Bui Huu Tai

Chemical constituents of Miliusa balansae leaves and inhibition of nitric oxide production in lipopolysaccharide-induced RAW 264.7 cells.

Methanolic extract of Miliusa balansae Finet et Gagnep exerts an anti-inflammatory effect via inhibition of nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated murine RAW 264.7 macrophage cells. Three new megastigmane glycosides, milbasides A-C (1-3), together with fifteen known compounds (4-18), were isolated from the active fraction. Their chemical structures were elucidated using extensive spectroscopic analyses, including 1D and 2D NMR, HR ESI MS, and CD analysis, as well as comparison with previously reported data. Compounds 1-3, 11 and 14 (20.0 μM) showed potent inhibitory activities with inhibition values of 98.5 ± 1.6%, 90.9 ± 7.8%, 84.8 ± 3.5%, 91.5 ± 8.7%, and 91.8 ± 2.7%, respectively. Our results suggest that megastigmane glycosides from M. balansae leaves may be used to treat inflammatory diseases.

Studies on the acetylation and NMR reassignment of indirubin derivatives

The analysis of 1D- and 2D-NMR spectroscopic data confirmed that the amino N-1′ protons of indirubin and indirubin-3′-oxime resonate at a higher frequency than N-1 protons. The amino N-1′ protons in both indirubin and indirubin-3′-oxime are not favourable for acetylated reaction due to their intramolecular hydrogen bonding with the amide carbonyl group. The new N-1-acetylindirubin-3′-acetoxime has been synthesised using acetic anhydride. The reassignment of the NMR data of indirubin, indirubin-3′-oxime and N-1-acetylindirubin was confirmed with the aid of DEPT, HSQC, HMBC and NOESY methods.

Prenylated isoflavones from Cudrania tricuspidata inhibit NO production in RAW 264.7 macrophages and suppress HL-60 cells proliferation

Abstract Inhibitory effects of NO production in RAW 264.7 macrophages guided the isolation of nine prenylated isoflavones, including a new cudraisoflavone L (1) and eight known metabolites furowanin B (2), erysubin A (3), wighteone (4), lupalbigenin (5), laburnetin (6), isolupalbigenin (7), 6,8-diprenylorobol (8), millewanin H (9) from the leaves of Cudrania tricuspidata. At the concentration of 10 μM, compounds 1, 2, and 4 significantly inhibited NO production with the inhibitory values of 72.5 ± 2.4, 66.9 ± 1.8, and 55.4 ± 2.7%, respectively. In addition, all of isolated compounds 1–9 showed promising cytotoxic effects toward HL-60 cells (IC50 4.3 ± 0.7 to 18.0 ± 1.7 μM).

Oleanane-type saponins from Glochidion glomerulatum and their cytotoxic activities

Eight oleanane-type saponins, glomerulosides A-H, were isolated from leaves of Glochidion glomerulatum. All isolated compounds were evaluated for cytotoxic activity on four human cancer cell lines, A-549, HT-29, OVCAR, and MCF-7. Glomerulosides C and E, which contain a benzoyloxy group at C-22, showed significant cytotoxic activities against the A-549, HT-29, and OVCAR cancer cell lines with IC50 values ranging from 5.9 to 9.8μM. Glomeruloside A showed cytotoxicity on HT-29 and OVCAR cell lines with IC50 values of 7.3 and 6.6μM, respectively. Moreover, glomeruloside B exhibited significant activity on A-549 and HT-29 cancer cell lines with IC50 values of 9.7 and 7.5μM. In contrast, glomerulosides F-H, lacking a benzoyloxy group, showed only moderate cytotoxic activity.

Sesquiterpene derivatives from marine sponge Smenospongia cerebriformis and their anti-inflammatory activity

Using various chromatographic methods, five new sesquiterpene derivatives named smenohaimiens A-E (1-5) and five known, 19-hydroxy-polyfibrospongol B (6), ilimaquinone (7), dictyoceratin C (8), polyfibrospongol A (9), and polyfibrospongol B (10) were isolated from the marine sponge Smenospongia cerebriformis Duchassaing & Michelotti, 1864. Their structures were assigned by 1D, 2D NMR spectroscopic analysis, HR ESI MS, and calculations of the electron circular dichroism spectra. All compounds were evaluated for the inhibitory activity against NO production in lipopolysaccharide-stimulated in BV2 microglia cells. As the results, compound 7 significantly inhibited NO production with the IC50 value of 10.40±1.28µM. The remaining compounds showed moderate inhibitory NO production activities with IC50 values ranging from 24.37 to 30.43µM.

Spirostanol saponins from Tacca vietnamensis and their anti-inflammatory activity.

Using various chromatographic methods, five new steroidal saponins named taccavietnamosides A-E (1-5) and three known, (24S,25R)-spirost-5-en-3β,24-diol 3-O-α-l-rhamnopyranosyl-(1→2)-[α-l-rhamnopyranosyl-(1→3)]-β-d-glucopyranoside (6), (24S,25R)-spirost-5-en-3β,24-diol 3-O-α-l-rhamnopyranosyl-(1→2)-[β-d-glucopyranosyl-(1→4)-α-l-rhamnopyranosyl-(1→3)]-β-d-glucopyranoside (7), and chantrieroside A (8) were isolated from the rhizomes of Tacca vietnamensis Thin et Hoat. Their chemical structures were elucidated by physical and chemical methods. All compounds were evaluated for the inhibitory activities of nitric oxide production in LPS-stimulated RAW 264.7 macrophages and BV2 cells. As the results, compounds 3-5 showed moderate inhibition on NO production in LPS-stimulated BV2 cells and RAW 264.7 macrophages with the IC50 values ranging from 37.0 to 60.7μM.

1)H and (13)C NMR assignments of sesquiterpenes from Dysidea fragilis.

Sesquiterpenes have been reported as components of the genus Dysidea (Dysideidae). Many chemical investigations have been focused on the marine sponge Dysidea fragilis. The constituents of D. fragilis were identified as sesquiterpenes, steroids and diketopiperazines. They exhibited various biological activities such as anti-inflammatory and cytotoxic activities. Previously, series of new sesquiterpenes were reported from the Vietnamese sponge D. cinerea by our group. In continuing research on bioactive compounds from genus Dysidea, three new and two known sesquiterpenes were isolated from the sponge D. fragilis. Herein, we report the isolation and structure elucidation of these compounds.

Steroidal saponins from Datura metel

&NA; Datura metel L. (Solanaceae) is an annual herb that has been widely used in the traditional medicine for the treatment of coughs, bronchial asthma, and rheumatism. Chemical investigation of an acidic methanol extract of the whole plants of D. metel resulted in the isolation of five new steroidal saponins (1–3, 5, and 6), named metelosides A‐E, and four known compounds (4, 7–9). Their structures were elucidated by extensive spectroscopic methods, including 1D and 2D NMR and MS spectra. The structures of metelosides A and B were found to be unusual among the reported spirostane‐type steroidal saponins due to the presence of the acetamide groups in the molecules. Compounds 2, 4, 5, and 6 were shown to be cytotoxic against three cancer cell lines, including HepG2, MCF‐7, and SK‐Mel‐2 cells. Furthermore, compounds 3, 4, and 7 exhibited modest anti‐inflammatory effects through inhibition of NO production in LPS‐stimulated BV cells. Graphical abstract Figure. No caption available. HighlightsNine compounds were isolated from Datura metel.The structures of five new steroidal saponins and 4 known compounds were identified by spectroscopic methods.Four compounds were cytotoxic against HepG2, MCF‐7, and SK‐Mel‐2 cells.Three compounds inhibited NO production in LPS‐stimulated BV cells.

Naphtoquinones and Sesquiterpene Cyclopentenones from the Sponge Smenospongia cerebriformis with Their Cytotoxic Activity

Two new naphtoquinones (smenocerones A and B, 1 and 2) and four known sesquiterpene cyclopentenones (dactylospongenones A-D, 3-6) were isolated from sponge Smenospongia cerebriformis living in the Eastern Sea of Vietnam. Their chemical structures were determined by high resolution electrospray ionization (HR-ESI)-MS, NMR spectroscopic analysis, and in comparison with the reported data. The chiroptical properties of compounds 3-6 were examined by experiment and theoretical calculation of circular dichroism (CD) spectra to prove their absolute configurations. Compound 2 significantly exhibited cytotoxic activity towards lung carcinoma (LU-1), hepatocellular carcinoma (HepG-2), promyelocytic leukemia (HL-60), breast carcinoma (MCF-7), and melanoma (SK-Mel-2) human cancer cells with IC50 values of 5.5±0.8, 3.2±0.2, 4.0±0.7, 4.1±0.8, and 5.7±1.1 µg/mL, respectively.

Macrolide and phenolic metabolites from the marine-derived fungus Paraconiothyrium sp. VK-13 with anti-inflammatory activity

Five new secondary metabolites, modiolides D-G (1−4) and 1-(2,5-dihydroxyphenyl)-3-methoxy-butan-1-one (8), one new natural product, 1-(2,5-dihydroxyphenyl)-3-hydroxybutan-1-one (7), along with three known compounds, modiolides A (5) and B (6), and 1-(2,5-dihydroxyphenyl)-2-buten-1-one (9) were isolated from a fermentation culture of the marine endophytic fungus Paraconiothyrium sp. VK-13. Their chemical structures were elucidated by the NMR and MS spectroscopic analysis as well as the modified Mosher’s method. Compounds 7 and 9 inhibited the overproduction of proinflammatory mediators NO and PGE2 in LPS-stimulated RAW264.7 cells, with IC50 values ranging from 3.9 to 12.5 µM. The inhibitory effects of 7 and 9 on the release of NO and PGE2 were correlated with their significant suppression of iNOS and COX-2 protein expression, respectively. Furthermore, both compounds 7 and 9 inhibited the mRNA expression of proinflammatory cytokines, including TNF-α, IL-1β, IL-6, and IL-12, with IC50 values in a range of 2.4−12.5 µM.