Phan Van Kiem

Two New Triterpene Glycosides from the Vietnamese Sea CucumberHolothuria scabra

Two new triterpene glycosides, namely holothurin A3 (1) and A4 (2) were isolated from the methanol extract of the sea cucumber,Holothuria scabra, with their structures elucidated from the spectroscopic evidence (1D NMR, 2D NMR, ESI-MS and HRESI-MS). Compounds1 and2 were found to be strongly cytotoxic to both cancer cell lines, KB and Hep-G2, with 50% inhibitory concentrations (IC50) of 0.87 and 0.32 μg/mL (for compound 1) and of 1.12 and 0.57 μg/mL (for compound2), respectively.

A new monoterpene glycoside from the roots of Paeonia lactiflora increases the differentiation of osteoblastic MC3T3-E1 cells

A new monoterpene glycoside, 6’-O-β-D-glucopyranosylalbiflorin (1), and four known compounds; albiflorin (2), 6’-O-benzoylalbiflorin (3), paeoniflorin (4) and benzoyl paeoniflorin (5), were isolated from the methanolic extract of the roots ofPaeonia lactiflora Pall.. Their chemical structures were completely elucidated using a combination of 2D NMR techniques (COSY, HMQC and HMBC) and HRESI-MS analyses. To investigate the bioactivities of these compounds, their effects on the differentiation of osteoblastic MC3T3-E1 cells were tested. Compound 1 (0.01-10 μM) significantly increased the alkaline phosphatase activity and nodules mineralization of MC3T3-E1 cells compared to those of the control (P<0.05). These results suggest that newly isolated compound 1 has a direct stimulatory effect on bone formationin vitro and may contribute to the prevention for osteoporosis.

Pentacyclic triterpenoids from Mallotus apelta.

A new triterpene (1) and six known pentacyclic terpenoids (2-7) were isolated from the methanol extract of the dried leaves fromMallotus apelta. Based on the spectral and chemical evidence, their structures were determined to be 3α-hydroxyhop-22(29)-ene (1), hennadiol (2), friedelin (3), friedelanol (4), epifriedelanol (5), taraxerone (6), and epitaraxerol (7).

Two new phenylpropanoid glycosides from the stem bark of Acanthopanax trifoliatus.

Two new phenylpropanoid glycosides, 1-β-D-glucopyranosyl-2,6-dimethoxy-4-propenylphenol (1) and 1-[β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl]-2,6-dimethoxy-4-propenylphenol (2) were isolated from the stem bark ofAcanthopanax trifoliatus along with four known compounds (3–6). Their structures were established on the basis of spectral and chemical evidences.

A new ursane-type triterpenoid glycoside from Centella asiatica leaves modulates the production of nitric oxide and secretion of TNF-α in activated RAW 264.7 cells.

One new ursane-type triterpenoid glycoside, asiaticoside G (1), five triterpenoids, asiaticoside (2), asiaticoside F (3), asiatic acid (4), quadranoside IV (5), and 2α,3β,6β-trihydroxyolean-12-en-28-oic acid 28-O-[α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl] ester (6), and four flavonoids, kaempferol (7), quercetin (8), astragalin (9), and isoquercetin (10) were isolated from the leaves of Centella asiatica. Their chemical structures were elucidated by mass, 1D- and 2D-nuclear magnetic resonance (NMR) spectroscopy. The structure of new compound 1 was determined to be 2α,3β,23,30-tetrahydroxyurs-12-en-28-oic acid 28-O-[α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl] ester. The anti-inflammatory activities of the isolated compounds were investigated on lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. Asiaticoside G (1) potently inhibited the production of nitric oxide and tumor necrosis factor-α with inhibition rates of 77.3% and 69.0%, respectively, at the concentration of 100 μM.

C29 sterols with a cyclopropane ring at C-25 and 26 from the Vietnamese marine sponge Ianthella sp. and their anticancer properties.

Two new C(29) sterols with a cyclopropane ring at C-25 and C-26, petrosterol-3,6-dione (1) and 5alpha,6alpha-epoxy-petrosterol (2), along with petrosterol (3), were isolated from the Vietnamese marine sponge Ianthella sp. The structures of the new compounds were elucidated by comprehensive spectroscopic analyses. Compounds 1-3 showed cytotoxic activities on A549, HL-60, MCF-7, SK-OV-3, and U937 cancer cell lines with IC(50) in the range of 8.4-22.6 microM, whereas compounds 1-3 exhibited only weak cytotoxic activities on HT-29 cell. After HL-60 cells were treated with the compounds, several apoptosis events like chromatin condensation and the increase of the population of sub-G1 hypodiploid cells were observed. These data supported that the compounds might have potential for leukemia treatment.

New monoterpene glycosides from Paeonia lactiflora

Three new monoterpene glycosides named 4-O-methyl-paeoniflorin (1), isopaeoniflorin (2), and isobenzoylpaeoniflorin (3), together with two known monoterpene glycosides, paeoniflorin (4) and benzoylpaeoniflorin (5), were isolated from the roots of Paeonia lactiflora. Their structures were established on the basis of spectral and chemical evidence.

Anti-inflammatory asterosaponins from the starfish Astropecten monacanthus.

Four new asterosaponins, astrosteriosides A-D (1-3 and 5), and two known compounds, psilasteroside (4) and marthasteroside B (6), were isolated from the MeOH extract of the edible Vietnamese starfish Astropecten monacanthus. Their structures were elucidated by chemical and spectroscopic methods including FTICRMS and 1D and 2D NMR experiments. The effects of the extracts and isolated compounds on pro-inflammatory cytokines were evaluated by measuring the production of IL-12 p40, IL-6, and TNF-α in LPS-stimulated bone marrow-derived dendritic cells. Compounds 1, 5, and 6 exhibited potent anti-inflammatory activity comparable to that of the positive control. Further studies are required to confirm efficacy in vivo and the mechanism of effects. Such potent anti-inflammatory activities render compounds 1, 5, and 6 important materials for further applications including complementary inflammation remedies and/or functional foods and nutraceuticals.

Cytotoxic and anti-inflammatory cembranoids from the Vietnamese soft coral Lobophytum laevigatum

Four new cembranoids, namely laevigatol A-D (1-4), and six known metabolites (5-10), were isolated from the Vietnamese soft coral Lobophytum laevigatum. The structures of these compounds were elucidated by extensive spectroscopic analyses, and the absolute stereochemistry of 1 was determined using the modified Moshers method. Compounds 5, and 7-10 exhibited cytotoxic activity against selected human cancer cell lines. Compounds 1, 2, 8, and 9 showed dose-dependent inhibitory effects on the TNFα-induced NF-κB transcriptional activity in Hep-G2 cells. Moreover, compounds 1, 2, 8, and 9 significantly inhibited the induction of COX-2 and iNOS mRNA dose-dependently, indicating that these compounds attenuated the synthesis of these transcripts at the transcriptional level.

Oleanane-type triterpene saponins from the bark of Aralia elata and their NF-κB inhibition and PPAR activation signal pathway.

Two new oleanane-type triterpene saponins, tarasaponin IV (1) and elatoside L (2), and four known; stipuleanoside R(2) (3), kalopanax-saponin F (4), kalopanax-saponin F methylester (5), and elatoside D (6) were isolated from the bark of Aralia elata. Kalopanax-saponin F methyl ester was isolated from nature for the first time. Their chemical structures were elucidated using the chemical and physical methods as well as good agreement with those of reported in the literature. Oleanane-type triterpene saponins are the main component of A. elata. All compounds were investigated the anti-inflammatory activity. We measured their inhibition of NF-κB and activation of PPARs activities in HepG2 cells using luciferase reporter system. As results, compounds 2 and 4 were found to inhibit NF-κB activation stimulated by TNFα in a dose-dependent manner with IC(50) values of 4.1 and 9.5 μM, respectively, when compared with that of positive control, sulfasalazine (0.9 μM). Compounds 2 and 4 also inhibited TNFα-induced expression of iNOS and COX-2 mRNA. Furthermore, compounds 1-6 were evaluated PPAR activity using PPAR subtype transactivation assays. Among of them, compounds 4-6 significantly increased PPARγ transactivation. However, compounds 4-6 did not activate in any other PPAR subtypes.