Pyrrolizidine alkaloids. The biosynthesis of senecic acid

Crout, David H. G.; Smith, Edward H.; Davies, Noel M.; Whitehouse, David G.

doi:10.1039/p19720000671

Cited by 18 publications

(6 citation statements)

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“…In addition, evidence was provided that only C-2 to C-5 of l -leucine were incorporated into seneciphyllic acid, while C-1 (the carboxy group) was lost [107]. Feeding experiments using Senecio magnificus provided similar results for senecic acid and provided compelling evidence that the acid is derived from two molecules of l -isoleucine, both losing their C-1 during biosynthesis [108,109]. From the four possible isoleucine stereomers, l / d -isoleucine and l / d -alloisoleucine, only l -isoleucine was efficiently incorporated [110].…”

Section: Biosynthesis Of Pyrrolizidine Alkaloidsmentioning

confidence: 99%

Pyrrolizidine Alkaloids: Biosynthesis, Biological Activities and Occurrence in Crop Plants

2019

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Pyrrolizidine alkaloids (PAs) are heterocyclic secondary metabolites with a typical pyrrolizidine motif predominantly produced by plants as defense chemicals against herbivores. They display a wide structural diversity and occur in a vast number of species with novel structures and occurrences continuously being discovered. These alkaloids exhibit strong hepatotoxic, genotoxic, cytotoxic, tumorigenic, and neurotoxic activities, and thereby pose a serious threat to the health of humans since they are known contaminants of foods including grain, milk, honey, and eggs, as well as plant derived pharmaceuticals and food supplements. Livestock and fodder can be affected due to PA-containing plants on pastures and fields. Despite their importance as toxic contaminants of agricultural products, there is limited knowledge about their biosynthesis. While the intermediates were well defined by feeding experiments, only one enzyme involved in PA biosynthesis has been characterized so far, the homospermidine synthase catalyzing the first committed step in PA biosynthesis. This review gives an overview about structural diversity of PAs, biosynthetic pathways of necine base, and necic acid formation and how PA accumulation is regulated. Furthermore, we discuss their role in plant ecology and their modes of toxicity towards humans and animals. Finally, several examples of PA-producing crop plants are discussed.

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Section: Biosynthesis Of Pyrrolizidine Alkaloidsmentioning

confidence: 99%

Pyrrolizidine Alkaloids: Biosynthesis, Biological Activities and Occurrence in Crop Plants

2019

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“…This was mixed with [I-14C]-putrescine dihydrochloride and administered to 133 plants over a period of 13 days. The alkaloids were isolated (16) and purified by column chromatography. Hydrolysis gave a mixture of retronecine hydrochloride and retronecine N-oxide (17,18) in the ratio 1 to 5, as determined by 13C nmr (19) ( Table 4).…”

Section: Methods and Resultsmentioning

confidence: 99%

The biosynthesis of retronecine

Grue-Sørensen¹,

Spenser²

1982

Can. J. Chem.

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. Can. J. Chem. 60, 643 (1982). An experiment with putrescine, doubly labelled intramolecularly, with 15N and I3C at the adjacent C-atom, demonstrates that a C4-N-C4 compound with C 2 , symmetry serves as a precursor of retronecine, the most common base of the Senecio alkaloids. The C4-N-C4 compound is, in turn, generated from two ornithine-derived precursor units. This was demonstrated by a degradation sequence whereby the distribution of label from 15-I4C]-, L5-3H]-, and [4-3H]ornithine within retronecine was fully accounted for. [Traduit par le journal]

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“…Experiments with C and 3 H associated the biogenesis of the necic acids to common amino acids such as threonine, 7,8 isoleucine, 7,8 and valine. 9 In macrocyclic PAs, like Ž .…”

Section: ᎐mentioning

confidence: 99%

Pyrrolizidine alkaloids necine bases: II. Conformational analysis of free bases

Giordan

1998

J. Comput. Chem.

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Molecular mechanics calculations were applied to the conformational analysis of two diasteroisomers, the pyrrolizidine alkaloids (PAs) retronecine and heliotridine. The application of reoptimized parameters for H bonding corrected the tendency of MM3(92) calculations to give unrealistic H(DOTTED BOND)O distances for intramolecular OH interactions occurring in both diasterisomers. Inversions in the H‐bond direction of exo‐retronecine and in the relative stability of heliotridine endo–exo conformers were also observed with the application of the new parameters. A set of probable conformers was obtained for each diasterisomer, based on conformational and Boltzmann population analysis. Only exo‐puckered conformers were found in the retronecine set, whereas both exo‐ and endo‐puckered conformers were obtained for heliotridine. Transition state conformations supplied arguments supporting the design of models for H‐bond interconversion in the case of exo‐retronecine and for the exo–endo interconversion of heliotridine. Reactivity behaviors and 1H‐NMR data of both diasterisomers were elucidated in light of the theoretical results. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 1853–1861, 1998

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Pyrrolizidine alkaloids. The biosynthesis of senecic acid

Cited by 18 publications

References 0 publications

Pyrrolizidine Alkaloids: Biosynthesis, Biological Activities and Occurrence in Crop Plants

Pyrrolizidine Alkaloids: Biosynthesis, Biological Activities and Occurrence in Crop Plants

The biosynthesis of retronecine

Pyrrolizidine alkaloids necine bases: II. Conformational analysis of free bases

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