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A variety of alkaloids have been isolated from the seeds of a range of Erythrina species, including dienoid, alkenoid and lactonic derivatives. The I3C NMR spectra of these compounds have been assigned by internal comparisons within this series of related compounds and also by the use of model compounds.

The hepta-, hexa- and penta-carboxylic porphyrins found in the faeces of rats poisoned with hexachlorobenzene have been separated by high-pressure liquid chromatography and characterized largely by spectroscopie methods. Their structures were confirmed by total synthesis, as part of a programme in which eleven of the fourteen hepta-, hexa- and penta-carboxylic porphyrins derived from uroporphyrin III have now been synthesized as their methyl esters. The four isomeric heptacarboxylic and three of the pentacarboxylic porphyrinogens have been incubated with haemolysates of chicken erythrocytes, and they are all converted into protoporphyrin IX but at different rates. On the basis of this and other evidence we conclude that the decarboxylation of uroporphyrinogen III to coproporphyrinogen III is a stepwise process taking place by a preferred pathway (both in normal and abnormal metabolism); the acetic acid groups are decarboxylated in a sequential clockwise fashion starting with that on the D ring and followed by those on the A, B and C rings. In the poisoned rats the uroporphyrinogen decarboxylase enzyme (or group of enzymes) is probably partially inhibited and the pentacarboxylic porphyrinogen with an acetic acid group on ring C accumulates. The latter is then transformed by a side pathway into dehydroisocoproporphyrinogen and thence into dehydroisocoproporphyrin and its congeners.

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Take-home naloxone programs can be successfully implemented in Australian health settings. Barriers to uptake, such as lengthy processes and misperceptions around interest in overdose prevention, should be addressed in future program implementation.

Coproporphyrinogen oxidase (EC 1.3.3.3) catalyses the oxidative decarboxylation of the 2- and 4-propionate substituents of coproporphyrinogen III to form protoporphyrinogen IX. A 4-propionate-substituted porphyrinogen, harderoporphyrinogen, which is also a substrate for coproporphyrinogen oxidase, is formed during the reaction. Synthetic [(14)C]coproporphyrinogens III, specifically labelled in the carboxyl carbon atoms of either the 2- or 4-propionate substituents, were used to measure the rate of decarboxylation of each substituent by rat liver coproporphyrinogen oxidase. The experimental results, together with the recognition that in all known substrates of coproporphyrinogen oxidase only those propionate groups flanked by a specific arrangement of substituents are decarboxylated, indicate that the 4-propionate group of coproporphyrinogen III cannot be attacked until the 2-propionate group has been decarboxylated. Production of (14)CO(2) from the substrate labelled in the 2-propionate group therefore measures the formation of harderoporphyrinogen, whereas (14)CO(2) from the 4-propionate-labelled substrate measures protoporphyrinogen IX formation. The rate of harderoporphyrinogen formation is about twice that of protoporphyrinogen, and this ratio is unchanged by varying the concentration of coproporphyrinogen III or by competitive inhibition of the enzyme. When coproporphyrinogen III is present in an excess, two fractions of harderoporphyrinogen can be distinguished. One accumulates during the reaction, and the other, which is destined to become protoporphyrinogen IX, does not equilibrate with added harderoporphyrinogen. It is suggested that both decarboxylations take place at the same active centre, which becomes temporarily inaccessible to coproporphyrinogen III and added harderoporphyrinogen, and that the molecule rotates after the first decarboxylation to allow the second to take place.

~~~~ ~ lndole and its 1and 2-methyl derivatives undergo second-order azo-coupling reactions with pnitrobenzenediazonium tetrafluoroborate to afford the corresponding indole-3-azo-(4'-nitrobenzenes). Kinetic studies with related 3-deuterioindoles showed that there is no isotope effect, thus confirming that the initial attack of the electrophile is the rate-determining step, as in the majority of electrophilic aromatic substitutions.In contrast, 3-methylindole afforded 3-methylindole-2-azo-(4'-nitrobenzene) and the reaction not only showed a small deuterium isotope effect (ca. 2) but was also affected by base catalysis by water added to the acetonitrile. The difference in behaviour of the 3-methylindole from indole and its 1and 2-methyl derivatives could be accounted for by a mechanism involving primary attack of the diazonium salt at the 3-position followed by rearrangement; further evidence for this mechanism was provided by the straight line plot obtained in comparisons of the rates of reactions for the four indoles with acidity functions (which reflect protonation at the 3-position).

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