## 2 Results
### Analysis of Essential Oil Compositions
2, 3, 10, 11, 20, 25, 28, 32, 40, 56, 58, 61, 68, 69, 73) & & 24.1 & 8.0 \\ Benzenes (Sr. No. 6, 9, 12, 14, 16, 18, 19, 23, 24, 54) & & & 7.5 & 18.8 \\ Alcohols (Sr. No. 4, 5, 8, 15, 52, 66, 67) & & & & 34.1 & 3.5 \\ Aldehydes (Sr. No. 1, 7, 17 Table 1 and Figure 2a showed a comparison of the number and relative amount between the leaf and stem volatiles compounds in _F. japonicum_, demonstrating that the types of chemical compound from the extracts of different plant parts could vary greatly. In total, 47 essential compounds were found in the leaf volatiles, containing 15 terpenoids, 7 hydrocarbons, 6 alcohols, 5 benzenes, 2 aldehydes, 2 esters, 2 phenolics, 2 fatty acids, 1 ketone, 1 steroid, and 1 coumarin. However, 40 essential compounds found in the leaf volatiles were identified including 9 hydrocarbons, 8 benzenes, 8 terpenoids, 3 esters, 3 phenolics, 3 fatty acids, 2 alcohols, 2 ketones, 2 steroids, and 1 aldehyde. The relative amounts of different volatiles, as shown in Table 1 and Figure 2b, also revealed a significant difference between the leaf and stem. The compounds type in leaf oil mainly included alcohols (34.1%), hydrocarbons (24.1%), terpenoids (16.2%), benzenes (7.5%), and fatty acids (4.9%). In contrast, the stem oil was dominated by benzenes (18.8%), ketones (13.9%), terpenoids (17.0%), fatty acids (8.8%), phenolics (8.7%), steroids (8.6%), hydrocarbons (8.0%), and esters (5.7%). The compounds were mainly separated into five classes in leaf oil, while the stem contained eight classes. This could be due to significant constituent diversity in the stem due to different secondary metabolism processes. This might explain why the leaf and stem oils have significantly different flavors. The main classification of _F. japonicum_ flower volatile compounds found was hydrocarbons in a previous study, including carophyllene, 1-undecene, and 1-nonene [1]. This differed from the volatile compounds found in the _F. japonicum_ leaf and stem in the present  
Figure 2: Comparison of volatile compounds from leaf and stem oils in _F. japonicum_: compounds number (**a**) and relative amounts of volatile compounds (%) (**b**). study. However, two compounds were identified in both studies: cryophyllene oxide, which coexisted in the leaf and flower oil at total ratios of 1.9% and 0.9%, respectively, and diethyl phthalate, which coexisted in the leaf, stem, and flower oil at total ratios of 1.4%, 2.7%, and 1.5%, respectively. The findings also revealed that the flower oil composition of volatiles differed significantly from that of the leaf or stem. The generation of plant volatiles is highly organized based on genetic and ecological diversity at different development stages [16]. As seen in Figure 3, two pathways of producing methyl-D-erythnitol phosphate (MEP), and mexulonic acid (MVA) exist in terpenoid biosynthesis and regulation. This includes a process of converting small plant molecules to complex and diversified structures via related enzymes, including the creation of general precursors, isopentenyl diphosphate (IPP), the double-bonded isomer dimethylallyl diphosphate (DMAPP), the direct precursors geraniol diphosphate (GPP) and farnesyl diphosphate (FPP), and terpenoids [17]. All terpenoids in nature have IPP and DMAPP as their basic synthesis units, further producing direct precursors of GPP, FPP, and geraniol diphosphate under the action of enzymes. GPP and FPP represent the natural shared stage of terpenoids synthesized by plants. Geraniol diphosphate, at the most important stage of terpenoid synthesis, involves a greater amount of terpene synthases and modifying enzymes, and is directly related to varied and complex terpenoids [18; 19; 20]. Enzymes involved in terpenoid biosynthesis that encoded genes expression and regulation are key research domains. There are three main rate-limiting enzymes in the MVA pathway: 3-hydroxy-3-methylglutaryl CoA reductase (HMGR), 5-phosphomevalonate kinase (PMK), and mexulonate kinase (MK).