## 4 _Cucurbita_ Plants Phytochemical Composition
### Terpenoids, Saponins and Sterols in Cucurbita  
[PERSON] et al. [55] have demonstrated the existence of calotropoleanly ester and cholesterol in _C. pepo_ fruit, and [PERSON] et al. [62] also represented the cholesterol content in seeds (\(<\)0.2 to 3 mg/100 g). These plant parts were also reported as containing more \(\beta\)-sitosterol (383.89 mg/kg fresh weight) than those of _C. moschata_ and _C. maxima_ (277.58 mg/kg and 235.16 mg/kg fresh weight, respectively) [53]. [PERSON] et al. [93] have reported that, besides cucurbitacins, a new triterpen saponin, foetidissimoside A (3,28-bidesmoxidic triterpen saponin) is also present in C. _foetidissima_ roots. Ten years later, [PERSON] et al. [94] discovered the foetidissimoside B in the same source. Also, [PERSON] et al. [95] extracted sterols from seeds, and the most abundant were \(\Delta\)7.22.25-stigmastatrienol, \(\beta\)-sitosterol, spinasterol and \(\Delta\)7.25-stigmastadienol [61]. Cucurbitacin is a triterpenoid [96] with a bitter taste, isolated from members of the Cucurbitaceae family, and there are more than 18 types of cucurbitacin in the nature. Cucurbitacins are a group of distinctive highly oxygenated triterpen substances, having tetracyclic triterpenes with a cucurbitane skeleton. Figure 1 details the structure of 19-(10\(\rightarrow\)9\(\beta\))-abeo-10\(\alpha\)-lanost-5-ene. They are cucurbitane triterpenes with double bonds between C4 and C5, a hydroxyl at C16, C20 and C25 and a ketone at C11 and C22 [20]. These compounds are well-recognized for their bitterness and toxicity [97]. Cucurbitacins are randomly divided into 12 groups, specifically cucurbitacins A-T, varying in their oxygen functionalities at different positions. The chemical structures of a few cucurbitacins (A, B, C, and D) are presented in Figure 2, and the cucurbitacin composition in different _Cucurbita_ species is summarized in Table 5.  
Figure 1: Principal structure of cucurbitacins (19-(10\(\rightarrow\)9\(\beta\))-abeo-10\(\alpha\)-lanost-5-ene). Seedlings of the pumpkin _C. maxima_ have been reported to involve high amounts of cucurbitacin B and small amounts of cucurbitacin D and E in radicles and cotyledons [98]. Eighteen _Cucurbita_ plants species were analyzed for their cucurbitacin contents. Bitter species having comparatively high contents of cucurbitacins B and D and no detectable cucurbitacins E and I were identified as _Cucurbita andreana_ [PERSON], _Cucurbita ecuadorensis_ [PERSON], _Cucurbita radicans_ [PERSON], _Cucurbita lundelliana_ [PERSON], _C. argyrosperma_ and _Cucurbita pedatifolia_ [PERSON]. The other group of wild, bitter species having relatively large amounts of cucurbitacins E and I were _Cucurbita cylindrata_ [PERSON], _C. foetidissima_, _C. martinezi_, _C. okeechobeensis_, and _Cucurbita palmata_ [PERSON], _Cucurbita pepo_ var. _texana ([PERSON]) D.S.Decker_ was found to contain nearly all cucurbitacins as cucurbitacin E-glycoside. However, no cucurbitacin could be identified in domesticated and sweet species, including _C. ficifolia_, _C. maxima_, _C. moschata_, and _C. pepo_[48]. The same group of investigators also determined the cucurbitacin and cucurbitacin glycoside content in fruits of two _Cucurbita_ plant hybrids (_C. andreana_\(\times\)_C. maxima_ and _C. texana_\(\times\)_C. pepo_), as well as in _C. foetidissima_ roots. As a result, _C. andreana_\(\times\)_C. maxima_ fruits contained cucurbitacins B and D, whereas _C. texana_\(\times\)_C. pepo_ fruits and _C. foetidissima_ roots presented cucurbitacins E and I [99]. With regards to _C. andreana_ fruits extract, it was chromatographically fractionated, and cucurbitacins B, D, E and I, as well as cucurbitacin E and I aglycones and cucurbitacin B, E, and I glucosides were detected in this species [102]. _C. pepo_ comprises the most investigated _Cucurbita_ plant for its cucurbitacin content. In an earlier study, cucurbitacin E was detected as a primary bitter component in seedling _C. pepo_ radicles, whereas cucurbitacins B and I were found in trace amounts in the same tissue.