Australine, a Novel Pyrrolizidine Alkaloid Glucosidase Inhibitor from Castanospermum australe

Abstract

stitution pattern, has been isolated from seeds of Castanospermum australe and shown to be a potent and specific inhibitor of amyloglucosidase. The structure was established by a combination of spectroscopic and chemical techniques and confirmed by X-ray crystallography. Australine is the first pyrrolizidine alkaloid to be identified as a glycosidase inhibitor and is the third glucosidase inhibitor, together with the indolizidine alkaloids castanospermine [2] and 6-epicastanospermine [3], to be isolated from C. australe. In addition to these bicyclic alkaloids, the piperidine alkaloid fagomine [5], a non-inhibitor, has been isolated from the seeds. Castanospermum australe A. Cunn. (Leguminosae), the Moreton Bay chestnut or black bean and the monotypic species of the genus Castanospermum native to northeastern Australia, has been introduced into the Indian subcontinent, South Africa, and mild climate areas of North America as an ornamental tree (1). Castanospermine [2],

Evolution of Homospermidine Synthase in the Convolvulaceae: A Story of Gene Duplication, Gene Loss, and Periods of Various Selection Pressures

“…Of note, I. alba produces indolizidine alkaloids, compounds with a fused sixand five-membered ring containing a heterocyclic nitrogen and showing slight structural resemblance to PAs (Gourley et al, 1969;Ikhiri et al, 1987). In Castanospermum australe (Fabaceae), PAs co-occur with indolizidine alkaloids (Molyneux et al, 1988). Further research should reveal whether the HSS-like enzyme is involved in the biosynthesis of these compounds.…”

Asymmetric synthesis of (+)-1-epiaustraline and attempted synthesis of australine

“…Base hydrolysis of 11 followed by ion-exchange chromatography gave 12 which was cyclized to the desired pyrrolizidine ring system under Mitsunobu conditions 12,19 in pyridine at 0 o C. The crude reaction mixture was then treated under hydrogenolysis conditions 12,13,20 and then peracetylation gave the pyrrolizidine-tetraacetate 15 in 23% over yield from 11. Scheme 2 outlines our attempted synthesis of australine (2). This synthesis required inversion of the stereochemistry at C-7 in the pyrrolo [1,2-c]oxazol-3-one 9.…”

“…1 In the same year its 7a-epimer, australine (2), was isolated from the seeds of Castanospermum australe. 2 Later reports described the isolation of other epimers of 2 from these seeds, including 1-epiaustraline…”

Insecticidal Activity of Castanospermum australe against stored Grain Pest Callosobruchus analis

“…In traditional medicine, the pods of the plant are reported as astringent [8] and In treatment of post pyrandial hyperglycemia in diabetic patients [9]. On literature survey it was found that the wood of Castanospermum australe contains castanogenin and bayogenin [10] whereas castanogenol from bark [11], castanospermine [12] and australine [13] from seed are reported. Saponins from the fresh leaves of Castanospermum australe have also been characterized [14,15].…”