## 2 Generalities and Classification of Cannabis Metabolites
### Phenolic Compounds of Cannabis  
Phenolic compounds encompass a broad group of specialized metabolites, characterized by a hydroxyl group attached to a benzene ring (phenol). This structural foundation allows for substantial chemical diversity, encompassing, among others, simple phenols, phenolic acids, cinnamic acids, flavonoids, and stilbenes (Table 1). Additionally, this group  
Figure 1: Overview of the primary to specialized metabolic flow in _Cannabis_. Plants synthesize metabolites through photosynthesis, which serves as foundational source for both primary and specialized metabolites. Primary metabolites, produced through essential pathways such as glycolysis, tricarboxylic acid cycle (TCA), shikimate pathway, and urea cycle, provide precursors for specialized metabolite biosynthesis. This diagram highlights key cannabinoids (blue), terpenoids (green), and nitrogen-containing (orange) and phenolic (purple) compound pathways, with examples of metabolites frequently found in _Cannabis_ further detailed in Section 3. A solid arrow represents one enzymatic reaction (bold abbreviation next to it is the name of the enzyme), whereas a dashed arrow indicates sequences of multiple reactions. The figure is adapted from schemes by [PERSON] and [PERSON] (2008) [29]. Abbreviations are found in Appendix A—Tables A1–A5.  
includes complex phenolic polymers like lignans, tannins, and phlobaphenes, which contribute to structural integrity [28]. Various subclasses of phenolic compounds have been identified in _Cannabis_, such as is the case with flavonoids, underscoring the structural and functional diversity within this group [30].  
The roles of phenolic compounds in plants are as diverse as their structures. Their antioxidative properties, for instance, are integral to plant defense, where they capture reactive oxygen species (ROS) to manage cellular ROS such as hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Type** & **Example** & **Structure** \\ \hline Simple phenols & Eugenol & \\ Phenolic acids & Protocatechuic acid & \\ Cinnamic acids & \(p\)-coumaric acid & \\ Flavones & Cannflavin B & \\ Flavanones & Naringenin & \\ Anthocyanins & Cyanidine & \\  & 3-O-rutinoside & \\  & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Classes of phenolic compounds and molecular examples found in _C. sativa_.  
concentrations [31]. Phenolic compounds also protect plants from UV radiation, as exemplified by flavonoids and cannabinoids in _Cannabis_, and they defend against aggression by predators, herbivores, and pathogens. Phenolic compounds are also responsible for several colors found in the plant kingdom; this is particularly the case for the vibrant hues of anthocyanins, a subgroup of flavonoids [12; 31; 32; 33]. Furthermore, phenolic polymers biosynthesized from phenylpropanoids (e.g., lignin, suberin, condensed tannins) provide rigidity and stability to gymnosperms and angiosperms, particularly against mechanical stresses [34], whereas other metabolites also derived from the phenylpropanoid pathway contribute to pathogen resistance, promoting the colonization of new environments [35]. Although phenolic compounds' function is understood in a general sense, all in all, not many studies investigate the roles of _Cannabis_ phenolics in plants.