. Jaceosidin glucuronidation was catalyzed by UGT1A1, UGT1A3, UGT1A7, UGT1A8, UGT1A9, and UGT1A10. These results suggest that the pharmacokinetics of jaceosidin may be dramatically affected by polymorphic CYP1A2, UGT1A1, and UGT1A7 responsible for the metabolism of jaceosidin or by the coadministration of relevant CYP1A2 or UGT inhibitors or inducers.

Simultaneous suppression of three genes related to brassinosteroid (BR) biosynthesis altered campesterol and BR contents, and led to a dwarf phenotype in Arabidopsis thaliana.

We generated transgenic lines of Arabidopsis thaliana with an RNA interference construct that expressed hairpin double-stranded RNA for DET2:DWF4:SMT2 to induce sequence-specific RNA silencing. In transgenic plants, expressions of DET2, DWF4, and SMT2 were simultaneously reduced, and the campesterol content was increased by up to 420% compared to the level in the wild-type plant. Triple knock-down of the DET2, DWF4, and SMT2 enzymes also resulted in reduction of brassinosteroid (BR)-specific biosynthesis intermediates. Transgenic plants harboring the RNA interference construct displayed a semi-dwarf phenotype due to altered development. Our findings indicate that redesigning of plant architecture is possible through simultaneous suppression of multiple genes involved in BR biosynthesis.

Screening and isolation of a natural dopamine D1 receptor antagonist using cell-based assays.

To develop a cell-based assay to screen for human dopamine D(1) receptor agonists or antagonists from medicinal plant extracts, a stable Chinese hamster ovary (CHO) cell line (CHO-D1R) expressing the human dopamine D(1) receptor was established using an expression vector containing a scaffold attachment region (SAR) element. CHO-D1R cells showed specific binding to [(3)H]-SCH23390 with high affinity (K(d)=1.47+/-0.17 nM) and dose-dependent responses for the dopamine-mediated stimulation of cAMP concentrations (EC(50)=20.6+/-1.44 nM). The screening of medicinal plant extracts using cell-based cAMP assays revealed that an extract of Gleditsia sinensis Lam., which is known to be rich in saponin, had strong antagonist activity for the D(1) receptor. From the activity-guided fractionation and chemical structural analysis of the G. sinensis extract, a compound called gleditsioside F was isolated and was identified to have antagonist activity for the D(1) receptor. Gleditsioside F showed very effective D(1) antagonist activity by inhibiting ligand binding to the D(1) receptor as well as by inhibiting dopamine-mediated increases in cAMP concentration.

A new phenolic glycoside from the fruits of Capsicum annuum

A new compound, 4-O-(6-O-p-hydroxybenzoyl-β-D-glucopyranosyl)-cis-p-coumaric acid, was isolated from the fruits of hot pepper (Capsicum annuum L.). The structure of the compound was established on the basis of NMR, FAB-MS, and IR spectroscopic data.