References: Lecithin
Clin Chem. 1989 May;35(5):800-3.
Phospholipid surface tension: the diagnostic utility of amniotic fluid and its lipid extract, an analysis of the value of precipitation with cold acetone.
Ruiz Budria J, Abbad Bara JM, Fabre Gonzalez E, Higueras Sanz MT, Serrano Ostariz JL.
Department of Organic Chemistry, University of Zaragoza, Spain.
In prevention of the respiratory distress syndrome (RDS), measurements of surface tension values (a biophysical property) of amniotic-fluid samples are correlated with their lecithin/sphingomyelin (L/S) ratios (a biochemical property). According to some authors, precipitation of phospholipid with cold acetone is essential for determining the L/S ratio, because it separates surfactant and nonsurfactant phospholipidic fractions. Here we report the first study of the ability of three amniotic-fluid components to decrease surface tension: The complete lipid extract (without precipitation), and the fractions precipitated and (or) remaining soluble after addition of cold acetone. Addition of increasing aliquots of lipid extracts to these three samples showed that: (a) measurement of surface tension rapidly and reliably indicates fetal lung maturity, and (b) both precipitated and soluble phospholipid fractions decrease surface tension similarly, making it unlikely that the precipitation step in fact separates surfactant and nonsurfactant material.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2720973&dopt=Abstract lecithin
J Pharm Biomed Anal. 1993 Jun;11(6):505-11.
Deactivated hydrocarbonaceous silica and immobilized artificial membrane stationary phases in high-performance liquid chromatographic determination of hydrophobicities of organic bases: relationship to log P and CLOGP.
Kaliszan R, Kaliszan A, Wainer IW.
McGill University, Department of Oncology, Montreal General Hospital, Quebec, Canada.
Retention parameters for a series of 29 organic base drugs (including 17 phenothiazine derivatives) were measured by reversed-phase high-performance liquid chromatography (HPLC) employing new columns of distinctive partition properties. One column was a deactivated alkyl-bonded silica and two others were packed with lecithin-bonded propylamino-silica, i.e. the immobilized artificial membrane (IAM) columns; one of the IAM stationary phases had the unreacted propylamine moieties additionally end-capped with methylglycolate. The highly deactivated hydrocarbonaceous silica column showed regular rectilinear relationships between logarithms of chromatographic capacity factors and the content of organic modifier in aqueous eluent; it is suitable for generating a chromatographic scale of hydrophobicity. Such a scale (hydrocarbonaceous) is different from that provided by measurement of partitioning of solutes between n-octanol and water (alkanol log P scale). The relative hydrophobicity parameters determined by HPLC on the IAM columns were different from both log P scale and from the hydrocarbonaceous chromatographic hydrophobicity scale. The hydrophobicity parameter, CLOGP, theoretically calculated by the fragmental methods, correlated better than log P with chromatographic hydrophobicity parameters. It has been postulated that each hydrophobicity measuring system reveals some specific aspects of the hydrophobicity phenomenon and that the nature of hydrophobic binding sites on receptors and plasma proteins may require different hydrophobicity models than drug permeation through biological membranes. By means of HPLC, diverse
agemed.es
Pseudoternary phase diagrams have been constructed to evaluate the phase behavior of systems containing water/lecithin/polysorbate 80/isopropyl myristate at different polysorbate 80:lecithin weight ratios (K(m)). Oil-in-water microemulsion regions were accurately determined and the influence of the K(m) on the area of existence of such disperse systems was also examined. Viscosity studies as well as particle size analysis by dynamic light scattering were carried out on oil-water microemulsions, and the influence of the oil phase content, the total amount of surfactants and K(m) on the rheological behavior, viscosity, and droplet size of such disperse systems was evaluated. All systems studied showed a water-rich isotrope region (oil-in-water microemulsion area), that was seen to be highly dependent upon the surfactant/cosurfactant weight ratio. Most of the microemulsions analyzed showed a non-Newtonian rheological behavior and both, droplet size, and viscosity of the disperse systems, were found to be much more influenced by the total content of oil phase and surfactants present in the microemulsion than by the K(m). The selected system underwent both stability and in vivo acute toxicity studies, and seemed to be highly stable, even at extreme conditions, and very low toxic according to the results obtained. Copyright 2003 Wiley-Liss, Inc. and the American Pharmacists Association
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12820147&dopt=Abstract lecithin
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