## 3 Results and Discussion
### Extraction, Color, and Yield of C. japonica Leaf EO
#### 3.1.2 Comparison to Previous Studies on _C. japonica_ Leaf EO Isolated by HD  
The HD method, using a Clevenger-type apparatus, is the mostly commonly used to obtain _C. japonica_ leaf EO at a laboratory scale due to its simplicity and efficient EO extraction, as demonstrated in this study. Table 2 shows data from the literature on the yield and color of EO-HD samples from leaves of red heartwood-type _C. japonica_ according to geographic region, for comparative purposes. Other relevant data are summarized in Table 2, namely plant age; harvest period; status of the plant material (fresh or dry) before the distillation process; and HD conditions, such as solute-to-solvent ratio and distillation time (DT). \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Distillation Method**} & \multicolumn{2}{c}{**Essential Oil**} \\ \cline{2-3}  & **Yield (\%, _v/w_)**1 ** & **Color** \\ \hline Hydrodistillation (HD) & 1.21 \(\pm\) 0.03 2 & Pale yellow \\ Water-steam distillation (WSD) & 0.45 \(\pm\) 0.01 2 & Colorless \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Yield and color of the essential oil of Azorca _Cryptomeria japonica_ fresh leaves, isolated by two distillation methods (HD and WST). The results on the leaf EO-HD yield of _C. japonica_ samples from different origins revealed that the yield obtained in the present study (1.21%, _v/w_, FW) is within the range reported in the literature (Table 2), being higher than that observed in two Korean samples (0.6% and 0.84%, _v/w_, FW) [25, 27], respectively. As also observed in Table 2, [PERSON] et al. [15] reported a significantly higher yield (4.7%, _w/w_, dry weight) for a Korean sample that, however, was distillated over 24 h [15] (an unusual DT). In fact, the majority of the referenced studies used a DT that ranged between 2 and 6 h, with 4 h or 6 h being the predominant distillation period (Table 2). The differences observed on the leaf EO yield from _C. japonica_ plant can be due to the impact of different factors, namely genetic background of the plant, plant age, vegetative cycle stage, region and altitude where it is grown, environmental parameters variations, sampling time, processing and storage practices, and HD conditions (e.g., solute-to-solvent ratio and DT). Furthermore, it should be highlighted that a comparison of the yield data between different studies is very difficult when information about the plant material and the extraction protocol is incomplete and/or different units of measurement are used, as demonstrated in the data from literature presented in Table 2. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline _C. japonica_ & **Pant Age** & **Harvested** & **Leaves** & \multicolumn{3}{c}{**Eo Isolated by HD 2**} & \\ _Origin_ & **(years)** & **Time** & **Status** & \multicolumn{3}{c}{**Using a Clevenger-Type**} & \\ \cline{5-8}  & & & & **DT** & **Yield** & **Color** & \\ \hline São Miguel Island & & & & & & & \\ (Azores) 1  & 30–40 & Nov. 2016 & fresh & 3 h & 1.21\% (_v/w_) & pale yellow & - \\ Faial Island & & & & & & 0.5–0.8\% & - & [11] \\ (Azores) & & & & & & & \\ \hline Corsica Island & & & & & & & \\ (France) & & & & & & & \\ \hline Yakushima Island & & & & & & & \\ (Japan) & & & & & & & \\ \hline Hefei & & & & & & & \\ (China) & & & & & & & \\ \hline Bagmati Zone & & & & & & & \\ (Nepal) & & & & & & & \\ \hline Jeju Island & & & & & & & \\ (South Korea) & & & & & & & \\ \hline \multirow{3}{*}{Nantou County (Central Taiwan)} & 58 & & & & & 2.37\% (_w/w_; DW) & \multirow{3}{*}{—} & [36] \\  & 42 & & & & & 1.91\% (_w/w_; DW) & \multirow{3}{*}{—} & [33] \\  & 26 & & & & & 2.19\% (_w/w_; DW) & \\ \hline Nantou County (Central Taiwan) & 28 & August & & & & & \\ \hline \multirow{3}{*}{(Central Taiwan)} & \multirow{3}{*}{24} & \multirow{3}{*}{2009} & \multirow{3}{*}{ fresh} & \multirow{3}{*}{6 h} & \multirow{3}{*}{1.60\% (_w/w_; DW)} & \multirow{3}{*}{—} & [33] \\  & & & & & & \\ \hline \end{tabular}
\end{table}