Brian Vickery

Analysis of plants for fluoroacetic acids

Abstract A paper chromatographic separation of mono-, di- and tri-fluoroacetic acids applicable to plant analysis is described. Improvements to the thioindigo m

Suppression of interfering ions in the analysis of plants to determine fluoride using the fluoride ion selective electrode

Plant ashes may contain sufficient aluminium and/or iron to interfere seriously in the determination of fluoride ions when using the fluoride ion selective electrode. In the presence of these metals the known additions method gave erroneous results, as did that involving the attempted formation of complexes with ethylenediaminetetraacetic acid, disodium salt, or 1,2-cyclohexylenedinitrilotetraacetic acid. Good recoveries of fluoride ion were obtained in the presence of aluminium, iron, magnesium or silicate, using sodium citrate as the complexing agent. The application of the citrate complex method to ashes of commercial tea, high in aluminium and iron, gave recoveries of fluoride ion of greater than 90%.

Fluoride metabolism in Dichapetalum toxicarium

Abstract The monofluoroacetate and fluoride ions are present in varying concentrations throughout Dichapetalum toxicarium (G. Don) Baill. (Dichapetalaceae). The synthesis of the monofluoroacetate ion takes place in the young leaves of the plant. This ion is stored in the small leaves adjacent to the flowers until withdrawn by the embryo seeds, in which it is converted to long-chain fluoro fatty acids. The fluoride ion is an intermediate in the synthesis of the monofluoroacetate ion and D. toxicarium has an unusual ability to withdraw fluoride from a low fluoride environment.

The synthesis and defluorination of monofluoroacetate in some Dichapetalum species

Abstract Leaves from Dichapetalum toxicarium (G. Don) Baill. (Dichapetalaceae) removed from the plant and aqueous extracts prepared from the leaves of D. heudelotii (Planch. ex Oliv.) Baill. were able to synthesize monofluoroacetate from NaF. D. pallidum (Oliv.) Engl. leaves were not able to synthesize monofluoroacetate from NaF. Aqueous extracts from both D. toxicarium and D. heudelotii containing monofluoroacetate and possibly other organo-fluorine compounds were defluorinated by a micro-organism from the air. This organism was able to defluorinate fluorocitrate but not difluoroacetate or trifluoroacetate. In D. toxicarium monofluoroacetate is present in a form which is easily leached from the leaves, and which is defluorinated if the leaves are kept under herbarium conditions. The monofluoroacetate in this species is not defluorinated if the leaves are dried at 100° and stored in sealed polythene bags.

The Acetate-Malonate Pathway

Numerous compounds classed as terpenoids or steroids are biosynthesised by the acetate-mevalonate pathway. The terms terpenoid and isoprenoid are interchangeable, isoprenoid referring to the five-carbon isoprene unit (5.1) from which all terpenoids are theoretically derived. This isoprene rule, which states that all terpenoids are multiples of the isoprene unit (i.e. C10, C15, C20, etc.), is not strictly obeyed by natural products, although most compounds classed as terpenoids can be seen to be derived from such units (Figure 5.1). Open image in new window Figure 5.1 Natural compounds following the isoprene rule.

Shikimic Acid Pathway Metabolites

Benzenoid compounds in plants are biosynthesised by two main pathways: the shikimic acid pathway and the acetate-malonate pathway (Chapter 4). In higher plants, a large number of aromatic compounds are derived from phenylalanine, tyrosine and tryptophan, end-products of the shikimic acid pathway. Some of these compounds are discussed in this chapter, others will he found in Chapters 7 and 9.

Compounds with a Mixed Biogenesis

Aromatic compounds in plants are generally biosynthesised by one of three main routes — the acetate-malonate, acetate-mevalonate or shikimic acid pathways. These pathways have been described in Chapters 4, 5 and 6, respectively. A number of aromatic compounds, however, have a mixed biogenesis, such that they are derived from products of two or more of the main pathways. Such compounds include the flavonoids, xanthones and stilbenes, whose biosynthesis involves both the shikimic acid and acetate-malonate pathways, while many plant quinones are products of the shikimic acid and acetate-mevalonate pathways.

The toxicity ofDichapetalum toxicarium for Ndama cattle

SummaryThe leaves ofDichapetalum toxicarium (G. Don) Baill. are extremely poisonous to Ndama cattle. Considerable differences in the behaviour of the animals before death were observed. Toxicity symptoms and post-mortem findings are described.

Porphyrins, Purines and Pyrimidines

The porphyrins, purines and pyrimidines are compounds with nitrogen-containing heterocyclic ring systems essential to the primary biochemical processes which maintain life. Without the porphyrin derivative, chlorophyll, there would be no de novo synthesis of sugars and therefore no energy to carry out the biochemical reactions of higher plants and animals. The nucleic acids, derivatives of purines and pyrimidines, are even more important to life, as without these compounds there would be no replication of protein molecules and no transmittance of heredity. Porphyrins, purine and pyrimidine derivatives are also involved in the prosthetic groups of many enzymes. A prosthetic group is the non-protein component of an enzyme which is firmly bound to the protein or apoenzyme, the complete complex forming a haloenzyme. More loosely bound non-protein components are known as coenzymes. A purine derivative is involved in the important complex, coenzyme A.

The Toxicity of Some Members of the Connaraceae Family

SUMMARY Cnestis corniculata, C. ferruginea, Agelea nitida, A. obliqua, A. trifolia and Byrsocarpus coccineus were found to be fatal to rabbits. The symptoms in each case were similar and resembled those of sweet clover (Melilotus) poisoning. Chemical investigation showed the presence of coumarin derivatives similar to those found in Melilotus species. As cattle are susceptible to sweet clover poisoning they are likely to be adversely affected by these members of Connaraceae.