High-performance liquid chromatographic method for the determination of cefpodoxime levels in plasma and sinus mucosa

A selective HPLC method is described for the determination of cefpodoxime levels in plasma and sinus mucosa. Sample preparation included solid-phase extraction with a C₈ cartridge. Cefpodoxime and cefaclor (internal standard) were eluted with methanol and analyzed on an optimised system consisting of a C₁₈ stationary phase and a ternary mobile phase (0.05 M acetate buffer pH 3.8—methanol—acetonitrile, 87:10:3, v/v) monitored at 235 nm. Linearity and both between- and within-day reproducibility were assessed for plasma and sinus mucosa samples. Inter-assay coefficients of variation were lower than 13.6% (n = 10) for plasma (0.2 μg/ml) and lower than 12.4% (n = 5) for sinus mucosa (0.25 μg/g). The quantification limit was 0.05 μg/ml for plasma and 0.13 μg/g for tissue. The method was used to study the diffusion of cefpodoxime in sinus mucosa.     

Crystalline conformation of homo- and regular heteroglucan chains

Crystalline polysaccharides with 1 → 3−β and 1 → 4−β glycosidic linkages are the most prevalent ones in nature. An interpretation of recent X-ray data on 1 → 3−α glucan shows that it has a ribbon-like crystalline conformation similar to cellulose. Comparison of the crystalline conformation of the four principal homoglucans shows that they fall either in the ‘ribbon-like’ or ‘large amplitude’ helix class. Heteroglucans with a regular sequence of glucosidic linkages show characteristics of the ‘extended conformation’ rather than the ‘coiled conformation’ even when there is 50% of a linkage which in a homoglucan leads to a large amplitude helix. It is concluded that X-ray diffraction analysis fully establishes the hypothesis that the glycosidic linkage type is the determinant of polysaccharide conformation. In this respect, polysaccharides are more like synthetic polymers than proteins or nucleotides; in the latter, it is variation in the substituents which are responsible for the conformational diversity.     

Contribution on the content and nature of the phycocolloid from Kallymenia reniformis (Cryptonemiales,Rhodophyta)

The red alga Kallymenia reniformis (Rhodophyta, Cryptonemiales), collected on the west coast of Brittany, contained 13% ash, 5.6% crude protein and 38.7% soluble carbohydrate (on percent dry wt). The phycocolloid extract (38 % dried wt) was investigated using chemical and spectroscopic (IR and ¹³C NMR) methods. Preliminary results show that this polysaccharide belongs to the lambda-carrageenan family.     

Influence of day-night and tidal cycles on phenol content and antioxidant capacity in three temperate intertidal brown seaweeds

The daily variations of phenol contents and antioxidant capacities were surveyed in a 32-h field experiment in three temperate brown seaweeds belonging to Fucales - Pelvetia canaliculata, Ascophyllum nodosum and Bifurcaria bifurcata - living at different intertidal levels — high-, mid- and low-tide level, respectively. Phenolic compounds of brown seaweeds are secondary metabolites involved in many different protection mechanisms, as for example against grazer and pathogen attack as well as UV damage. This study was thus aimed at understanding the influence of both day/night and tidal cycles on the brown seaweed phenol pool with respect to their bathymetric level on the shore. These cycles affect the quantity and quality of light received by intertidal seaweeds (protection via the water layer during immersion), and the photoprotective role of phlorotannins was thus evaluated. Phenol levels and antioxidant capacities were monitored every hour during a tidal cycle and a half at the equinox spring tide, in March 2003. The three species contained rather high phenol levels, i.e. about 3, 6 and 4% DW in P. canaliculata, A. nodosum and B. bifurcata, respectively. Antioxidant capacities globally paralleled phenol contents in the three species under study. Moreover, the measured antioxidant capacities and the phenol contents of the extracts were significantly and positively correlated in the three species. Significant effect of neither cycles nor their interaction was observed in any species despite a trend to follow day/night alternation for P. canaliculata, and emersion/immersion cycle for A. nodosum. No trend was observed for the third species. However, significant correlations between phenol levels of P. canaliculata and A. nodosum and measured air-temperature were found. Our results suggested an effect of aerial, aquatic and both conditions on the phenolic pool of P. canaliculata, B. bifurcata and A. nodosum, respectively, and a fast evolution of the phenolic pool on a day time scale.     

A liquid chromatography assay for a quantification of doripenem, ertapenem, imipenem, meropenem concentrations in human plasma: application to a clinical pharmacokinetic study

A simple chromatographic assay based on ultra high performance liquid chromatography with ultraviolet detection at 295 nm is proposed to determinate simultaneously human plasma concentrations of imipenem, doripenem, meropenem and ertapenem. After deproteinization by acetonitrile, carbapenems are separated on a PentaFluoroPhenyl column with a binary gradient elution. This method is specific, accurate, precise (the intra-day and inter-day imprecision and inaccuracy are lower than 15%), sensitive (the limit of quantitation is equal to 0.50 mg/L for imipenem, doripenem, ertapenem, meropenem) and not time consuming (run time=7 min). An application of this method to measure ertapenem plasma concentrations in burn patients is presented.     

Chemical characteristics of a polysaccharide from Porphyra capensis (Rhodophyta)

The structure of a polysaccharide from the red seaweed, Porphyra capensis, growing along the coast of Namibia and South Africa was investigated. Algae growing at different sites and collected at different times gave a polysaccharide extract with similar chemical components. FTIR and NMR spectral analysis showed that the polysaccharide from P. capensis had a typical porphyran structure. It has the linear backbone of alternating 3-linked beta-D-galactose and 4-linked alpha-L-galactose-6-sulfate or 3,6-anhydro-alpha-L-galactose units. The ratio of alpha-L-galactose-6-sulfate and the 3,6-anhydrogalactose is 1.2:1, as reflected by a 1H NMR spectrum. A high degree of methylation occurred at the C-6 position of the D-galactose units. The degree of methylation was 0.64 for the D-galactose residues.     

Comparative proteomic analysis of cisplatin sensitive IGROV1 ovarian carcinoma cell line and its resistant counterpart IGROV1-R10

Ovarian cancer is one of the leading causes of mortality due to gynaecological cancer. Despite a good response to surgery and initial chemotherapy essentially based on cisplatin (cis-diamino-dichloro-platinum(II) (CDDP)) compounds, late tumour detection and frequent recurrences with chemoresistance acquisition are responsible for poor prognosis. Several mechanisms have been implicated in CDDP resistance but they are not sufficient to exhaustively explain this resistance emergence. We applied a proteomic approach based on 2-DE coupled with MS to identify proteins associated with the chemoresistance process. We first established a proteomic pattern of the CDDP sensitive ovarian cell line IGROV1 using MALDI-TOF-MS and PMF. We then compared this 2-D pattern with that of the CDDP-resistant counterpart IGROV1-R10. Among the 40 proteins identified, cytokeratins 8 and 18 and aldehyde dehydrogenase 1 were overexpressed in IGROV1-R10, whereas annexin IV was down-regulated. These observations have been confirmed by Western blotting. The characterization of such variations could lead to the development of new protein markers or to the establishment of new therapeutic strategies. Moreover, the identification of proteins involved in CDDP resistance in ovarian tumours would be useful in completing our understanding on this complex mechanism.