Structural characterization and cytotoxic properties of a 4-O-methylglucuronoxylan from castanea sativa. 2. Evidence of a structure-activity relationship

Xylans were purified from delignified holocellulose alkaline extracts of Castanea sativa (Spanish chestnut) and Argania spinosa (Argan tree) and their structures analyzed by means of GC of their per-trimethylsilylated methylglycoside derivatives and (1)H NMR spectroscopy. The structures deduced were characteristic of a 4-O-methylglucuronoxylan (MGX) and a homoxylan (HX), respectively, with degrees of polymerization ranging from 182 to 360. In the case of MGX, the regular or random distribution of 4-O-methylglucuronic acid along the xylosyl backbone--determined by MALDI mass spectrometry after autohydrolysis of the polysaccharide--varied and depended both on the botanical source from which they were extracted and on the xylan extraction procedure. The MGX also inhibited in different ways the proliferation as well as the migration and invasion capability of A431 human epidermoid carcinoma cells. These biological properties could be correlated with structural features including values of the degree of polymerization, 4-O-MeGlcA to xylose ratios, and distribution of 4-O-MeGlcA along the xylosyl backbone, giving evidence of a defined structure-activity relationship.

Solvent-controlled regioselective protection of 5'-O-protected thymidine

This paper describes an efficient procedure for selective 3'-O- or 3-N-protection of 5'-O-tert-butyldimethylsilylthymidine, depending on the use of aprotic polar solvents with low or high dielectric constant, respectively. These syntheses were activated by either ultrasound or microwaves. Several alkyl bromides offer a convenient route to prepare 3'-O- or 3-N-protected and functionalized thymidine derivatives.

Synthesis and cellular uptake of superparamagnetic dextran-nanoparticles with porphyrinic motifs grafted by esterification

This paper describes new superparamagnetic nanoparticles bearing dextran-grafted porphyrins with effective cellular uptake properties. They average 110 nm in diameter and are composed of a 5 nm iron oxide core coated with protoporphyrin-grafted dextrans. These particles show good magnetic properties, are avidly incorporated into cultured cancer cell lines, and thus present a great potential for cellular imaging and photodynamic therapy applications.

Synthesis and antiviral evaluation of AZT analogues with A spacer arm between glucidic and base moieties. Part II

This article describes the synthesis of a series of AZT analogues bearing an acyclic chain between the sugar and the base moieties is described. These new compounds were readily obtained using microwave irradiation. The compounds were characterized by (1)H NMR and IR spectroscopy. Antiviral (HIV-1) properties of these compounds were examined.

Bioactive capsular polysaccharide from the thermophilic cyanophyte/cyanobacterium Mastigocladus laminosus - cytotoxic properties

The capsular polysaccharide produced by the thermophilic blue green alga/cyanobacterium Mastigocladus laminosus was tested for its cytotoxic activity against the A431 human epidermoid carcinoma cell line. This polysaccharide inhibited the proliferation of A431 cells in a dose-dependent manner with an IC (50) value of 50 microg mL (-1). In addition, this polysaccharide strongly inhibited A431 cell migration and invasion. Preliminary experiments showing that secretion of metalloproteinases MMP2 and MMP9 by A431 tumour cells was inhibited by this polysaccharide suggest that this mechanism of action could play a role in its anti-migration and anti-invasive properties. Acid hydrolysis of the polysaccharide produced specific oligosaccharides which conserved - at similar concentrations - their cytotoxic, anti-migration and anti-invasion properties; in this case, the mechanism of action was nevertheless uncorrelated to the decrease of metalloproteinase expression.

Structural characterization and cytotoxic properties of a 4-O-methylglucuronoxylan from Castanea sativa

A glucuronoxylan was purified from a delignified holocellulose alkaline extract of Castanea sativa (Spanish chestnut) and its structure analyzed by means of FT-IR, GC of the per-trimethylsilylated methylglycoside derivatives, and 1H and 13C NMR spectroscopy. The results supported a structure based on a linear polymer of xylopyranose units linked with beta(1-->4) bonds in which, on average, one out of every six units is substituted at C-2 by a 4-O-methylglucuronic acid unit; this structure is typical of a hardwood acidic 4-O-methylglucuronoxylan (MGX) with an estimated degree of polymerization of 200. The MGX from C. sativa inhibited the proliferation of A431 human epidermoid carcinoma cells with an IC50 value of 50 microM. In addition, this xylan inhibited A431 cell migration and invasion. Preliminary experiments showing that secretion of metalloproteinases MMP2 and MMP9 by A431 tumor cells was inhibited by the purified C. sativa MGX strongly suggest that this mechanism of action may play a role in its antimigration and anti-invasive properties.

Glycosyl bis-porphyrin conjugates: Synthesis and potential application in PDT

Syntheses of new glycosylated neutral and cationic porphyrin dimers linked at the meso-position via a flexible hydrocarbon chain are described. A detailed 1H and 13C NMR study allows their complete structural elucidation. The UV-visible, fluorescence and MALDI mass spectra are also presented. Photocytotoxicities of these compounds against K562 leukaemia cell line are compared to those of Photofrin II.

Effect of degree of substitution on the mechanical and thermomechanical properties of lauroyl cellulose ester films

Cellulose-based plastic films were prepared in homogeneous media with a range of lauroyl fatty acid attachments by ester formation, expressed as the degree of substitution (DS). The esters were cast to form films and their mechanical properties studied. This study showed a surprising relationship between DS and elastic modulus as well as DS and tensile strength, where a peak was observed at DS 2.4. The unexpected variation of static elastic modulus (E) was confirmed by dynamic mechanical analysis (DMA) and this trend was also observed for glass transition temperature (Tg). These results are discussed in relation to sample cohesion.

Synthesis and photocytotoxic activity of new chlorin–polyamine conjugates

This paper reports the synthesis of new chlorin-polyamine conjugates designed to improve the targeting of cancer cells. Photocytotoxic activity of these photosensitizers was tested against human chronic myelogenous leukemia cells (K562) and compared to the effects of Photofrin II and chlorin e6.

Polyamine conjugates of meso-tritolylporphyrin and protoporphyrin IX: Potential agents for photodynamic therapy of cancers

An efficient five-step synthesis method was developed to obtain tritolylporphyrin and protoporphyrin IX polyamine conjugates. These compounds were composed of either one polyamine unit (spermidine or spermine) covalently tethered to monocarboxyphenyl tritolylporphyrin or two molecules of polyamines borne by protoporphyrin IX. In each compound, an aliphatic spacer arm is linked to the N(4) polyamine position. Photocytotoxicity of these new compounds was evaluated against K562 human chronic myelogenous leukemia cells and compared to Photofrin II; protoporphyrin IX polyamine conjugates exhibited much stronger photocytocicity than Photofrin II and were shown to readily induce necrosis in treated cells.

New photoantimicrobial films composed of porphyrinated lipophilic cellulose esters

Porphyrinated cellulose laurate esters have been prepared in homogeneous DMA/LiCl medium by "one-pot, two-step" reactions starting from cellulose, protoporphyrin IX, and lauric acid and using a TsCl/Pyridine system. The plastic films obtained after casting were shown to display photobactericidal activity against Gram positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. This new photobactericidal polymer has potential for industrial, medical, or household applications.

Study of the chemical interaction between barks and heavy metal cations in the sorption process

The chemical mechanism displayed in the sorption of heavy metal cations on barks was discussed through a modelling study of adsorption in relation to the nature of the ligand borne by the chemical components of the bark sorbent. The adsorption isotherms of five heavy metal cations (Cr3 +, Cu2 +, Ni2 +, Pb2 +, Zn2+) on five species of barks (Sweet chestnut, Oak, Douglas fir, Norway spruce, Scots pine species) were studied. The experimental data fitted well the Langmuir model, which allowed the expression of the mathematical parameters (qmax, maximum binding capacity; b, affinity). The qmax values increased conversely to the b values. The correlation of these mathematical values (qmax and b) with the analysis of the chemical composition of barks led us to note that Cu2 + interacts preferentially with phenolic groups present in lignins and tannins and, opposite in, Pb2 + with the carboxylic acid groups in polysaccharides. These observations were explained (i) quantitatively by the amount of different types of sites and (ii) qualitatively, by the physicochemical characteristics of cations, the nature and the tridimensional structure of adsorption sites. Finally, the results allowed to define the nature of the chemical interaction (monodentate or multidentate complex) between each specified chemical component of barks and each kind of heavy metal cations.