Cucurbitacins may be a taste deterrent in plants foraged by some animals and in some edible plants preferred by humans, such ascucumbers andzucchinis.[1] Inlaboratory research, cucurbitacins havecytotoxic properties and are under study for their potential biological activity.[2][3]
The biosynthesis of cucurbitacin C has been described. Zhang et al. (2014) identified ninecucumber genes in the pathway for biosynthesis of cucurbitacin C and elucidated four catalytic steps.[7] These authors also discovered thetranscription factorsBl (Bitter leaf) andBt (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 anoperon-like gene cluster, similar to the gene cluster involved inthalianol biosynthesis inArabidopsis. 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 theortholog of cucurbitadienol synthase gene CPQ in squash (Cucurbita pepo) [7]
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There are several substances that can be seen as deriving from cucurbit-5-ene skeleton by loss of one of themethyl groups (28 or 29) attached to carbon 4; often with the adjacent ring (ring A) becomingaromatic.[4]: 87–130
Constituents of thecolocynth fruit and leaves (Citrullus colocynthis) include cucurbitacins.[13][14][15] The 2-O-β-D-glucopyranosides of cucurbitacins K and L can be extracted withethanol from fruits ofCucurbita pepocvdayangua.[12] Pentanorcucurbitacins A and B can be extracted withmethanol from the stems ofMomordica charantia.[8] Cucurbitacins B and I, and derivatives of cucurbitacins B, D and E, can be extracted with methanol from dried tubers ofHemsleya endecaphylla.[9]
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 becamesick, involvingnausea,vomiting, anddiarrhea, and had hair loss weeks later.[19] Another French study of poisoning from bittersquash consumption found similar acute illnesses and no deaths.[20] The high concentration of toxin in the plants could result fromcross-pollination[21] with wild cucurbitaceae species, or from plant growth stress due to high temperature anddrought.[22]
^abKapoor S (May 2013). "Cucurbitacin B and its rapidly emerging role in the management of systemic malignancies besides lung carcinomas".Cancer Biotherapy & Radiopharmaceuticals.28 (4): 359.doi:10.1089/cbr.2012.1373.PMID23350897.
^abcdefgChen JC, Zhang GH, Zhang ZQ, Qiu MH, Zheng YT, Yang LM, et al. (January 2008). "Octanorcucurbitane and cucurbitane triterpenoids from the tubers of Hemsleya endecaphylla with HIV-1 inhibitory activity".Journal of Natural Products.71 (1):153–5.doi:10.1021/np0704396.PMID18088099.
^abcWang DC, Pan HY, Deng XM, Xiang H, Gao HY, Cai H, et al. (2007). "Cucurbitane and hexanorcucurbitane glycosides from the fruits of Cucurbita pepo cv dayangua".Journal of Asian Natural Products Research.9 (6–8):525–9.doi:10.1080/10286020600782538.PMID17885839.S2CID27762659.
^Song F, Dai B, Zhang HY, Xie JW, Gu CZ, 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.PMID25761128.S2CID38269788.
^Kusin S, Angert T, von Derau K, Horowitz BZ, Giffin S (2012). "189. Toxic Squash Syndrome: A case series of diarrheal illness following ingestion of bitter squash, 1999-2011". 2012 Annual Meeting of the North American Congress of Clinical Toxicology (NACCT) October 1–6, 2012 las Vegas, NV, USA.Clinical Toxicology.50 (7):574–720.doi:10.3109/15563650.2012.700015.S2CID218859008.
^Le Roux G, Leborgne I, Labadie M, Garnier R, Sinno-Tellier S, Bloch J, et al. (August 2018). "Poisoning by non-edible squash: retrospective series of 353 patients from French Poison Control Centers".Clinical Toxicology.56 (8):790–794.doi:10.1080/15563650.2018.1424891.PMID29323540.S2CID29978562.
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