VEGETABLE PURGATIVES CONTAINING ANTHRACENE DERIVATIVES
In Part I of this series of papers1 reference was made to a preliminary test on an extract of Senna pod which was found to contain only about 5 per cent. of its theoretical activity. Biological and chemical tests have since been carried out on a number of galenical preparations of senna pod and the results have confirmed that only a small proportion of the activity of the pod is present in these concentrated preparations. The ultimate aim of the work described in this paper has been to devise a method of preparing an extract representing the full activity of the pod from which it was made, and as a result, it has been possible to set out the principles underlying efficient extraction and concentration processes.
VEGETABLE PURGATIVES CONTAINING ANTHRACENE DERIVATIVES
A new kind of anthraquinone compound has been isolated from cascara bark (Rhamnus purshiana). Unlike the normal glycosides it cannot be hydrolysed by heating in acid solution, but on heating in acidified ferric chloride solution aloe-emodin and a second anthraquinone, possibly chrysophanol, are produced. Some of the physical properties are described including the ultra-violet light absorption curve which shows peaks at 268, 296 and 325 mμ. The relationship of this compound to casanthranol and to the chemical assay and biological activity of cascara is discussed.
The peculiar thermo-structural behavior of the anionic lipid DMPG.
Aqueous dispersions of the anionic phospholipid dimyristoyl phosphatidylglycerol (DMPG), around 100 mM ionic strength, are known to exhibit a thermal behavior similar to that of the largely studied lipid dimyristoyl phosphatidylcholine (DMPC), which undergoes a gel to liquid crystalline phase transition at 23 degrees C, well characterized by differential scanning calorimetry (DSC), and other methods. However, at low ionic strength, DMPG has been shown to present a large gel-fluid transition region, ranging from 18 to 35 degrees C. This intermediate phase is optically transparent and characterized by a continuous change in membrane packing. Structural properties of the DMPG gel-fluid transition region will be discussed, based on results obtained by several techniques: electron spin resonance (ESR) of spin labels at the membrane surface and intercalated at different depths in the bilayer; light scattering; DSC; small angle X-ray scattering (SAXS); and fluorescence spectroscopy of probes in the bilayer.