Biomedical subjects
J W ApSimon
Publications and source records attributed to J W ApSimon.
NMR structural studies of fumonisin B1 and related compounds from Fusarium moniliforme.
Fumonisin B1 (FB1) is the primary mycotoxin produced by Fusarium moniliforme and appears to be responsible for the varied toxigenic effects associated with ingestion of this mold, particularly that of the inhibition of sphingolipid biosynthesis. Understanding the structure and biosynthesis of fumonisins is a key factor in determining structure/activity relationships. To this end, Nuclear Magnetic Resonance (NMR) methods have been used to identify various derivatives of FB1, both naturally occurring and synthetic. With accurate chemical shift assignments, NMR may be used to determine the level of impurities in toxicological grade FB1 preparations. Specifically enriched FB1 was prepared from F. moniliforme cultures using 13C-enriched acetate as well as several 13C-enriched amino acids. 13C NMR analysis indicates that the biosynthesis of fumonisins involves the addition of methionine-derived methyl functions, glutamate-derived tricarballylic ester functions and alanine to an 18 carbon hydrocarbon backbone that is likely polyketide in origin. With the goal of obtaining a crystalline compound for the determination of absolute configuration, several derivatives of FB1 have been prepared, and NMR analysis used to determine the relative and absolute configuration of the 10 stereocenters present in this molecule.
The molluscicidal activity of Phytolacca dodecandra. I. Location of the activating esterase.
A number of methods have been used to extract molluscicidal saponins from the dried berries of Phytolacca dodecandra. The potency of the extract has been determined to depend on the release of an enzyme found only in the seed and breaking the seed is critical to the extraction process. The enzyme is inactivated by heat of alcohol. The highest potency extract is made from a cold water extraction of finely ground dried berries.
Variations in the levels of asterone and asterogenol, two steroids from the saponins of the starfish, Asterias vulgaris (Verrill).
The levels of two steroids, asterone 1 and asterogenol 4, obtained by hydrolysis of the crude asterosaponin mixture from the starfish Asterias vulgaris, were highest in winter and spring, then the steroid levels fell to their annual minima in July, after the spawning period. Levels also varied geographically, but the ratio of these steroids remained approximately constant.
Seasonal and geographic variations of the sterols from the starfish Asterias vulgaris (Verrill).
The levels of the major sterols of the starfish Asterias vulgaris collected at one location in Nova Scotia varied considerably from month to month. After spawning in June the levels of the sterols in the starfish were very low, but a rapid assimilation of dietary sterols allowed the total sterol level to increase approximately two-hundred-fold to the annual maximum in July. The levels of a few minor sterols were unaffected by the spawning process, and during this period they emerged as the major components of the sterol mixture. The sterol mixtures from samples collected at different locations were compared.
Quantification of a saponin steroid from the starfish Asterias vulgaris.
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Chromous chloride reduction. 8. Reaction of some derivatives and degradation products of heptachlor with chromous chloride-ethylenediamine complex and nuclear magnetic resonance and mass spectra of the products.
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