# _Thuja occidentalis_ L. (Cupressaceae): Ethnobotany, Phytochemistry and Biological Activity
## 3 Phytochemistry  
The chemical composition of the _Thuja occidentalis_ is summarized in Table 2.  
The fresh plant contains approximately 0.6% essential oil (EO), 2.07% reducing sugars, 4.9% polysaccharides, 2.11% minerals, 1.67% free acids, and 1.31% tannic agents [68]. The main monoterpenes identified in the EO obtained from fresh leaves are 65% thujone, 8% isothujone, 8% fenchone, 5% subines, and 2% \(\alpha\)-pinene [68]. Other identified monoterpenes are: carvotanacetone, origanol, origanes, myrcen, and camphen [68; 69; 70; 71]. Moreover, high molecular weight glycoproteins or polysaccharides have been shown to be particularly relevant for plant activity [72]. \begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{2}{c}{**Chemical Composition of the Fresh Plant**} \\ \hline Essential oil (\(v\)/\(w\)) & \\ Essential oil compounds (mainly monoterpenes): & \\ thujone (65%); isothujone (8%); fenchone (8\%); & 0.6\% \\ sabines (5%); \(\alpha\)-pinene (2\%) & \\ Reducing sugar & 2.07\% \\ Minerals & 2.11\% \\ Free acids & 1.67\% \\ Tannic agents & 1.31\% \\ \hline \multicolumn{2}{c}{**The Constituents of the Dried Herbal Substance (Thuja occidentalis Herbal)**} \\ \hline  & Bornel \\  & Camphene \\  & Fenchone \\  & Limonene \\ Essential oil & Myricene \\  & \(\alpha\)-Terpine \\  & Terpinolene \\  & Thujone (85\% \(\alpha\)-thujone and 15\% \(\beta\)-thujone) is the \\  & main compound (0.76–2.4\%) \\ \hline  & \(p\)-Couramic acid \\  & Umbelliferone \\ \hline  & Kaempferol \\  & Kaempferol-3-O-\(\alpha\)-rhammoside \\  & Mearnstirin \\ Flavonoids & Myricetine \\  & Myricitin \\  & Quercetin \\  & Quercitrin \\ \hline  & Catechine \\ Tannins & Gallocatechine \\ \hline  & Proyanidin B-3 \\ Proanthocyanidines & Prodelphinidin \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The chemical composition of the fresh and dried _T. occidentalis_. The dry plant has 1.4-4% EO, whose constituents are borneol, camphene, fenchone, limonene, myricene, \(\alpha\)-terpine, terpinolene, thujone, thuijlalcohol. Thujone consists of 85% \(\alpha\)-thujone and 15% \(\beta\)-thujone is the main compound (0.76-2.4%) found in the EO obtained from the dry plant. Other compounds present in the dry plant are coumarins, represented by \(p\)-coumaric acid and umbelliferone; flavonoids, e.g., kaempferol, kaempferol-3-\(O\)-\(\alpha\)-rhammoside, mearnistrin, myricetin, myricitin, quercetin, and quercetin; and tannins, (+/-)-catechins, (-)-gallocatechin, and proanthocyanidines, like pocyanidin B-3 and prodelphinidin. Other constituents are tannic acid, which is about 1.3%, as well as polysaccharides and proteins representing approximately 4% [58; 68; 73; 74; 75; 76; 77; 78]. [PERSON] et al. (2016) have found that the _T. occidentalis_ leaf methanolic extract contains 135.32 mg/g total polyphenols expressed in gallic acid equivalent and 3.46 mg/g of total flavonoids expressed in quercetin equivalent [36]. Thujone is the monoterepne found in the composition of many plants including _Thuja occidentalis_. However, the use of this compound is regulated by the European Parliament and Council and the European Medicines Agency [67]. The isomers \(\alpha\)-thujone and \(\beta\)-thujone are monoterepne ketones, with the following IUPAC name: (15,4,5,5)-4-methyl-1-(propane-2-yl) bicyclo (3.1.0) hexan-3-one [67]. In a previous study, we found, in an ethanolic extract made from fresh leaves, 21.13 \(\upmu\)g/mL thujone, 2.16 mg/mL total phenolic acids expressed in caffeic acid, 0.36 mg/mL total flavonoids expressed in rutoside, respectively [37]. However, to date, the genetic regulation of thujone synthesis pathway has been studied in two species: _Salvia officinalis_ and _Thuja placata_. Geranyldiphosphate (GPP) and nervl-diphosphate are the general precursors' starting points and follow a four-step pathway. Sabinene is the first monoterepne in this path, being catalyzed by the enzyme sabinene-synthas (SS). It has been showed that sabinene is the precursor of thujone in _S. officinalis_, _A. absinthium_, and _T. vulgare_.