Nguyen Thi Dieu Thuan

Two new simple iridoids from the ant-plant Myrmecodia tuberosa and their antimicrobial effects

Abstract Six iridoid derivatives (1–6), including two new compounds myrmecodoides A and B (1 and 2), were isolated from the ant-plant Myrmecodia tuberosa. Their structures were determined on the basis of spectroscopic data (1H and 13C NMR, HSQC, HMBC, 1H-1H COSY, NOESY and HR-ESI-MS) and by comparison with the literature values. Among isolates, 3 and 4 exhibit weak antibacterial effect against Staphylococcus aureus subsp. aureus with MIC value of 100.0 μg/mL.

Anti-inflammatory tirucallane saponins from Paramignya scandens.

Five new tirucallane saponins, paramignyosides A-E (1-5), were isolated from the water fraction of the Paramignya scandens stem and leaves. Their structures were elucidated on the basis of spectroscopic evidence including high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) and one dimensional (1D)- and 2D-NMR. The effects of isolated compounds on pro-inflammatory cytokines were evaluated by measuring the production of interleukin (IL)-12 p40, IL-6, and tumor necrosis factor-α (TNF-α) in lipopolysaccharide (LPS)-stimulated bone marrow-derived dendritic cells (BMDCs). Paramignyoside C (3) exhibited selective and potent inhibitory effect (IC50=5.03±0.19 µM) on the production of IL-12 p40 comparable to that of the positive control, SB203580 (IC50=5.00±0.16 µM). Further studies are required to confirm efficacy in vivo and the mechanism of anti-inflammatory effects.

Bio-activities of the methanol extracts from some species belonging to the genus Polygonum in Lam Dong province

The methanol extracts from the aerial parts of eight species ( Polygonum odoratum Lour., P. pesicaria L., P. chinensis L., P. perfoliatum L., P. alatum Buch.-Ham. ex D. Don, P. strigosum R. Br., P. orientale L., P. hydropiper L.) collected in Lam Dong province were submitted to bio-tests in order to evaluate the antibacterial, antioxidant and cytotoxic effects. All of these extracts had antimicrobial activities, especially P. strigosum R. Br. could resist to E. coli, S. aureus , F. oxysporum , A. niger and S. cerevisiae ; P. orientale L. could resist to S. aureus, B. subtillis , F. oxysporum and A. niger ; P. hydropiper could resist E. coli , S. aureus, B. subtillis , F. oxysporum , A. niger and S. cerevisiae . As far as DPPH test, the MeOH extracts from P. chinensis L ., P. perfoliatum L . and P. alatum Buch.-Ham. ex D. Don were found to be the most active extracts. The MeOH extracts from these eight species had antioxydant and antimicrobial activities, therefore they had been used to cure the skin desease in the traditional medicine.

Flavonoids isolated from Dipterocarpus obtusifolius

Five flavonoids including tiliroside ( 1 ), kaempferol 3- O -(2¢¢,6¢¢-di- O -( E )- p -coumaroyl- β -D-glucopyranoside) ( 2 ), myricetin ( 3 ), myricitrin ( 4 ), and myricetin 3- O - α- arabinofuranoside ( 5 ) have been isolated and identified from the leaves of Dipterocarpus obtusifolius . Their chemical structures were elucidated by spectroscopic methods including NMR and MS, and by comparison with the literature data. All these compounds were isolated from this plant for the first time.

Iridoid constituents from the ant plant Hydnophytum formicarum

Using various chromatographic methods, four iridoids namely asperulosidic acid ( 1 ), deacetylasperulosidic acid ( 2 ), 6α-hydroxygeniposide ( 3 ), and 10-hydroxyloganin ( 4 ), were isolated from the methanol extract of the ant plant Hydnophytum formicarum . The structural elucidation was done using 1D and 2D-NMR experiments and comparison of the NMR data with reported values. This is the first report of these compounds from H. formicarum .

Secondary metabolites from Dipterocarpus obtusifolius Teijsm. Ex Miq

Six known compounds daphneresinol ( 1 ), (+)-neo-olivil ( 2 ), methyl gallate ( 3 ), bergenin ( 4 ), asiatic acid ( 5 ) and blumenol A ( 6 ) were obtained from the organic extract of the leaves of Dipterocarpus obtusifolius Teijsm. Ex Miq. by various chromatographic techniques. Structural elucidation of the metabolites was carried out by analysis of their spectroscopic data and by comparison with those reported in the literature. C ompounds 1 - 4 and 6 were isolated from this plant for the first time.

Phenolic compounds from the seeds of Scaphium macropodum (MIQ.) Beumée

Five known compounds 6,7,9α-trihydroxy-3,8,11α-trimethylcyclohexo-[d,e]-coumarin ( 1 ), mansonone H ( 2 ), ( R )-lasiodiplodin ( 3 ), trans-p -coumaric acid ( 4 ) and 3,4-dihydroxybenzaldehyde ( 5 ) were obtained from the organic extract of the seeds of Scaphium macropodum (Miq.) Beumee by various chromatographic techniques. Structural elucidation of the metabolites was carried out by analysis of their spectroscopic data and by comparison with those reported in the literature. All the c ompounds were isolated from this plant for the first time. Keywords. Scaphium macropodum , Sterculiaceae, phenolic compound.

Seasonal effects on the 10-deacetylbaccatin III and 19-hydroxybaccatin III contents of the needles of Taxus wallichiana Zucc. in Lam Dong province

In Vietnam, there are two Taxus species ( Taxus chinensis (Pilg.) Rehd. in Northern provinces and Taxus wallichiana Zucc. in Western Highland). Previous examinations show that content of taxoid compounds in the needles of T. chinensis is lower than in the needles of T. wallichiana , so that materials from T. chinensis don’t meet the requirements of pharmaceutical industry. Taxus wallichiana Zucc. (Taxaceae) only distributes in Lamdong province of Vietnam. Its needles were collected monthly from May 2005 to April 2006. The humidity of fresh needles was variety from 59 to 71 percent depending on seasonal conditions. Uniformly dried samples of Taxus wallichiana Zucc . were extracted and analyzed for their contents of two taxanes, namely 10-deacetylbaccatin III (DAB) and 19-hydroxybaccatin III (HB) using high pressure liquid chromatography instrument with the standard compounds. The content of DAB in the dried needles gradually increases according to the harvest time from January to July and sequentially decreases to the end of year. The maximum content of DAB is 0.037% in the dried needles collected in June or July. The lowest level was reached in February – March (0.012%). Similarity, the highest content of HB is 0.032% based on dried needles collected in June. The minimum level of HB is 0.014% on needles collected in January. Data obtained from a seasonal study showed that the best time to harvest of the yew clippings for the production of these two taxanes is approximately one month from the start of flushing (June to July). At that time the clippings have reached reasonable size to provide high quality biomass.

Bio-activities of the methanol extracts from some species belonging to the family Asteraceae in Lam Dong province

The methanol extracts from 8 species belonging to the family Asteraceae in Lam Dong province were evaluated through antibacterial, DPPH radical scavenging and cytotoxic tests. The MeOH extracts from Ageratum conyzoides L. (whole plant), Bidens pilosa L. (whole plant) and Chromolaena odorata (L.) R. M. King & H. Rob. (aerial parts) showed the highest capacities in Esherichia coli and Staphylococus aureus tests. In the DPPH radical scavenging test, the MeOH extracts from Sonchus oleraceus L. (whole plant), Pluchea indica (L.) Less (aerial parts) and Xanthium strumarium L. (fruits) were the most active. The MeOH extracts from Elephantopus mollis H. B. K. (whole plant), Chromolaena odorata (L.) R. M. King & H. Rob. (aerial parts) and Xanthium strumarium L. (fruits) showed cytotoxic activities.