| In vitro: |
| J Nat Prod. 1996 Dec;59(12):1137-42. | | Biological activities of the nortropane alkaloid, calystegine B2, and analogs: structure-function relationships.[Pubmed: 8988598 ] |
METHODS AND RESULTS:
Calystegines, polyhydroxy nortropane alkaloids, are a recently discovered group of plant secondary metabolites believed to influence rhizosphere ecology as nutritional sources for soil microorganisms and as glycosidase inhibitors.
Evidence is presented that calystegines mediate nutritional relationships under natural conditions and that their biological activities are closely correlated with their chemical structures and stereochemistry. Assays using synthetic (+)- and (-)-enantiomers of calystegine B2 established that catabolism by Rhizobium meliloti, glycosidase inhibition, and allelopathic activities were uniquely associated with the natural, (+)-enantiomer. Furthermore, the N-methyl derivative of calystegine B2 was not catabolized by R. meliloti, and it inhibited alpha-galactosidase, but not beta-glucosidase, whereas the parent alkaloid inhibits both enzymes.
CONCLUSIONS:
This N-methyl analog therefore could serve to construct a cellular or animal model for Fabry's disease, which is caused by a lack of alpha-galactosidase activity. |
|
| In vivo: |
| J Nat Prod. 1995 Jun;58(6):878-86. | | Identification of the glycosidase inhibitors swainsonine and calystegine B2 in Weir vine (Ipomoea sp. Q6 [aff. calobra]) and correlation with toxicity.[Pubmed: 7673932] |
METHODS AND RESULTS:
The polyhydroxy alkaloid glycosidase inhibitors swainsonine [1] and calystegine B2 [6] have been identified as constituents of the seeds of the Australian plant Ipomoea sp. Q6 [aff. calobra] (Weir vine) by gas chromatography-mass spectrometry and by their biological activity as inhibitors of specific glycosidases. This plant, which is known only from a small area of southern Queensland, has been reported to produce a neurological disorder when consumed by livestock. The extract of the seeds showed inhibition of alpha-mannosidase, beta-glucosidase, and alpha-galactosidase, consistent with the presence of 1 and alkaloids of the calystegine class. Histological examination of brain tissue from field cases of sheep and cattle poisoned by Weir vine showed lesions similar to those observed in animals poisoned by the swainsonine-containing poison peas (Swainsona spp.) of Australia and locoweeds (Astragalus and Oxytropis spp.) of North America.
CONCLUSIONS:
These results indicate that Weir vine poisoning is an additional manifestation of the induced lysosomal storage disease, mannosidosis, possibly exacerbated by inhibition of the enzymes beta-glucosidase and alpha-galactosidase by calystegine B2.
This is the first reported example of a single plant species capable of producing structurally distinct glycosidase inhibitors, namely, alkaloids of the indolizidine and nortropane classes. |
|
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