Английская Википедия:Cucurbitacin

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Файл:Cucurbitane Grundstruktur num.svg

Cucurbit-5-ene with standard carbon numbering.

Файл:Cucurbitacin-E-from-xtal-3D-st.png

3D structure of cucurbitacin E as found in the crystal structure.

Cucurbitacins are a class of biochemical compounds that some plants – notably members of the pumpkin and gourd family, Cucurbitaceae – produce and which function as a defense against herbivores. Cucurbitacins and their derivatives have also been found in many other 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 may be a taste deterrent in plants foraged by some animals and in some edible plants preferred by humans, such as cucumbers and zucchinis. In laboratory research, cucurbitacins have cytotoxic properties and are under study for their potential biological activity.

Cucurbitacins are chemically classified as triterpenes, formally derived from cucurbitane, a triterpene hydrocarbon – specifically, from the unsaturated variant cucurbit-5-ene, or 19(10→9β)-abeo-10α-lanost-5-ene. They often occur as glycosides. Most cucurbitacins are tetracyclic except some have an extra ring due to formal cyclization between C₁₆ and C₂₄ as in cucurbitacin S and cucurbitacin T.

Biosynthesis

The biosynthesis of cucurbitacin C has been described. Zhang et al. (2014) identified nine cucumber genes in the pathway for biosynthesis of cucurbitacin C and elucidated four catalytic steps. These authors also discovered the transcription factors Bl (Bitter leaf) and Bt (Bitter fruit) that regulate this pathway in leaves and fruits, respectively. The Bi gene confers bitterness to the entire plant and is genetically associated with an operon-like gene cluster, similar to the gene cluster involved in thalianol biosynthesis in Arabidopsis. Fruit bitterness requires both Bi and the dominant Bt (Bitter fruit) gene. Nonbitterness of cultivated cucumber fruit is conferred by bt, an allele selected during domestication. Bi is a member of the oxidosqualene cyclase (OSC) gene family. Phylogenetic analysis showed that Bi is the ortholog of cucurbitadienol synthase gene CPQ in squash (Cucurbita pepo) 

Variants

The cucurbitacins include:

Cucurbitacin A

Файл:Cucurbitacin A.svg

Cucurbitacin A

• Cucurbitacin A found in some species of Cucumis Шаблон:Rp
  • Pentanorcucurbitacin A, or 22-hydroxy-23,24,25,26,27-pentanorcucurbit-5-en-3-one Шаблон:Chem, white powderШаблон:Rp

Cucurbitacin B

Файл:Cucurbitacin B.svg

Cucurbitacin B

• Cucurbitacin B from Hemsleya endecaphylla (62 mg/72 g)Шаблон:Rp and other plants (e.g. Cucurbita andreana); anti-inflammatory, any-hepatotoxicШаблон:Rp
  • Cucurbitacin B 2-O-glucoside, from Begonia heracleifoliaШаблон:Rp
  • 23,24-Dihydrocucurbitacin B from Hemsleya endecaphylla, 49 mg/72 gШаблон:Rp
  • 23,24-Dihydrocucurbitacin B 2-O-glucoside from roots of Picrorhiza kurrooaШаблон:Rp
  • Deacetoxycucurbitacin B 2-O-glucoside from roots of Picrorhiza kurrooaШаблон:Rp
  • Isocucurbitacin B, from Echinocystis fabaceaШаблон:Rp
  • 23,24-Dihydroisocucurbitacin B 3-glucoside from Wilbrandia ebracteataШаблон:Rp
  • 23,24-Dihydro-3-epi-isocucurbitacin B, from Bryonia verrucosaШаблон:Rp
  • Pentanorcucurbitacin B or 3,7-dioxo-23,24,25,26,27-pentanorcucurbit-5-en-22-oic acid, Шаблон:Chem, white powderШаблон:Rp

Cucurbitacin C

• Cucurbitacin C, from Cucumis sativus (cucumber)Шаблон:Rp

Cucurbitacin D

Файл:Cucurbitacin D.svg

Cucurbitacin D

• Cucurbitacin D, from Trichosanthes kirilowii and many other plants (e.g. Cucurbita andreana)Шаблон:Rp
  • 3-Epi-isocucurbitacin D, from species of PhysocarpusШаблон:Rp and Phormium tenax
  • 22-Deoxocucurbitacin D from Hemsleya endecaphylla, 14 mg/72 gШаблон:Rp
  • 23,24-Dihydrocucurbitacin D from Trichosanthes kirilowiiШаблон:Rp also from H. endecaphylla, 80 mg/72 gШаблон:Rp
  • 23,24-Dihydro-epi-isocucurbitacin D, from Acanthosicyos horridusШаблон:Rp
  • 22-Deoxocucurbitacin D from Wilbrandia ebracteataШаблон:Rp
  • Anhydro-22-deoxo-3-epi-isocucurbitacin D from Ecballium elateriumШаблон:Rp
  • 25-O-Acetyl-2-deoxycucurbitacin D (amarinin) from Luffa amaraШаблон:Rp
  • 2-Deoxycucurbitacin D, from Sloanea zuliaensisШаблон:Rp

Cucurbitacin E

• Cucurbitacin E (α-Elaterin), from roots of Wilbrandia ebracteata. Strong antifeedant for the flea beetle, inhibits cell adhesion (also in e.g. Cucurbita andreana)Шаблон:Rp
  • 22,23-Dihydrocucurbitacin E from Hemsleya endecaphylla, 9 mg/72 g,Шаблон:Rp and from roots of Wilbrandia ebracteataШаблон:Rp
  • 22,23-Dihydrocucurbitacin E 2-glucoside from roots of Wilbrandia ebracteataШаблон:Rp
  • Isocucurbitacin E, from Cucumis prophetarumШаблон:Rp
  • 23,24-Dihydroisocucurbitacin E, from Cucumis prophetarumШаблон:Rp

Cucurbitacin F

• Cucurbitacin F from Elaeocarpus dolichostylusШаблон:Rp
  • Cucurbitacin F 25-acetate from Helmseya gracilifloraШаблон:Rp
  • 23,24-Dihydrocucurbitacin F from Helmseya amabilisШаблон:Rp
  • 25-Acetoxy-23,24-dihydrocucurbitacin F from Helmseya amabilis (hemslecin A)Шаблон:Rp
  • 23,24-Dihydrocucurbitacin F glucoside from Helmseya amabilisШаблон:Rp
  • Cucurbitacin II glucoside from Helmseya amabilisШаблон:Rp
  • Hexanorcucurbitacin F from Elaeocarpus dolichostylusШаблон:Rp
  • Perseapicroside A from Persea mexicanaШаблон:Rp
  • Scandenoside R9 from Hemsleya panacis-scandensШаблон:Rp
  • 15-Oxo-cucurbitacin F from Cowania mexicanaШаблон:Rp
  • 15-oxo-23,24-dihydrocucurbitacin F from Cowania mexicanaШаблон:Rp
  • Datiscosides B, D, and H, from Datisca glomerataШаблон:Rp

Cucurbitacin G

• Cucurbitacin G from roots of Wilbrandia ebracteataШаблон:Rp
• 3-Epi-isocucurbitacin G, from roots of Wilbrandia ebracteataШаблон:Rp

Cucurbitacin H

• Cucurbitacin H, stereoisomer of cucurbitacin G, from roots of Wilbrandia ebracteataШаблон:Rp

Cucurbitacin I

Файл:Cucurbitacin I.svg

Cucurbitacin I

• Cucurbitacin I (elatericin B) from Hemsleya endecaphylla, 10 mg/72 g,Шаблон:Rp also from Ecballium elaterium Citrullus colocynthis, Cucurbita andreana, deters feeding by flea beetleШаблон:Rp
  • Hexanorcucurbitacin I from Ecballium elateriumШаблон:Rp
  • 23,24-Dihydrocucurbitacin I see Cucurbitacin L
  • Khekadaengosides D and K from the fruits of Trichosanthes tricuspidataШаблон:Rp
  • 11-Deoxocucurbitacin I, from Desfontainia spinosaШаблон:Rp
  • Spinosides A and B, from Desfontainia spinosaШаблон:Rp
  • 23,24-dihydro-11-Deoxocucurbitacin I from Desfontainia spinosaШаблон:Rp

Cucurbitacin J

• Cucurbitacin J from Iberis amaraШаблон:Rp
  • Cucurbitacin J 2-O-β-glucopyranoside from Trichosanthes tricuspidataШаблон:Rp

Cucurbitacin K

• Cucurbitacin K, stereoisomer of cucurbitacin J,Шаблон:Rp from Iberis amaraШаблон:Rp
  • Cucurbitacin K 2-O-β-glucopyranoside from Trichosanthes tricuspidataШаблон:Rp

Cucurbitacin L

• Cucurbitacin L, or 23,24-dihydrocucurbitacin I,Шаблон:RpШаблон:Rp
  • Brydioside A from Bryonia dioicaШаблон:Rp
  • Bryoamaride from Bryonia dioicaШаблон:Rp
  • 25-O-Acetylbryoamaride from Trichosanthes tricuspidataШаблон:Rp
  • Khekadaengosides A and B from Trichosanthes tricuspidataШаблон:Rp

Cucurbitacin O

• Cucurbitacin O from Brandegea bigeloviiШаблон:Rp
  • Cucurbitacin Q 2-O-glucoside, from Picrorhiza kurrooaШаблон:Rp
  • 16-Deoxy-D-16-hexanorcucurbitacin O from Ecballium elateriumШаблон:Rp
  • Deacetylpicracin from Picrorhiza scrophulariaefloraШаблон:Rp
  • Deacetylpicracin 2-O-glucoside from Picrorhiza scrophulariaefloraШаблон:Rp
  • 22-Deoxocucurbitacin O from Wilbrandia ebracteataШаблон:Rp

Cucurbitacin P

• Cucurbitacin P from Brandegea bigeloviiШаблон:Rp
  • Picracin from Picrorhiza scrophulariaefloraШаблон:Rp
  • Picracin 2-O-glucoside from Picrorhiza scrophulariaefloraШаблон:Rp

Cucurbitacin Q

Файл:Cucurbitacin Q.svg

Cucurbitacin Q

• Cucurbitacin Q from Brandegea bigeloviiШаблон:Rp
  • 23,24-Dihydrodeacetylpicracin 2-O-glucoside from Picrorhiza kurrooaШаблон:Rp
  • Cucurbitacin Q1 from Cucumis species, actually Cucurbitacin F 25-acetate

Cucurbitacin R

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

Cucurbitacin S

• Cucurbitacin S from Bryonia dioicaШаблон:Rp

Cucurbitacin T

• Cucurbitacin T, from the fruits of Citrullus colocynthisШаблон:Rp

28/29 Norcucurbitacins

Шаблон:Expand section There are several substances that can be seen as deriving from cucurbit-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.Шаблон:Rp

Other

Шаблон:Expand section Several other cucurbitacins have been found in plants.Шаблон:Rp

Occurrence and bitter taste

Файл:Ecballium elaterium fruit and flower.jpg

Fruit and flower of the Ecballium elaterium, also called the squirting cucumber or exploding cucumber containing cucurbitacin B

Constituents of the colocynth fruit and leaves (Citrullus colocynthis) include cucurbitacins. The 2-O-β-D-glucopyranosides of cucurbitacins K and L can be extracted with ethanol from fruits of Cucurbita pepo cv dayangua. Pentanorcucurbitacins A and B can be extracted with methanol from the stems of Momordica charantia. Cucurbitacins B and I, and derivatives of cucurbitacins B, D and E, can be extracted with methanol from dried tubers of Hemsleya endecaphylla.

Cucurbitacins impart a bitter taste in plant foods such as cucumber, zucchini, melon and pumpkin.

Research and toxicity

Cucurbitacins are under basic research for their biological properties, including toxicity and potential pharmacological uses in development of drugs for inflammation, cancer, cardiovascular diseases, and diabetes, among others.

The toxicity associated with consumption of foods high in cucurbitacins is sometimes referred to as "toxic squash syndrome". In France in 2018, two women who ate soup made from bitter pumpkins became sick, involving nausea, vomiting, and diarrhea, and had hair loss weeks later. Another French study of poisoning from bitter squash consumption found similar acute illnesses and no deaths. The high concentration of toxin in the plants could result from cross-pollination with wild cucurbitaceae species, or from plant growth stress due to high temperature and drought.

See also

• Goyaglycoside
• Hemslecin
• Mogroside
• Momordicine
• Momordicoside
• Neomogroside
• Scandenosides R1–R8, R10-R11
• Siamenoside I