## 4 _Cucurbita_ Plants Phytochemical Composition
### Phenolic Compounds in Cucurbita
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Compound Name** & **Synonym(s)** & **Empirical Formula** & **Structure** \\ \hline
**Protocatechuic acid** & 3,4-Dibydroxyleneoic acid & C\({}_{7}\)H\({}_{6}\)O\({}_{4}\) & \\ \hline p-Hydroxybenzoic acid & 4-Hydroxybenzoic acid & C\({}_{7}\)H\({}_{6}\)O\({}_{3}\) & \\ \hline p-Hydroxybenzoic acid & 4-Hydroxybenzoic acid & C\({}_{7}\)H\({}_{6}\)O\({}_{3}\) & \\ \hline p-Hydroxybenzoicaldehyde & 4-Hydroxybenzoicaldehyde & C\({}_{7}\)H\({}_{6}\)O\({}_{2}\) & \\ \hline
**Vanillic acid** & 4-Hydroxy-3-methoxybenzoic acid; p-Vanillic acid & C\({}_{8}\)H\({}_{6}\)O\({}_{4}\) & \\ \hline
**Caffeic acid** & 3,4-Dibydroxyleneomic acid & C\({}_{9}\)H\({}_{6}\)O\({}_{4}\) & \\ \hline
**Syringic acid** & 3,5-Dimethoxy-4-hydroxybenzoic acid & C\({}_{8}\)H\({}_{20}\)O\({}_{5}\) & \\ \hline
**Trans-p-coumaric acid** & trans-4-Hydroxycinamic acid & C\({}_{9}\)H\({}_{6}\)O\({}_{3}\) & \\ \hline
**Ferulic acid** & 3-Methoxy-4-Hydroxycinamic acid; & C\({}_{10}\)H\({}_{10}\)O\({}_{4}\) & \\ \hline
**FA study by [PERSON] et al. [84] showed no flavonoid content (detection limit: 0.05 mg/100 g) in either the immature or mature fruits of _C. maxima_. Only the shoots and buds showed positive results. However, in accordance with [85], the total flavonoid and phenolic contents of this species were determined as approximately 2.7 mg quercetin equivalent/g extract and 8.8 mg gallic acid equivalent (GAE)/g extract, respectively. [PERSON] and [PERSON] [86] reported that average total phenolic content of _C. maxima_ was 46.43 mg GAE/100 g. In another study, _C. maxima_ was analyzed for its flavonoid content, and kaempfer was found to be the only flavonoid present in this species at a concentration of 371.0 mg/kg of dry weight [87]. _C. pepo_ was also found to have low polyphenol content. However, [PERSON] et al. [88] have reported for the first time a list of 34 polyphenols, including a variety of flavonoids in the _C. pepo_ fruit, in addition to other unknown polar compounds. Also, the _C. pepo_ flowers may contain considerable amounts of phenolic compounds. A total polyphenol content ranging from 0.054 to 0.297 g GAE/ug dry biomass has been reported to be dependent on the extraction conditions and flower sex [89]. [PERSON] et al. [90] studied the phenolic content of six pumpkin (_C. pepo_) seed oils and identified the following compounds: tyrosol, luteolin, ferulic acid, vanillic acid, and vanillin. Among them, tyrosol was the most abundant compound, ranging from 1.58 mg/kg to 17.69 mg/kg. Five major compounds in _C. ficifolia_ fruit aqueous extract were identified by [PERSON] et al. [91] as: _p_-coumaric acid, _p_-hydroxybenzoic acid, salicin, stigmast-7,2,2-dien-3-ol and stigmast-7-en-3-ol. On the other hand, [PERSON] et al. [92] assessed the phenolic acids content of _C. pepo_ seeds. _p_-Hydroxybenzoic acid was found to be the prevailing phenolic acid, with 34.72%, 51.80%, and 67.38% of the total phenolic acids content in whole dehulled seed, hulls, and kernels, respectively. Aside from _p_-hydroxybenzoic acid, the most dominant phenolic substances can be listed in a decreasing order of quantity as