## 3 Discussion  
In the comparison studies of LPS-induced anti-inflammatory activities and chemical profiles of the SC-CO\({}_{2}\) extract of PFCA versus PFC [19] and the SC-CO\({}_{2}\) versus the ethanol extracts of PFCA [20], the SC-CO\({}_{2}\) extract of PFCA showed greater potency and higher content of **2** and **3** than the SC-CO\({}_{2}\) extract of PFC and the ethanol extract of PFCA. The HPLC chromatogram of these three extracts showed an unknown peak besides the two main peaks for **2** and **3**, and thus it was identified as compound **1**. While, another unknown peak, which appeared in the chromatogram of the SC-CO\({}_{2}\) extract of PFC, but not in the chromatograms of the SC-CO\({}_{2}\) and the ethanol extracts of PFCA, was identified as compound **4**. Therefore, the accumulation of **1-3** and the degradation of **4** in PFCA leaves are thought to be associated with the variation in the metabolic pathways by gamma irradiation effect. The biosynthesis of new compound **1** can be inferred from several studies on the biosynthetic pathway of monoterpene and phenylpropanol proposed from their genetic analysis in _P. frutscens_ (Figure 6) [28; 29; 30; 31]. Compounds **2** and **3** were synthesized from a precursor, geranyl diphosphate (GPP) through the mevalonate pathway. In this reaction, GPP gave rise to a linear monoterpene, geranali (_cis_-citral) by promotion of dominant gene \(G\) which is considered to be essential for the initiation of monoterpene biosynthesis [29]. Geranial (_cis_-citral) was converted to perilene through the furan formation controlled by the polymeric genes (_Fr1_ and _Fr2_) [30] and (or) the oxidation of _cis_-citral controlled by gene \(G\)2, and then the conversion of perilene into egomaketone was promoted by the dominant gene (_J_) that controlled the oxidation of C-6 position of perilene [31]. Based on the construction mechanisms [32], **2** and **3** would be expected to be synthesized by the allylic isomerization and the protonation of alkene, respectively, of the precursor egomaketone. Further hydroxylation of **2** was assumed to create 9-hydroxy-isoegomaketone (**1**) of a new structure type (Figure 6). While, in the absence of gene \(G\), phenylpropanoids accumulated instead of monoterpenes in the perilla plants [28]. Compound **4** was known to be produced in the biosynthesis via the shikimate pathway [32]. Shikimic acid has a role in the formation of aromatic acids, L-phenylalanine, L-tyrosine, and L-tryptophan. Among them, L-phenylalanine generates _trans_-cinnamic acid by the elimination of ammonia from its side-chain via phenylalanine ammonia lyase (PAL) which is an enzyme to catalyze the reaction converting L-phenylalanine to _trans_-cinnamic acid. Deoxidation from _trans_-cinnamic acid generates cinnamyl alcohol, and then eugenol is derived from cinnamyl alcohol by the following steps: loss of hydroxyl as leaving group, resonance form of the allylic cation, and addition of hydride [32]. [PERSON] (2000) suggested that a possible precursor--methyleugenol--was metabolized to compound **4** by the formation of a methylenedioxy group, in the absence of a dominant gene \(E\) which is involved in the production of elemicin. However, to understand the mechanisms responsible for the accumulation of monoterpenes in the gamma-irradiated mutant cultivar PFCA, further enzymological and gene function studies are still necessary. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Peak** & **Compound** & \multicolumn{2}{c}{**Contents (mg/b)**} \\ \cline{3-4}  & & **PFCA** & **PFC** \\ \hline
1 & 9-hydroxy-isoegomaketone (**1**) & 1.33 \(\pm\) 0.07 & 0.15 \(\pm\) 0.02 \\
2 & isoegomaketone (**2**) & 2.76 \(\pm\) 0.05 & 0.51 \(\pm\) 0.02 \\
3 & perillak ketone (**3**) & 6.96 \(\pm\) 0.17 & 1.71 \(\pm\) 0.12 \\
4 & myristcin (**4**) & 0.02 \(\pm\) 0.003 & 36.77 \(\pm\) 5.60 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The contents of compounds in the leaves of PFCA and PFC.