# Biosynthesis of Phytocannabinoids and Structural Insights: A Review
## 4 Biosynthesis and Pathway of Phytocannabinoids  
Phytocannabinoids are stored in glandular trichomes, located all over the aerial part of the plant; the root surface and root tissue do not produce phytocannabinoids [34]. Moreover, plants grown outdoors are exposed to a fair amount of ultraviolet UV-A and UV-B, and exposure to UV rays before harvest causes the plant to produce more THC compounds [35]. Adaptive responses to changing UV-B conditions also play an important role in plant-herbivore interactions. UVB-mediated changes in plant architecture, physiology, and/or chemistry can alter herbivorous arthropods' performance and preference. In most cases, these UV-B-mediated induced physiological changes lead to the reinforcement of plant defenses. For example, increased production of UV-B-protective secondary metabolites and/or the reinforcement of plant cell walls induced by UV-B was proposed to affect plant colonization by herbivorous arthropods [35]. The pathways are split between different cell types and organelles, the cytoplasm of the gland cells, plastics, and storage of the extracellular cavity [12]. Many cannabinoids are formed in correlation with increased moisture, heat, temperature, and abiotic stress conditions, as well as low soil moisture content. The study demonstrated the potential of mineral nutrition to regulate cannabinoid metabolism and optimize the pharmacological quality of potassium, an essential plant nutrient that is required by plants in relatively high amounts and takes part in many key physiological processes [30]. Processes affected by K supply include stomatal regulation, protein synthesis, photosynthesis, enzyme activation, osmoregulation, and the uptake and accumulation of other essential cations such as Ca and Mg [36]. In addition to its involvement in the regulation of plant primary metabolism, K is known to have a considerable impact on the secondary metabolism of plants and is therefore considered a quality element [35]. As K is known to affect a wide range of secondary metabolites in plants, including phenolic compounds, flavonoids, carotenoids, and organic acids, we hypothesized that it has the potential to regulate the production of medical compounds in _C. sativa_[36]. UV rays at  
Figure 1: Structure of phytocannabinoids. 320 nm provide an evolutionary benefit by acting as sunlight to flowering plants, thus resulting in the production of a greater number of phytocannabinoidss conveying different biological benefits and activities; this represents a crucial light signal to which plants can respond and develop specific photomorphogenic responses [37; 38]. Among these responses, changes in the morphology, physiology, and production of secondary metabolites are commonly described. The main psychoactive constituent in cannabis is THC, and the main non-psychoactive compound is CBD, which accumulates in glandular trichomes and is obtained from plant tissue, flowers, and a high density of plant constituents [38]. The cannabinoid pathways involve the hexanoyl-CoA produced by an acyl-activating enzyme (CsAAE1) derived from hexanoic acid through the fatty acid biosynthesis pathway [39]. Hereafter, type III polyketide synthase Olivetol synthase elongates toward hexanoyl-CoA using three units of malonyl-CoA and has characteristics of another type III polyketide synthase (PKSs) in flowering plants; this method of production requires significant resources and is an unsustainable avenue for harvesting cannabinoidss, given its recent rapid expansion in demand worldwide [40]. Instead, another enzyme, Olivetolic acid cyclase (OAC), catalyzes the necessary C\({}_{2}\) to C\({}_{7}\) aldol condensation reaction to produce olivetolic acid (OLA) (Table 1).