## 3 Results and Discussion
### GC-MS Analysis of _P. amboinicus_ essential oil Extract
It was suggested in this pathway that the GPP is probably cyclized to \(\gamma\)-terpinene, aromatized into p-cymene, followed by hydroxylation to carvacrol/thymol and thymhydroquinone, and oxidation to TQ [43]. The suggested model was supported by the succession in accumulation of the precursors, such as \(\gamma\)-terpinene, p-cymene, and carvacrol in _N. sativa_ seeds [43]. However, thymo-hydroquinone was not detected in the hexane-extracted samples in this study, but was noted in our previous work using SPME [12]. Based on the abovementioned pathway, it is hypothesized that \(\gamma\)-terpinene might serve as a precursor for p-cymene, whereas p-cymene is a precursor for carvacrol in _N. sativa_, thyme, and oregano [43; 44]. We noticed the same trends in the accumulation of \(\gamma\)-terpinene, p-cymene, carvacrol, and TQ in _P. amboinicus_. This hypothesis was supported by a decrease in \(\gamma\)-terpinene and p-cymene levels in parallel to an increase in carvacrol and TQ (Table 1). Maximum TQ was detected at 2 p.m., and it was observed that a decrease in \(\gamma\)-terpinene and p-cymene was accompanied by an increase in carvacrol and TQ. The minimum amount of TQ (3.31%) was observed at 8 p.m., which coincided with a decrease in carvacrol and increased relative concentrations of \(\gamma\)-terpinene and p-cymene compared to the earlier time points. This trend was in agreement with [PERSON] et al. [45], in which poor content of carvacrol in _O. syriacum_ was accompanied by an increased rate of \(\gamma\)-terpinene and p-cymene. Our finding was also consistent with _O. vulgare_ x _O. majorana_, where \(\gamma\)-terpinene content followed the trend of p-cymene accumulation [46]. Light intensity and temperature are among the factors that could influence the quality and compositions of essential oil in Lamiaceae. Higher light intensity was reported to enhance the relative content of p-cymene in _O. syriacum_, whereas the content of thymol and \(\gamma\)-terpinene generally decreased [47]. Our findings showed an opposite trend, whereby p-cymene and \(\gamma\)-terpinene contents decreased under high light intensity (2 p.m.) and in creased at night (8 p.m.). The same observation was reported by [PERSON] et al. [31] and [PERSON] et al. [48], in which the content of p-cymene increased in _O. vulgarae_ L ssp. _hirtum_ (Link) Ietswaart under reduced light conditions. On the contrary, carvacrol and TQ accumulations were higher during midday and decreased at night, which could be related to the reduced temperature and light conditions. The higher level of carvacrol and thymoquinone in extract harvested at 2 p.m. may explain the increase in TFC and TPC in the sample (Figure 5). It was previously reported that the sudden temperature change in summer and winter seasons caused changes in the biosynthetic pathway, favoring the production of different metabolites such as phenolic compounds rather than essential oil production [49]. However, we were unable to establish a clear trend for this occurrence because the essential oil contents for samples harvested at 8 a.m. and 2 p.m. (Table 1) were comparable, with the highest TPC exhibited in the 2 p.m. extract. Therefore, more studies are necessary to establish a clear correlation between the essential oil content with TPC and TFC in _P. amboinicus_. In the carvacrol chemotype of _Origanum_, higher temperature favors the carvacrol hydroxylase, an enzyme that mediates carvacrol synthesis, leading to the increase in carvacrol and a decrease in p-cymene [50]. According to [PERSON] et al. [31], when the light intensity is reduced, the activity of carvacrol hydroxylase is diminished, resulting in a lower amount of carvacrol being synthesized. It was also reported that the lower activity of carvacrol hydroxylase at cooler temperature resulted in the accumulation of p-cymene due to a bottleneck situation for the subsequent biosynthesis step [50].