Dang Ngoc Quang

Iridoid glucosides from roots of Vietnamese Paederia scandens.

Four iridoid glucosides, three of which are dimeric were isolated from the methanol extract of roots of Vietnamese Paederia scandens (Lour) Merrill together with the five known glucosides, paederoside, asperuloside, paederosidic acid, asperulosidic acid and geniposide. Seven sulfur-containing iridoid glucosides were also isolated. The structures of the iridoid glucosides were determined by a combination of high-resolution NMR, MS, IR and UV spectra, and chemical reaction such as acetylation.

Thelephantins D-H: Five p-terphenyl derivatives from the inedible mushroom Thelephora aurantiotincta

Five p-terphenyl derivatives named thelephantins D-H (1-5) together with nine known compounds, thelephantins A-C (6-8), ganbajunin E (9), p-hydroxylbenzoic acid (10), ganbajunin C (11), thelephorin A (12), 2-O-methylatromentin (13) and atromentin (14), were isolated from the methanolic extract of fruit bodies of the Thelephoraceous Basidiomycete Thelephora aurantiotincta. Their structures were elucidated by high-resolution MS, 2D NMR, IR and UV spectroscopic analysis.

Concentriols B, C and D, three squalene-type triterpenoids from the ascomycete Daldinia concentrica

Three squalene-type triterpenoids named concentricols B, C and D (1-3) were isolated from the ethyl acetate extract of fruiting bodies of the xylariaceous ascomycete Daldinia concentrica. Their absolute structures were elucidated by analysis of 2D NMR, MS, IR and UV spectra, and the modified Moshers method.

Ergosta-4,6,8(14),22-tetraen-3-one from Vietnamese Xylaria sp. possessing inhibitory activity of nitric oxide production.

From the methanolic extract of Xylaria sp. collected in Vietnam, a fluorescent constituent, ergosta-4,6,8(14),22-tetraen-3-one (1) was isolated and elucidated by the combination of 2D NMR, high resolution MS, IR and UV spectroscopy. Its inhibitory activity of nitric oxide production in RAW 264.7 cells stimulated by lipopolysaccharide was examined and showed a potential activity with the IC50 value of 28.96 µM.From the methanolic extract of Xylaria sp. collected in Vietnam, a fluorescent constituent, ergosta-4,6,8(14),22-tetraen-3-one (1) was isolated and elucidated by the combination of 2D NMR, high resolution MS, IR and UV spectroscopy. Its inhibitory activity of nitric oxide production in RAW 264.7 cells stimulated by lipopolysaccharide was examined and showed a potential activity with the IC(50) value of 28.96 microM.

Isolation, synthesis and biological activity of grifolic acid derivatives from the inedible mushroom Albatrellus dispansus

Grifolin, grifolic acid, grifolic acid methyl ester and a new compound grifolinol were isolated from methanolic extract of the inedible mushroom Albatrellus dispansus (Scutigeraceae). Their structures were established by a combination of 2D NMR, MS spectrum and chemical reaction. In addition, (+)- and (-)-daurichromenic acids were obtained by cyclization of grifolic acid. The inhibitory activity of TNF-a, anti HIV and antimicrobial activity of grifolic acid derivatives were examined.

Thelephantins A, B and C: three benzoyl p-terphenyl derivatives from the inedible mushroom Thelephora aurantiotincta.

Three benzoyl p-terphenyl derivatives named thelephantins A, B and C were isolated from the ethyl acetate extract of fruit bodies of the Thelephoraceous Basidiomycete Thelephora aurantiotincta. Their structures were elucidated by analysis of high-resolution 2D NMR, MS, IR and UV spectra.

Chemical constituents of the Vietnamese inedible mushroom Xylaria intracolorata

Investigation of the methanolic extract of Vietnamese inedible Xylariaceous mushroom Xylaria intracolorata resulted in the isolation of two new compounds named coloratin A [3,5-dimethoxy-2-(6-oxo-5-pentyl-6H-pyran-3-carbonyl)-benzoic acid] (1) and coloratin B (2-carbomethoxyl-3,5-dimethoxybenzoic acid) (2). Their structures were elucidated by 2D-NMR, MS, IR, and UV spectroscopy. Coloratin A (1) showed strong antimicrobial activity.

Main constituents from the seeds of Vietnamese Cnidium monnieri and cytotoxic activity

From the ethyl acetate extract of the seeds of Vietnamese Cnidium monnieri L., three coumarins, osthole (1), xanthotoxin (2), imperatorin (3) and a sterol, daucosterol (4) have been purified. Their structures were elucidated by spectroscopic analysis. Furthermore, 8-(3-hidroxy-3-methylbutyl)-7-methoxycoumarin (5) was synthesised from osthole (1) with a good yield (80%). In addition, compound 1 and its synthesis product (5) show moderate and non-selective cytotoxic activities against four cancer cells, KB (a human epidermal carcinoma), MCF7 (human breast carcinoma), SK-LU-1 (human lung carcinoma) and HepG2 (hepatocellular carcinoma).

Curtisians E-H: four p-terphenyl derivatives from the inedible mushroom Paxillus curtisii.

Four p-terphenyl derivatives named curtisians E-H (1-4) were isolated from the methanolic extract of fruit bodies of the Basidiomycete Paxillus curtisii by a combination of Sephadex LH-20, silica gel column chromatography and preparative reversed phase HPLC. The relative stereochemistries of the curtisians were elucidated by 2D NMR, MS, IR and UV spectroscopy with the absolute configurations at C(3a-3d) of the side chains being established as S by GC-MS on a chiral column previously used for separation of authentic standards.

Chemical constituents of the Vietnamese liverwort Porella densifolia.

From the ether extract of Porella densifolia, the first liverwort collected and chemically investigated in Vietnam, a kaurane diterpenoid, ent-kauren-15-one (1) and two sesquiterpene norpinguisone (2) and norpinguisone methyl ester (3) have been purified. Their structures were elucidated by spectroscopic analysis. In addition, an X-ray crystal structure of norpinguisone was obtained, allowing to determine its stereochemistry. Furthermore, the inhibitory activity of nitric oxide (NO) production in RAW 264.7 cells stimulated by lipopolysaccharide (LPS) of compounds 1-3 was examined with their IC(50) values of 69.4, 45.5 and 1.68 microM, respectively.