Oxytropis, swainsonine

Within Fabaceae, Astragalus and Oxytropis are famous for the production of toxic indolizidine alkaloids, such as swainsonine, which inhibit glucosidases. These alkaloids are apparently produced by an endophyte (Embellisia spp. Pleosporaceae) (Ralphs et al., 2008). 

Ralphs, M.H., Creamer, R., Baucom, D., Gardner, D.R., Welsh, S.L., Graham, J.D., Hart, C., Cook, D. and Stegelmeier, B.L. (2008) Relationship between the endophyte Em-bellisia spp. and the toxic alkalod swainsonine in major locoweed species (Astragalus and Oxytropis). ]. Chem. EcoL, 34, 32-8. 

Polyhydroxyindolizidines are a class of alkaloids, occurring primarily in the family Leguminosae [86]. Within the group the most important members are swainsonine (1,7,8-trihydroxyindolizidine), the toxin of locoweeds Astragalus and Oxytropis species) of North America and the poison peas (Swainsona species) of Austraha, and castanospermine (1,6,7,8-tetrahydroxyindolizidine), the major alkaloid of the Moreton Bay chestnut or Black Bean Castanospermum australe). In contrast to the herbaceous locoweeds and poison peas, the latter is a large tree native of Northeastern Australia, which has been introduced as an ornamental in... 

The discovery of the indolizidine alkaloid swainsonine (35) and its A-oxide (37) in the leguminous gtn tdi Astragalus, Oxytropis, and Swainsona suggests a biosynthetic route somewhat resembling those of pyrrolizidine and quinolizidine alkaloid biosynthesis (Harris et al, 1987 Kinghom and Balandrin, 1984). The similarity of certain indolizidine alkaloids to coniine-related compounds, such as 8-coniceine (not naturally occurring) has been observed. 

Ralphs MH, Creamer R, Baucom D, Gardner DR, Welsh SL, Graham JD, Hart C, Cook D, StegelmeierBL (2008) Relation ship between theendoph5deEmbe// Mspp.andthe toxic alkaloid swainsonine in major locoweed species Astragalus and Oxytropis). J Chem Ecol 34 32-38... 

Both (lS,8aS)-(- -)-indohzidin-l-ol (88) and (lR,8a -(—)-indohzidin-l-ol (89) are intermediates in the biosynthesis of slaframine (9) and swainsonine (c Section 3.5) in the fungus Rhizoctonia legutninicolaf The former has also been isolated as the acetate from the diablo locoweed. Astragalus oxyphysus7 A related compound, 8-methylindolizidin-l-ol (90), has been claimed as a new toxic principle in extracts of Oxytropis kansuensis but details are sketchy (Figure 6). AH recent publications in this area have dealt with the synthesis of 88, 89, and the enantiomer of 89. 

Some methods for the isolation, detection, and characterization of swainso-nine (378) require mention. A novel analytical procedure based on small-scale hquid—hquid extraction of dried plant material, isolation by extraction with a cation-exchange resin, and quantitation by reversed-phase HPLC coupled to atmospheric pressure chemical ionization (APCI) tandem mass spectrometry (LC-MS/MS) was devised to ewiluate the distribution of swainsonine in populations of several North American locoweeds of the genus Oxytropis the limit of detection was about 0.001% in dry plant material, which is at the... 

Swainsonine was isolated from the Australian legume Swainsonia canescens 18) and in the United States from two species of locoweed Astragalus lentiginosum and Oxytropis sericea 19), Swainsonine is a strong inhibitor of a-mannosidase. 

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