## 2 Results
### HS-SPME/GC-MS Analysis  
Aromax Ltd.'s lemongrass EO contained 60.6% citral, 34.5% gerani and 26.1% neral. Its minor volatile compounds were cryophyllene-oxide (4.7%), geraniol (4.3%), linalool (2.6%), \(\alpha\)-terpineol (1.7%), \(\gamma\)-cadinene (1.4%) and limonene (1.3%) (Figure 2, Table 2).  
Analysis of Antibacterial Compounds of Lemongrass EO Using Thin-Layer Chromatography Combined with Direct Bioautography  
The TLC-DB method was used to reveal the antibacterial components of lemongrass EO. According to the Rf value, the main component of lemongrass EO was citral. This was also confirmed by the commercial citral control. Based on its Rf value, we could not determine the identity of one characteristic spot. This spot was cut out (Figure 3) and analysed further with a preparative chromatographic method.  
Figure 2: Chromatogram of the HS-SPME/GC-MS analysis of the West Indian lemongrass essential oil (_Cymbopogon citratus_) used in this study obtained from Aromax Ltd. Each compound can be identified based on the data in Table 2 (tR (min)).  
Component Identification with Headspace Solid-Phase Microextraction and Gas Chromatography-Mass Spectrometry (HS-SPME/GC-MS)  
As a result of the HS-SPME/GC-MS analysis of the unidentified cut spot isolated from the TLC-bioautography plate, we were able to distinguish nine characteristic peaks and several minor ones (Figure 4). \(\alpha\)-Terpineol, \(\gamma\)-cadinene and calamenene abundance were 13.2%, 7.0% and 3.7%, respectively.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Name of Compounds** & **tR (min)** & **KI** & **Presence in \%** & \\ \hline  & & & Lemongrass EO & Fraction \\ \hline Camphene & 5.5 & 941 & 0.8 & \\ \hline Limonene & 7.3 & 1023 & 1.3 & \\ \hline Linalool & 8.8 & 1091 & 2.6 & \\ \hline Verbenol & 10.5 & 1171 & 0.4 & \\ \hline \(\alpha\)**-Terpineol** & **10.9** & **1190** & **1.7** & **13.2** \\ \hline Carveol, trans & 11.0 & 1195 & 0.5 & \\ \hline Carveol, cis & 11.4 & 1216 & 1.0 & \\ \hline Neral & 11.8 & 1237 & 26.1 & \\ \hline Geraniol & 12.0 & 1247 & 4.3 & \\ \hline Piperitone & 12.1 & 1253 & 0.6 & \\ \hline Geranial & 12.4 & 1268 & 34.5 & \\ \hline Geranyl formate & 12.8 & 1289 & 0.7 & \\ \hline Neryl acetate & 13.9 & 1350 & 0.7 & \\ \hline \(\beta\)-Caryophyllene & 15.2 & 1424 & 1.0 & \\ \hline \(\Delta\)**Cadinene** & **16.7** & **1513** & **1.4** & **7.0** \\ \hline \(\Delta\)**Calamenene** & **16.9** & **1525** & **0.6** & **3.7** \\ \hline Caryophyllene-oxide & 17.9 & 1588 & 4.7 & \\ \hline Sum & & & 82.2 & \\ \hline M\({}^{+}\)140 & 6.3 & 977 & 0.8 & \\ \hline M\({}^{+}\)155 & 8.2 & 1064 & 0.4 & \\ \hline M\({}^{+}\)152 & 9.7 & 1133 & 0.5 & \\ \hline M+166 & 10.6 & 1176 & 0.6 & \\ \hline M\({}^{+}\)166 & 12.6 & 1279 & 0.4 & \\ \hline M\({}^{+}\)168 & 13.6 & 1333 & 3.2 & \\ \hline M\({}^{+}\)164 & 14.1 & 1361 & 0.4 & \\ \hline M\({}^{+}\)204 & 14.3 & 1372 & 9.8 & \\ \hline M\({}^{+}\)166 & 14.8 & 1400 & 0.6 & \\ \hline M\({}^{+}\)204 & 16.1 & 1475 & 0.7 & \\ \hline Sum & & & 17.4 & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Percentage compound composition of the West Indian lemongrass essential oil (_Cymbopogon citratus_) used in this study. Compounds determined from the outcutted from the TLC-BD plate are labelled with bold.