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Swainsonine

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Title: Swainsonine  
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Subject: Locoweed, Suspected female reproductive toxins, Mannosidosis, Swainsona galegifolia, Plant toxins
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Swainsonine

Swainsonine
Names
IUPAC name
(1S,2R,8R,8aR)-1,2,3,5,6,7,8,8a-Octahydroindolizine-1,2,8-triol
Other names
Tridolgosir
Identifiers
 N
ChEBI  N
ChEMBL  YesY
ChemSpider  YesY
DrugBank  YesY
Jmol-3D images Image
KEGG  YesY
PubChem
UNII  YesY
Properties
C8H15NO3
Molar mass 173.2
Melting point 143 to 144 °C (289 to 291 °F; 416 to 417 K)
10 mg/1 mL
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
 N  (: YesY/N?)

Swainsonine is an indolizidine alkaloid. It is a potent inhibitor of Golgi alpha-mannosidase II, an immunomodulator, and a potential chemotherapy drug. As a toxin in locoweed (likely its primary toxin[1]) it also is a significant cause of economic losses in livestock industries, particularly in North America.

Contents

  • Pharmacology 1
  • Sources 2
  • Biosynthesis 3
  • Livestock losses 4
  • Potential uses 5
  • See also 6
  • References 7

Pharmacology

Swainsonine inhibits glycoside hydrolases, specifically N-linked glycosylation. Disruption of Golgi alpha-mannosidase II with swainsonine induces hybrid-type glycans. These glycans have a Man5GlcNAc2 core with processing on the 3-arm that resembles so-called complex-type glycans.

The pharmacological properties of this product have not been fully investigated.

Sources

Swainsonine is a natural product that has been isolated from numerous species of flowering plants and some fungi (see Locoweed). It was first isolated from Swainsona in Australia.

Swainsonine is extracted commercially from several species of plants and fungi, including the soil fungus Metarhizium anisopliae. It also can be produced from total synthesis.

Biosynthesis

The biosynthesis of swainsonine has been investigated in the fungus Rhizoctonia leguminicola, and it initially involves the conversion of lysine into pipecolic acid. The pyrrolidine ring is then formed via retention of the carbon atom of the pipecolate's carboxyl group, as well as the coupling of two more carbon atoms from either acetate or malonate to form a pipecolylacetate. The retention of the carboxyl carbon is striking, since it is normally lost in the biosynthesis of most other alkaloids.[2]

Swainsonine Biosynthesis Scheme

The resulting oxoindolizidine is then reduced to (1R,8aS)- 1-hydroxyindolizidine, which is subsequently hydroxylated at the C2 carbon atom to yield 1,2-dihydroxyindolizidine. Finally, an 8-hydroxyl group is introduced through epimerization at C-8a to yield swainsonine. Schneider et al. have suggested that oxidation occurs at C-8a to give an iminium ion. Reduction from the β face would then yield the R configuration of swainsonine, as opposed to the S configuration of slaframine, another indolizine alkaloid whose biosynthesis is similar to that of swainsonine during the first half of the pathway and also shown above alongside that of swainsonine. The instance at which oxidation and reduction occur with regard to the introduction of the hydroxyl groups at the C2 and C8 positions is still under investigation.[2]

The biosynthetic pathway of swainsonine has also been investigated in the Diablo locoweed. Through detection of (1,8a-trans)-1-hydroxyindolizidine and (1,8a-trans-1,2-cis)-1,2-dihydroxyindolizidine—two precursors of swainsonine in the fungus pathway—in the shoots of the plant, Harris et al. proposed that the biosynthetic pathway of swainsonine in the locoweed is nearly identical to that of the fungus.[2]

Livestock losses

Because chronic intoxication with swainsonine causes a variety of neurological disorders in livestock,[3] these plant species are known collectively as locoweeds. Other effects of intoxication include reduced appetite and consequent reduced growth in young animals and loss of weight in adults, and cessation of reproduction (loss of libido, loss of fertility, and abortion).[4]

Potential uses

Swainsonine is an anti-cancer drug with potential for treating glioma[5] and gastric carcinoma.[6] However, a phase II clinical trial of GD0039 (a hydrochloride salt of swainsonine) in 17 patients with renal carcinoma was discouraging.[7] Swainsonine's activity against tumors is attributed to its stimulation of macrophages.[8]

Swainsonine also has potential uses as an adjuvant for anti-cancer drugs and other therapies in use. In mice, swainsonine reduces the toxicity of doxorubicin, suggesting that swainsonine might enable use of higher doses of doxorubicin.[9][10] Swainsonine may promote restoration of bone marrow damaged by some types of cancer treatments.[11][12]

See also

References

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  2. ^ a b c
  3. ^
  4. ^
  5. ^
  6. ^
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