A new derivative of glucose and 2-C-methyl-D-erythritol from Ferula sinaica

Non-ephedrine constituents from the herbaceous stems of Ephedra sinica

Three new flavonoids, ephedroside A (1), ephedroside B (2), ephedroside C (3), together with fifty-four known compounds 4-57 were isolated from the EtOH extract of the herbaceous stems of Ephedra sinica. The structures of these compounds were elucidated by spectroscopic techniques, as well as by comparison with literature data. Thirty-eight of these compounds were isolated from the genus Ephedra for the first time. The antimicrobial activities of eight compounds were tested by measuring the minimum inhibitory concentrations (MIC) against bacteria (both Gram positive and Gram negative) and fungi, and were found to be in the range of 0.105-0.926 mM. Among them, compound 2 showed the best antimicrobial activity against Pseudomonas aeruginosa with MIC value of 0.105 mM.

Wound healing activity and phytochemical screening of purified fractions of Sempervivum tectorum L. leaves on HCT 116

INTRODUCTION

Sempervivum tectorum L. (Crassulaceae), is a succulent perennial plant widespread in Mediterranean countries and commonly used in traditional medicine for ear inflammation, ulcers and skin rashes as a refrigerant and astringent.

OBJECTIVE

To demonstrate the therapeutic effects of the plant, various fractions were purified and characterised. The potential wound healing activity, proliferation rate and intracellular signalling cascades were investigated by using human epithelial colorectal carcinoma (HCT 116) cells.

METHODOLOGY

An extraction method without organic solvents was applied for the first time. The purification was carried out by droplet counter current chromatography (DCCC) coupled with high-performance liquid chromatography (HPLC) and electrospray ionisation mass spectrometry (ESI-MS) data. By nuclear magnetic resonance (NMR) [¹ H, ¹³ C and two-dimensional (2D) experiments] pure components were identified. Wound healing and cell proliferation assays were utilised to determine the role of the isolated S. tectorum (SVT) fraction on cellular migration and proliferation. The signalling pathways elicited from the SVT fractions, were analysed by Western blot analysis.

RESULTS

In this study two rare natural components were identified, namely monosaccharide sedoheptulose and polyalcohol 2-C-methyl-D-erythritol, along with known organic acids and flavonoids. The fractions with high level of sedoheptulose enhance the proliferation and the cellular migration of epithelial HCT 116 cells. The intracellular signalling cascades elicited from the purified fractions induce the c-Src-mediated transactivation of EGFR and the activation of the STAT3 pathway which, in turn, are crucially involved in the cellular proliferation and migration.

CONCLUSIONS

Our study demonstrates the efficacy of purified fractions of S. tectorum L. in enhancing cellular proliferation and migration, suggesting their potential role as topical therapeutic treatments for wound healing.

Primary and secondary organics in the tropical Amazonian rainforest aerosols: chiral analysis of 2-methyltetraols

This work presents the application of a new method to facilitate the distinction between biologically produced (primary) and atmospherically produced (secondary) organic compounds in ambient aerosols based on their chirality. The compounds chosen for this analysis were the stereomers of 2-methyltetraols, (2R,3S)- and (2S,3R)-methylerythritol, (l- and d-form, respectively), and (2S,3S)- and (2R,3R)-methylthreitol (l- and d-form), shown previously to display some enantiomeric excesses in atmospheric aerosols, thus to have at least a partial biological origin. In this work PM10 aerosol fractions were collected in a remote tropical rainforest environment near Manaus, Brazil, between June 2008 and June 2009 and analysed. Both 2-methylerythritol and 2-methylthreitol displayed a net excess of one enantiomer (either the l- or the d-form) in 60 to 72% of these samples. These net enantiomeric excesses corresponded to compounds entirely biological but accounted for only about 5% of the total 2-methyltetrol mass in all the samples. Further analysis showed that, in addition, a large mass of the racemic fractions (equal mixtures of d- and l-forms) was also biological. Estimating the contribution of secondary reactions from the isomeric ratios measured in the samples (=ratios 2-methylthreitol over 2-methylerythritol), the mass fraction of secondary methyltetrols in these samples was estimated to a maximum of 31% and their primary fraction to a minimum of 69%. Such large primary fractions could have been expected in PM10 aerosols, largely influenced by biological emissions, and would now need to be investigated in finer aerosols. This work demonstrates the effectiveness of chiral and isomeric analyses as the first direct tool to assess the primary and secondary fractions of organic aerosols.

Four new hemiterpenoid derivatives from Taxillus chinensis

Four new hemiterpenoid derivatives, taxilluside A-D (1-4), were isolated from the branches and leaves of Taxillus chinensis (DC.) Danser. Their structures were determined on the basis of spectroscopic analysis. Of these compounds, compounds 3 and 4 showed inhibition activity on Calcium concentration in myocardial cells evaluated by measuring the changes of fluorescence signal using Laser scanning confocal microscope.

A raison d'être for two distinct pathways in the early steps of plant isoprenoid biosynthesis?

When compared to other organisms, plants are atypical with respect to isoprenoid biosynthesis: they utilize two distinct and separately compartmentalized pathways to build up isoprene units. The co-existence of these pathways in the cytosol and in plastids might permit the synthesis of many vital compounds, being essential for a sessile organism. While substrate exchange across membranes has been shown for a variety of plant species, lack of complementation of strong phenotypes, resulting from inactivation of either the cytosolic pathway (growth and development defects) or the plastidial pathway (pigment bleaching), seems to be surprising at first sight. Hundreds of isoprenoids have been analyzed to determine their biosynthetic origins. It can be concluded that in angiosperms, under standard growth conditions, C₂₀-phytyl moieties, C₃₀-triterpenes and C₄₀-carotenoids are made nearly exclusively within compartmentalized pathways, while mixed origins are widespread for other types of isoprenoid-derived molecules. It seems likely that this coexistence is essential for the interaction of plants with their environment. A major purpose of this review is to summarize such observations, especially within an ecological and functional context and with some emphasis on regulation. This latter aspect still requires more work and present conclusions are preliminary, although some general features seem to exist.

2-C-methyl-D-erythritol is a major carbohydrate in petals of Phlox subulata possibly involved in flower development

2-C-methyl-D-erythritol, a soluble carbohydrate that is not ubiquitously found in higher plants, was detected in the ethanol extract from Phlox subulata petals and isolated using HPLC. The isolated compound was identified by 1H-NMR, 13C-NMR and Cl-MS spectra. 2-C-methyl-D-erythritol was a major soluble carbohydrate in petals, leaves and stems. In petals, the concentration of 2-C-methyl-D-erythritol markedly increased during flower development and opening and was similar in concentration to glucose, a ubiquitous metabolic sugar. This suggests that 2-C-methyl-D-erythritol may contribute to flower opening in association with glucose in the P. subulata.

Prediction of 1H NMR chemical shifts using neural networks

Counterpropagation neural networks were applied to the fast prediction of 1H NMR chemical shifts of CHn groups in organic compounds. The training set consisted of 744 examples of protons that were represented by physicochemical, topological, and geometric descriptors. The selection of descriptors was performed by genetic algorithms, and the models obtained were compared to those containing all the descriptors. The best models yielded very good predictions for an independent prediction set of 259 cases (mean absolute error for whole set, 0.25 ppm; mean absolute error for 90% of cases, 0.19 ppm) and for application cases consisting of four natural products recently described. Some stereochemical effects could be correctly predicted. A useful feature of the system resides in its ability to be retrained with a specific data set of compounds if improved predictions for related structures are required.

An eudesmanolide and a carotane from Ferula sinaica

Re-examination of the chemical constituents of the leaves of Ferula sinaica afforded a new eudesmanolide and a new carotane. The structures were elucidated by spectroscopic methods.

Synthesis of 2-C-methyl-D-erythritol and 2-C-methyl-L-threitol; determination of the absolute configuration of 2-C-methyl-1,2,3,4-butanetetrol isolated

2-C-Methyl-D-erythritol (A) and 2-C-methyl-L-threitol (B) were respectively synthesized from D-glucose and D-galactose. The 2-C-methyl-1,2,3,4-butanetetrol compound (C) recently isolated from Phlox sublata L was confirmed to be A by comparing the CD and 1H-NMR spectra of its tri-O-benzoate with those of A and B.

Isoprenoid biosynthesis via the mevalonate-independent route, a novel target for antibacterial drugs?

Mevalonate was accepted as the universal precursor of all isoprenoids. This assertion was however revealed to be partially incorrect. Incorporation of 13C labeled acetate and glucose into bacterial triterpenoids of the hopane series allowed for the discovery and the partial elucidation of a novel biosynthetic pathway leading to isopentenyl diphosphate. The C5 skeleton of isoprenic units results from the condensation of (hydroxyethyl)thiamin on the carbonyl group of glyceraldehyde 3-phosphate, yielding D-1-deoxyxylulose 1-phosphate. A subsequent intramolecular rearrangement is involved in the formation of the branched isoprenic skeleton. 2C-Methyl-D-erythritol (or its mono- or diphosphate) was shown to be a putative intermediate. This pathway is widespread in bacteria including opportunistic pathogens or innocuous species related to well-known pathogens. In plants, it is involved in the formation of essential chloroplast isoprenoids (carotenoids, phytol, plastoquinone) and of probably most other plastid related isoprenoids of more restricted distribution (isoprene, mono- and diterpenoids). Therefore it potentially represents a novel target for antibacterial drugs and herbicides.