Cucurbitacin Explained

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.[1] In laboratory research, cucurbitacins have cytotoxic properties and are under study for their potential biological activity.[2] [3]

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.[4] 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.[5] [6]

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.[7] 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) [7]

Variants

The cucurbitacins include:

Cucurbitacin A

Cucurbitacin B

Cucurbitacin C

Cucurbitacin D

Cucurbitacin E

Cucurbitacin F

Cucurbitacin G

Cucurbitacin H

Cucurbitacin I

Cucurbitacin J

Cucurbitacin K

Cucurbitacin L

Cucurbitacin O

Cucurbitacin P

Cucurbitacin Q

Cucurbitacin R

Cucurbitacin S

Cucurbitacin T

28/29 Norcucurbitacins

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.[4]

Other

Several other cucurbitacins have been found in plants.[4]

Occurrence and bitter taste

Constituents of the colocynth fruit and leaves (Citrullus colocynthis) include cucurbitacins.[11] [12] [13] The 2-O-β-D-glucopyranosides of cucurbitacins K and L can be extracted with ethanol from fruits of Cucurbita pepo cv dayangua.[10] Pentanorcucurbitacins A and B can be extracted with methanol from the stems of Momordica charantia.[14] Cucurbitacins B and I, and derivatives of cucurbitacins B, D and E, can be extracted with methanol from dried tubers of Hemsleya endecaphylla.[15]

Cucurbitacins impart a bitter taste in plant foods such as cucumber, zucchini, melon and pumpkin.[7]

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.[4] [2] [3] [16]

The toxicity associated with consumption of foods high in cucurbitacins is sometimes referred to as "toxic squash syndrome".[17] [18] 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.[19] Another French study of poisoning from bitter squash consumption found similar acute illnesses and no deaths.[20] The high concentration of toxin in the plants could result from cross-pollination[21] with wild cucurbitaceae species, or from plant growth stress due to high temperature and drought.[22]

See also

Notes and References

  1. Web site: Zeitung. Süddeutsche. Gift in Zucchini und Kürbis. 2020-08-21. Süddeutsche.de. 21 August 2015 . de.
  2. Alghasham AA . Cucurbitacins - a promising target for cancer therapy . International Journal of Health Sciences . 7 . 1 . 77–89 . January 2013 . 23559908 . 3612419 . 10.12816/0006025 .
  3. Kapoor S . Cucurbitacin B and its rapidly emerging role in the management of systemic malignancies besides lung carcinomas . Cancer Biotherapy & Radiopharmaceuticals . 28 . 4 . 359 . May 2013 . 23350897 . 10.1089/cbr.2012.1373 .
  4. Chen JC, Chiu MH, Nie RL, Cordell GA, Qiu SX . Cucurbitacins and cucurbitane glycosides: structures and biological activities. . Natural Product Reports . 22 . 3 . 386–99 . June 2005 . 16010347 . 10.1039/b418841c .
  5. Gamlath . Chandra B. . Gunatilaka . A. A. Leslie . Alvi . Khisal A. . Atta-ur-Rahman . Balasubramaniam . Sinnathamby . 1988-01-01 . Cucurbitacins of Colocynthis vulgaris . Phytochemistry . en . 27 . 10 . 3225–3229 . 10.1016/0031-9422(88)80031-1 . 1988PChem..27.3225G . 0031-9422.
  6. Kaushik . Ujjwal . Aeri . Vidhu . Mir . Showkat R. . 2015-05-05 . Cucurbitacins – An insight into medicinal leads from nature . . 9 . 17 . 12–18 . 10.4103/0973-7847.156314 . 26009687 . 4441156 . free .
  7. 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 HJ, Qi X, Zhang Z, Lucas WJ, Huang S . Plant science. Biosynthesis, regulation, and domestication of bitterness in cucumber . Science . 346 . 6213 . 1084–8 . November 2014 . 25430763 . 10.1126/science.1259215 . 2014Sci...346.1084S . 206561241 .
  8. Halaweish FT, Tallamy DW . A new cucurbitacin profile forCucurbita andreana: A candidate for cucurbitacin tissue culture . Journal of Chemical Ecology . 19 . 6 . 1135–41 . June 1993 . 24249132 . 10.1007/BF00987375 . 1993JCEco..19.1135H . 23549863 .
  9. 10.1016/S0031-9422(00)94223-7 . 17 . 4 . New cucurbitacins from Phormium tenax and Marah oreganus . Phytochemistry . 767–769. 1978 . Kupchan . S.Morris . Meshulam . Haim . Sneden . Albert T. . 1978PChem..17..767K .
  10. Wang DC, Pan HY, Deng XM, Xiang H, Gao HY, Cai H, Wu LJ . Cucurbitane and hexanorcucurbitane glycosides from the fruits of Cucurbita pepo cv dayangua . Journal of Asian Natural Products Research . 9 . 6–8 . 525–9 . 2007 . 17885839 . 10.1080/10286020600782538 . 27762659 .
  11. Song F, Dai B, Zhang HY, Xie JW, Gu CZ, Zhang J . 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 . 2015 . 25761128 . 10.1080/10286020.2015.1015999 . 38269788 .
  12. Chawech R, Jarraya R, Girardi C, Vansteelandt M, Marti G, Nasri I, Racaud-Sultan C, Fabre N . Cucurbitacins from the Leaves of Citrullus colocynthis (L.) Schrad . Molecules . 20 . 10 . 18001–15 . September 2015 . 26437392 . 6332406 . 10.3390/molecules201018001 . free .
  13. Kaushik . Ujjwal . January–June 2015 . Cucurbitacins – An insight into medicinal leads from nature . Pharmacogn. Rev. . v.9 . 17 . 12–18. 10.4103/0973-7847.156314 . 26009687 . 4441156 . free .
  14. Chen CR, Liao YW, Wang L, Kuo YH, Liu HJ, Shih WL, Cheng HL, Chang CI . Cucurbitane triterpenoids from Momordica charantia and their cytoprotective activity in tert-butyl hydroperoxide-induced hepatotoxicity of HepG2 cells . Chemical & Pharmaceutical Bulletin . 58 . 12 . 1639–42 . December 2010 . 21139270 . 10.1248/cpb.58.1639 . free .
  15. Chen JC, Zhang GH, Zhang ZQ, Qiu MH, Zheng YT, Yang LM, Yu KB . Octanorcucurbitane and cucurbitane triterpenoids from the tubers of Hemsleya endecaphylla with HIV-1 inhibitory activity . Journal of Natural Products . 71 . 1 . 153–5 . January 2008 . 18088099 . 10.1021/np0704396 .
  16. Kaushik U, Aeri V, Mir SR . Cucurbitacins - An insight into medicinal leads from nature . Pharmacognosy Reviews . 9 . 17 . 12–8 . 2015 . 26009687 . 4441156 . 10.4103/0973-7847.156314 . free .
  17. Shana . Kusin . Teddy . Angert . Katie . von Derau . B. Zane . Horowitz . Sandy . Giffin . 2012 Annual Meeting of the North American Congress of Clinical Toxicology (NACCT) October 1–6, 2012 las Vegas, NV, USA . 50 . 7 . 574–720 . 189. Toxic Squash Syndrome: A case series of diarrheal illness following ingestion of bitter squash, 1999-2011 . Clinical Toxicology . 10.3109/15563650.2012.700015 . 2012 . 218859008 .
  18. Web site: Poisoned by Bitter Squash, Two Women Lose Their Hair. March 28, 2018 . Live Science.
  19. Assouly P . Hair Loss Associated With Cucurbit Poisoning . JAMA Dermatology . 154 . 5 . 617–618 . May 2018 . 29590275 . 10.1001/jamadermatol.2017.6128 .
  20. Le Roux G, Leborgne I, Labadie M, Garnier R, Sinno-Tellier S, Bloch J, Deguigne M, Boels D . Poisoning by non-edible squash: retrospective series of 353 patients from French Poison Control Centers . Clinical Toxicology . 56 . 8 . 790–794 . August 2018 . 29323540 . 10.1080/15563650.2018.1424891 . 29978562 .
  21. Rymal KS, Chambliss OL, Bond MD, Smith DA . Squash Containing Toxic Cucurbitacin Compounds Occurring in California and Alabama . Journal of Food Protection . 47 . 4 . 270–271 . April 1984 . 30921968 . 10.4315/0362-028X-47.4.270 . free .
  22. Mashilo . Jacob . Odindo . Alfred O.. Shimelis . Hussein A. . Musenge . Pearl . Tesfay . Samson Z. . Magwaza . Lembe S. . Photosynthetic response of bottle gourd [Lagenaria siceraria (Molina) Standl.] to drought stress: Relationship between cucurbitacins accumulation and drought tolerance. Scientia Horticulturae . 231 . 2018 . 133–143 . 10.1016/j.scienta.2017.12.027 . 89836386 .

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