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Cucurbitacin

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Cucurbitacin

Cucurbitacin is any of a class of biochemical compounds that some plants — notably members of the family Cucurbitaceae, that includes the common pumpkins and gourds — developed in order to defend themselves from herbivores. Cucurbitacins are chemically classified as steroids, formally derived from cucurbitane, a triterpene hydrocarbon — specifically, from the unsaturated variant cucurbita-5-ene, or 19-(10→9β)-abeo-10α-lanost-5-ene. They often occur as glycosides.[1] They and their derivatives have been found in many plant families (including Brassicaceae, Cucurbitaceae, Scrophulariaceae, Begoniaceae, Elaeocarpaceae, Datiscaceae, Desfontainiaceae, Polemoniaceae, Primulaceae, Rubiaceae, Sterculiaceae, Rosaceae, and Thymelaeaceae), in some mushrooms (including Russula and Hebeloma) and even in some marine mollusks.

Cucurbitacins are generally cytotoxic and poisonous to some animals, and some of them are among the bitterest tastes to humans. Many have also been investigated for other biological activities.[2][3][4][5][6]

Variants

The cucurbitacins include:

Cucurbitacin A

  • Cucurbitacin A found in some species of Cucumis [1]:1
    • Pentanorcucurbitacin A, or 22-hydroxy-23,24,25,26,27-pentanorcucurbit-5-en-3-one , white powder[7]:1

Cucurbitacin B

  • Cucurbitacin B from Hemsleya endecaphylla (62 mg/72 g)[8]:4 and other plants; anti-inflammatory, any-hepatotoxic [1]:2
    • Cucurbitacin B 2-O-glucoside, from Begonia heracleifolia [1]:3
    • 23,24-Dihydrocucurbitacin B from Hemsleya endecaphylla, 49 mg/72 g[8]:5
    • 23,24-Dihydrocucurbitacin B 2-O-glucoside from roots of Picrorhiza kurrooa [1]:4
    • Deacetoxycucurbitacin B 2-O-glucoside from roots of Picrorhiza kurrooa [1]:5
    • Isocucurbitacin B, from Echinocystis fabacea [1]:6
    • 23,24-Dihydroisocucurbitacin B 3-glucoside from Wilbrandia ebracteata [1]:7
    • 23,24-Dihydro-3-epi-isocucurbitacin B, from Bryonia verrucosa [1]:8
    • Pentanorcucurbitacin B or 3,7-dioxo-23,24,25,26,27-pentanorcucurbit-5-en-22-oic acid, , white powder[7]:2

Cucurbitacin C

  • Cucurbitacin C, from Cucumis sativus (Cucumber) [1]:11

Cucurbitacin D

  • Cucurbitacin D, from Trichosanthes kirilowii and many other plants [1]:12
    • 3-Epi-isocucurbitacin D, from species of Physocarpus [1]:14 and Phormium tenax[9]
    • 22-Deoxocucurbitacin D from Hemsleya endecaphylla, 14 mg/72 g[8]:6
    • 23,24-Dihydrocucurbitacin D from Trichosanthes kirilowii [1]:13 also from H. endecaphylla, 80 mg/72 g[8]:3
    • 23,24-Dihydro-epi-isocucurbitacin D, from Acanthosicyos horridus [1]:20
    • 22-Deoxocucurbitacin D from Wilbrandia ebracteata [1]:21
    • Anhydro-22-deoxo-3-epi-isocucurbitacin D from Ecballium elaterium [1]:22
    • 25-O-Acetyl-2-deoxycucurbitacin D (amarinin) from Luffa amara [1]:24
    • 2-Deoxycucurbitacin D, from Sloanea zuliaensis [1]:23

Cucurbitacin E

  • Cucurbitacin E (aelaterin), from roots of Wilbrandia ebracteata. Strong antifeedant for the flea beetle, inhibits cell adhesion [1]:27
    • 22,23-Dihydrocucurbitacin E from Hemsleya endecaphylla, 9 mg/72 g[8]:8, and from roots of Wilbrandia ebracteata [1]:28
    • 22,23-Dihydrocucurbitacin E 2-glucoside from roots of Wilbrandia ebracteata [1]:29
    • Isocucurbitacin E, from Cucumis phrophetarum [1]:30
    • 23,24-Dihydroisocucurbitacin E, from Cucumis phrophetarum [1]:31

Cucurbitacin F

  • Cucurbitacin F from Elaeocarpus dolichostylus [1]:33
    • Cucurbitacin F 25-acetate from Helmseya graciliflora [1]:34
    • 23,24-Dihydrocucurbitacin F from Helmseya amabilis [1]:35
    • 25-Acetoxy-23,24-dihydrocucurbitacin F from Helmseya amabilis (hemslecin A) [1]:36
    • 23,24-Dihydrocucurbitacin F glucoside from Helmseya amabilis [1]:40
    • Cucurbitacin II glucoside from Helmseya amabilis [1]:41
    • Hexanorcucurbitacin F from Elaeocarpus dolichostylus [1]:43
    • Perseapicroside A from Persea mexicana [1]:44
    • Scandenoside R9 from Hemsleya panacis-scandens [1]:45
    • 15-Oxo-cucurbitacin F from Cowania mexicana [1]:46
    • 15-oxo-23,24-dihydrocucurbitacin F from Cowania mexicana [1]:47
    • Datiscosides B, D, and H, from Datisca glomerata [1]:48–50

Cucurbitacin G

  • Cucurbitacin G from roots of Wilbrandia ebracteata [1]:52
  • 3-Epi-isocucurbitacin G, from roots of Wilbrandia ebracteata [1]:54

Cucurbitacin H

  • Cucurbitacin H, stereoisomer of cucurbitacin G, from roots of Wilbrandia ebracteata [1]:53

Cucurbitacin I

  • Cucurbitacin I (elatericin B) from Hemsleya endecaphylla, 10 mg/72 g [8]:7, also from Ecballium elaterium and Citrullus colocynthis, deters feeding by flea beetle [1]:55
    • Hexanorcucurbitacin I from Ecballium elaterium [1]:56
    • 23,24-Dihydrocucurbitacin I see Cucurbitacin L
    • Khekadaengosides D and K from the fruits of Trichosanthes tricuspidata [1]:57,58
    • 11-Deoxocucurbitacin I, from Desfontainia spinosa [1]:59
    • Spinosides A and B, from Desfontainia spinosa [1]:61,62
    • 23,24-dihydro-11-Deoxocucurbitacin I from Desfontainia spinosa [1]:60

Cucurbitacin J

  • Cucurbitacin J from Iberis amara [1]:69
    • Cucurbitacin J 2-O-β-glucopyranoside from Trichosanthes tricuspidata [1]:71

Cucurbitacin K

  • Cucurbitacin K, stereoisomer of cucurbitacin J,[10]:2, from Iberis amara [1]:70
    • Cucurbitacin K 2-O-β-glucopyranoside from Trichosanthes tricuspidata [1]:72

Cucurbitacin L

  • Cucurbitacin L, or 23,24-dihydrocucurbitacin I,[1]:63 [10]:1
    • Brydioside A from Bryonia dioica [1]:64
    • Bryoamaride from Bryonia dioica [1]:65
    • 25-O-Acetylbryoamaride from Trichosanthes tricuspidata [1]:66
    • Khekadaengosides A and B from Trichosanthes tricuspidata [1]:67–68

Cucurbitacin O

  • Cucurbitacin O from Brandegea bigelovii [1]:73
    • Cucurbitacin Q 2-O-glucoside, from Picrorhiza kurrooa [1]:76
    • 16-Deoxy-D-16-hexanorcucurbitacin O from Ecballium elaterium [1]:77
    • Deacetylpicracin from Picrorhiza scrophulariaeflora [1]:78
    • Deacetylpicracin 2-O-glucoside from Picrorhiza scrophulariaeflora [1]:80
    • 22-Deoxocucurbitacin O from Wilbrandia ebracteata [1]:83

Cucurbitacin P

  • Cucurbitacin P from Brandegea bigelovii [1]:74
    • Picracin from Picrorhiza scrophulariaeflora [1]:79
    • Picracin 2-O-glucoside from Picrorhiza scrophulariaeflora [1]:79

Cucurbitacin Q

  • Cucurbitacin Q from Brandegea bigelovii [1]:75
    • 23,24-Dihydrodeacetylpicracin 2-O-glucoside from Picrorhiza kurrooa [1]:82
    • Cucurbitacin Q1 from Cucumis species, actually Cucurbitacin F 25-acetate [1]

Cucurbitacin R

  • Cucurbitacin R is actually 23,24-dihydrocucurbitacin D.[1]

Cucurbitacin S

Cucurbitacin T

28/29 Norcucurbitacins

There are several substances that can be seen as derving from cucurbita-5-ene skeleton by loss of one of the methyl groups (28 or 29) attached to carbon 4; often with the adjacent ring (ring A) becoming aromatic.[1]:87–130

Other

Several other cucurbitacins have been found in plants.[1]:152–156,164–165

Occurrence

One of the active constituents of the colocynth fruit (Citrullus colocynthis) is a cucurbitacin.

The 2-O-β-D-glucopyranosides of Cucurbitacins K and L can be extracted with ethanol from fruits of Cucurbita pepo cv dayangua, at concentrations of 40 mg/15 kg and 32 mg/15 kg, respectively.[10]

Pentanorcucurbitacins A and B can be extracted with methanol from the stems of Momordica charantia, at concentrations of 1 mg/18 kg and 4.5 mg/18 kg, respectively.[7]

Cucurbitacins B and I, and derivatives of cucurbitacins B, D and E, can be extracted with methanol from dried tubers of Hemsleya endecaphylla at the concentrations shown above.[8]

Uses

Some cucurbitacins have the action of a potent cathartic purgative.

Some cucurbitacins and their derivatives are also cytotoxic. The toxicity of one cucurbitacin is enhanced by the introduction of a double bond at carbon C23, of an acetyl group at C25, or a double bond at carbons C1-C2. It is decreased by reduction of the ketone group at C3, or introduction of a hydroxyl group at C24. The compound cucurbitacin E is particularly cytotoxic; a concentration of 4.5×10−7μg/ml will destroy half of the cancer cells present.

See also

References

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