## 3 Factors Influencing PSMs Production in Plants
### Effects of Ozone on PSMs
Fisetin showed numerous biological activities such as protection against cell death from oxidative stress, growth, and maintenance of nerve cells (primary cortical neurons from a rat) [248; 255]. Fisetin suppresses many inflammatory pathways, including Nuclear Factor-kappaB B (NF-kB) pathway, helping prevent cancerous growth [256; 257]. Similarly, [PERSON] et al. [258] also observed the protective effect of fisetin against smoke-induced oxidative stress and inflammation in rat lungs. Plant UV filters, kaempfer, and quercetin are a few other examples of bioactive flavonoids. Kaempfer is an anti-inflammatory [259], chemo-protective [260], and cardio-protective [261]. Polyphenolic resveratrol is one of the essential stilbene phytoalexin produced by a plant's defense mechanism, and it possesses antioxidant, anticancer, and anti-estrogenic properties [262]. The immunohistochemistry compound, calycopterin isolated from the medicinal plant _Dracocephalum kotschvi_[168], was elevated upon UV irradiation in _Gnaphalium luteo-album_[167]. Tanshinones are other examples of bioactive phenols. In response to severe drought stress, their concentration in the _Salvia miltiorrhiza_ increases, including tanshinone I and tanshinone IIA by 182% and 322%, respectively, compared to 148% under the moderate drought stress [139]. Tanshinones are known for their anti-inflammatory, antioxidant, and anticancer properties [263]. Nitrogen-containing compounds, alkaloids, are another group of secondary metabolites widely produced in plants for defense, and they are known to exhibit diverse biological activities, including anti-inflammatory, anti-malarial, and anticancer activities [264]. The fungistatic activity of \(\alpha\)-tomatine (_Solanum_ and _Lycopersicon_ species) in _Fusarium oxysporum_ f. _Iyopersici_ (tomato wilt) was the first bioactive alkaloid reported in 1945 by [PERSON] et al. [69]. Alkaloids and their precursors accumulate more in plants when exposed to various stress factors. For example, _Catharanthus roseus_, when exposed to UV-B radiation, synthesizes more indole alkaloids and precursors of vinblastine and vincristine increase in hairy roots [265]. These alkaloids inhibit cell mitosis by destroying microtubules of the mitotic apparatus, blocking cancer cell division [266]. Bioactive alkaloids accumulate in response to high temperature, drought, and UV-B stresses (Table 1). Indole alkaloid viudoline from _Catharanthus roseus_ (which increases in response to UV-B) showed anti-diabetic (reduces fasting blood glucose level) and anti-inflammatory (reduces pro-inflammatory cytokines, TNF- \(\alpha\) and IL-6) properties [99]. The number of structurally determined specialized plant terpenes exceeds 105, including \(>\)12,000 diterpenoids [267]. Plant terpenids are diverse and have been a valuable source of medicinal discoveries because terpenoids are natural NF-kB signaling inhibitors with anti-inflammatory and anti-cancer properties [268]. Examples include monoterpenes (e.g., \((-)\)-menthol and cannabinoids); sesquiterpenenes (e.g., artemisinin and thapsigargin); diterpenes (e.g., paclitaxel and ingenol mebutate) and triterpenes found in floral and vegetative parts; triterpenoids; and carotenoids (e.g., steroidal alkaloids, cardenolides, and bixin) (Figure 7). Other compounds are partially derived from a terpene precursor, such as monotorepenoid alkaloids (e.g., strychnine), which are synthesized in part from secologanin (Figure 7), a member of the widespread class of iridoid monoterpenes [269]. Figure 7: _Cont._