## 2 Results and Discussion  
Yield Percentage and Analysis of the Volatile Compounds from the Rhizome of E. paviaena Essential Oils (EOEP)  
The EOEP obtained after hydrodistillation shows a light yellow color. The yield percentage of EOEP was 0.13% (_v/w_ on fresh weight basis), which is slightly lower than the products obtained from other rhizomes of _Etlingera_ spp., which range between 0.28 and 0.70% (_v/w_ on dry weight basis) [2; 8]. However, this is much greater than the estimated oil yield on a fresh weight basis, which is at 0.019-0.047% (_v/w_) [9]. The volatile composition of the EOEP from rhizome is shown in Table 1. Twenty-two compounds have been identified, representing 99.94% of the total oil composition. This amount comprised  
Figure 1: Photographs of _Etlingera paviaena_ (Pierre ex Gagnep.) R.M.Sm. plant **(A)** and _E. paviaena_ rhizome **(B)**. 2 phenylpropanoids (97.90%), 11 monoterpenes (1.55%), 7 oxygenated monoterpenes (0.40%) and 2 sesquiterpenes (0.09%), respectively. _Trans_-anethole (78.54%) and methyl chavicol or estragole (19.36%) were the major compounds (Figure 2), followed by \(\beta\)-myrcene (0.84%), camphene (0.17%), pinocarvone (0.15%), camphor (0.12%) and \(\alpha\)-pinene (0.12%), respectively. This result is in accordance with [PERSON] and [PERSON] [10], who reported that phenylpropanoids (non-terpemic compounds) were the main chemical group in the rhizome essential oils of the _E. paviaema_, _Etlingera previlabrum_ ([PERSON]) R.M.Sm., _Etlingera cewuga_ ([PERSON].) R.M.Sm., _Etlingera linguiforme_ ([PERSON].) R.M.Sm., _Etlingera litoralis_ ([PERSON]) [PERSON] and _Etlingera puuica_ ([PERSON].) R.M.Sm. Among the phenylproponoids, _trans_-anethole (48.6%) was the major compounds in the essential oil of _E. paviaema_, and methyl chavicol dominated the rhizome oil of _E. p\(\it{\ddot{pu}}\)nica_ (95.75%) and _E. linguiforme_ (49.9%), respectively [2; 11; 12]. In the work of [PERSON] [2], who analyzed the hydrodistilled essential oil from dried rhizomes of _E. p\(\it{\ddot{p}}\)vienna_ in the Chantaburi province, Thailand, trans-anethole (48.6%), \(p\)-anisaldehyde (13.8%), \(\delta\)-cadinene (7.2%), _trans_-methyl isoeugenol (2.7%) and \(\alpha\)-cadinol (2.4%) were the major components. Furthermore, a series of phenylpropanoids, such as 4-methoxycinnamaldehyde, 4-methoxycinnamyl \(p\)-cumarate, 4-methoxycinnamyl alcohol and \(p\)-cumaric acid, have been extracted from the rhizome of _E. p\(\it{\ddot{p}}\)vienna_ from Thailand [3; 5]. In addition, terpen (monoterpene hydrocarbons and sesquiterpene hydrocarbons) and terpenoids (oxygenated monoterpenes and oxygenated sesquiterpenes) were found in small proportions in the essential oil of _E. p\(\it{\ddot{p}}\)vienna_[2; 10]. However, those terpinic compounds are abundant in most _Etlingera_ species, including _E. brevilabrum_, _Etlingera elator_ ([PERSON]) R.M.Sm., _Etlingera f\(\it{\ddot{m}}\)briobracteata_ ([PERSON].) R.M.Sm., _E. megalocheilos_ ([PERSON].) [PERSON], comb. nov. and _Etlingera s\(\it{\ddot{o}}\)vapensis_ [PERSON] and [PERSON] [8; 13; 14; 15; 16]. Monoterpene hydrocarbons, such as \(\alpha\)-pinene, camphene, \(\beta\)-myrcene, d-Limonene and \(\beta\)-ocimene, were found in high percentages in the essential oil, in particular, in the oils from leaves [10; 12; 13]. Comparing the components of essential oils from _Etlingera_ species, the chemical compositions are influenced by the plant species and parts, sources and the methods of preparation [13; 17].