Cucurbitacin

Cucurbita-5-ene with standard carbon numbering.

Cucurbitacin is any of a class of biochemical compounds that some plants — notably members of the family Cucurbitaceae, which includes the common pumpkins and gourds — produce and which function as a defence against herbivores. Cucurbitacins are chemically classified as triterpenes, 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 may be a taste deterrent in plants foraged by some animals and in some edible plants preferred by humans, like cucumbers. In laboratory research, cucurbitacins have cytotoxic properties and are under study for their potential biological activities.[2][3]

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.[4] 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) [4]

Variants

The cucurbitacins include:

Cucurbitacin A

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 C
      25      H
      40      O
      2      , white powder[5]:1

Cucurbitacin B

Cucurbitacin B
  • Cucurbitacin B from Hemsleya endecaphylla (62 mg/72 g)[6]:4 and other plants (e.g. Cucurbita andreana[7]); 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[6]: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, C
      25      H
      36      O
      4      , white powder[5]:2

Cucurbitacin C

Cucurbitacin D

Cucurbitacin D

Cucurbitacin E

  • Cucurbitacin E (aelaterin), from roots of Wilbrandia ebracteata. Strong antifeedant for the flea beetle, inhibits cell adhesion [1] (also in e.g. Cucurbita andreana[7]):27
    • 22,23-Dihydrocucurbitacin E from Hemsleya endecaphylla, 9 mg/72 g,[6]: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 prophetarum [1]:30
    • 23,24-Dihydroisocucurbitacin E, from Cucumis prophetarum [1]:31

Cucurbitacin F

  • Cucurbitacin F from Elaeocarpus dolichostylus [1]:33

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

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,[9]:2 from Iberis amara [1]:70
    • Cucurbitacin K 2-O-β-glucopyranoside from Trichosanthes tricuspidata [1]:72

Cucurbitacin L

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
  • 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 and bitter taste

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.[10][11] The 2-O-β-D-glucopyranosides of cucurbitacins K and L can be extracted with ethanol from fruits of Cucurbita pepo cv dayangua.[9] Pentanorcucurbitacins A and B can be extracted with methanol from the stems of Momordica charantia.[5] Cucurbitacins B and I, and derivatives of cucurbitacins B, D and E, can be extracted with methanol from dried tubers of Hemsleya endecaphylla.[6]

Cucurbitacins impart a bitter taste in plant foods such as cucumber, zucchini, melon and pumpkin.[12][13]

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.[1][2][3][12]

The toxicity associated with consumption of foods high in cucurbatincs is sometimes referred to as "toxic squash syndrome".[14][15] 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.[16] Another French study of poisoning from bitter squash consumption found similar acute illnesses and no deaths.[17] The high concentration of toxin in the plants could result from cross-pollination[18] with wild cucurbitaceae species, or from plant growth stress due to high temperature and drought.[19]

Pathologists found cucurbitacin in the stomach of a 79-year-old man who died in Bavaria, Germany, shortly after eating a casserole containing zucchini he had received from a neighbor.[20][21]

See also

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 Jian Chao Chen, Ming Hua Chiu, Rui Lin Nie, Geoffrey A. Cordell and Samuel X. Qiu (2005), "Cucurbitacins and cucurbitane glycosides: structures and biological activities" Natural Product Reports, volume 22, pages 386-399 doi:10.1039/B418841C
  2. 1 2 Alghasham, AA (2013). "Cucurbitacins - a promising target for cancer therapy". International Journal of Health Sciences. 7 (1): 77–89. doi:10.12816/0006025. PMC 3612419. PMID 23559908.
  3. 1 2 Kapoor, S (2013). "Cucurbitacin B and Its Rapidly Emerging Role in the Management of Systemic Malignancies Besides Lung Carcinomas". Cancer Biotherapy and Radiopharmaceuticals. 28 (4): 359. doi:10.1089/cbr.2012.1373. PMID 23350897.
  4. 1 2 Zhang, Y.; et al. (2014). "Biosynthesis, regulation, and domestication of bitterness in cucumber". Science. 346 (6213): 1084–1088. Bibcode:2014Sci...346.1084S. doi:10.1126/science.1259215. PMID 25430763.
  5. 1 2 3 Chen, Chiy-Rong; Liao, Yun-Wen; Wang, Lai; Kuo, Yueh-Hsiung; Liu, Hung-Jen; Shih, Wen-Ling; Cheng, Hsueh-Ling; Chi-I, Chang (2010). "Cucurbitane Triterpenoids from Momordica charantia and Their Cytoprotective Activity in tert-Butyl Hydroperoxide-Induced Hepatotoxicity of HepG2 Cells". Chemical & Pharmaceutical Bulletin. 58 (12): 1639–1642. doi:10.1248/cpb.58.1639.
  6. 1 2 3 4 5 6 7 Chen, Jian-Chao; Zhang, Gao-Hong; Zhang, Zhong-Quan; Qiu, Ming-Hua; Zheng, Yong-Tang; Yang, Liu-Meng; Yu, Kai-Bei (2008). "Octanorcucurbitane and Cucurbitane Triterpenoids from the Tubers of Hemsleya endecaphylla with HIV-1 Inhibitory Activity". J. Nat. Prod. 71 (1): 153–155. doi:10.1021/np0704396. PMID 18088099.
  7. 1 2 3 4 Halaweish, FT; Tallamy, DW (1993). "A new cucurbitacin profile for Cucurbita andreana: A candidate for cucurbitacin tissue culture". Journal of Chemical Ecology. 19 (6): 1135–1141. doi:10.1007/BF00987375. PMID 24249132.
  8. ↑ Kupchan, S.Morris; Meshulam, Haim; Sneden, Albert T. (1978). "New cucurbitacins from Phormium tenax and Marah oreganus". Phytochemistry. 17 (4): 767–769. doi:10.1016/S0031-9422(00)94223-7.
  9. 1 2 3 Wang, Da-Cheng; Pan, Hong-Yu; Deng, Xu-Ming; Xiang, Hua; Gao, Hui-Yuan; Cai, Hui; Wu, Li-Jun (2007). "Cucurbitane and hexanorcucurbitane glycosides from the fruits of Cucurbita pepo cv dayangua"". Journal of Asian Natural Products Research. 9 (6): 525–529. doi:10.1080/10286020600782538.
  10. ↑ Song, F; Dai, B; Zhang, H. Y.; Xie, J. W.; Gu, C. Z.; Zhang, J (2015). "Two new cucurbitane-type triterpenoid saponins isolated from ethyl acetate extract of Citrullus colocynthis fruit". Journal of Asian Natural Products Research. 17 (8): 813–8. doi:10.1080/10286020.2015.1015999. PMID 25761128.
  11. ↑ Chawech, R; Jarraya, R; Girardi, C; Vansteelandt, M; Marti, G; Nasri, I; Racaud-Sultan, C; Fabre, N (2015). "Cucurbitacins from the Leaves of Citrullus colocynthis (L.) Schrad". Molecules. 20 (10): 18001–15. doi:10.3390/molecules201018001. PMID 26437392.
  12. 1 2 Kaushik, U; Aeri, V; Mir, S. R (2015). "Cucurbitacins – an insight into medicinal leads from nature". Pharmacognosy Reviews. 9 (17): 12–18. doi:10.4103/0973-7847.156314. PMC 4441156. PMID 26009687.
  13. ↑ Shang, Y; Ma, Y; Zhou, Y; Zhang, H; Duan, L; Chen, H; Zeng, J; Zhou, Q; Wang, S; Gu, W; Liu, M; Ren, J; Gu, X; Zhang, S; Wang, Y; Yasukawa, K; Bouwmeester, H. J.; Qi, X; Zhang, Z; Lucas, W. J.; Huang, S (2014). "Plant science. Biosynthesis, regulation, and domestication of bitterness in cucumber". Science. 346 (6213): 1084–8. Bibcode:2014Sci...346.1084S. doi:10.1126/science.1259215. PMID 25430763.
  14. ↑ Shana Kusin, Teddy Angert, Katie von Derau, B. Zane Horowitz, Sandy Giffin (2012). "189. Toxic Squash Syndrome: A case series of diarrheal illness following ingestion of bitter squash, 1999-2011" (PDF). 2012 Annual Meeting of the North American Congress of Clinical Toxicology (NACCT) October 1–6, 2012 Las Vegas, NV, USA. 50 (7): 574–720. doi:10.3109/15563650.2012.700015.
  15. ↑ "Poisoned by Bitter Squash, Two Women Lose Their Hair". Live Science. March 28, 2018.
  16. ↑ Assouly, Philippe (2018). "Hair loss associated with cucurbit poisoning". JAMA Dermatology. 154 (5): 617–618. doi:10.1001/jamadermatol.2017.6128. ISSN 2168-6068. PMID 29590275.
  17. ↑ Le Roux, G.; Leborgne, I.; Labadie, M.; Garnier, R.; Sinno-Tellier, S.; Bloch, J.; Deguigne, M.; Boels, D. (2018). "Poisoning by non-edible squash: retrospective series of 353 patients from French Poison Control Centers". Clinical Toxicology. 56 (8): 1–6. doi:10.1080/15563650.2018.1424891. ISSN 1556-3650.
  18. ↑ Rymal, K. S; Chambliss, O. L; Bond, M. D; Smith, D. A (1984). "Squash Containing Toxic Cucurbitacin Compounds Occurring in California and Alabama". Journal of Food Protection. 47 (4): 270. doi:10.4315/0362-028X-47.4.270.
  19. ↑ Mashilo, Jacob; Odindo, Alfred O.; Shimelis, Hussein A.; Musenge, Pearl; Tesfay, Samson Z.; Magwaza, Lembe S. (2018). "Photosynthetic response of bottle gourd [Lagenaria siceraria (Molina) Standl.] to drought stress: Relationship between cucurbitacins accumulation and drought tolerance". Scientia Horticulturae. 231: 133–143. doi:10.1016/j.scienta.2017.12.027. ISSN 0304-4238.
  20. ↑ "Mann stirbt an Garten Zucchini". Retrieved 24 August 2015.
  21. ↑ "Auf den Geschmack kommt es an". Retrieved 24 August 2015.
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