## 3 Results and Discussion
### Essential Oils Characterization by Gas Chromatography-Mass Spectrometry (GC-MS)  
The essential oils herein studied were chemically characterized through GC-MS to establish the volatiles profiles of each sample and identification of major compounds. The GC-MS analysis of the _Cymbopogon citratus_ EO (Table 1) revealed the presence of \(\alpha\)-citral (38.5%) and neral (30.8%) as major volatiles, followed by other compounds like \(\beta\)-myrce(17.2%) and geraniol (6.2%). In fact, citral comprises a mixture of two isomeric forms: the geranial (\(\alpha\)-citral), which is the _trans_ isomeric form; and neral (\(\beta\)-citral), which corresponds to the _cis_ isomeric structure [80]. The herein determined major volatiles are frequently assumed as major compounds in the essential oil of _C. citratus_, and are in accordance with previous reports [81,82]. \begin{table}
\begin{tabular}{l c c c c} \hline \hline \multirow{2}{*}{**Identified Compound**} & **R.T.** & \multirow{2}{*}{**RI\({}_{\text{exp}}\)**} & \multirow{2}{*}{**RI\({}_{\text{lit}}\)**} & \multicolumn{2}{c}{**Percentage in**} \\  & **(min)** & & & **C.** _citratus_ \\ \hline \(6\)-Methyl-\(5\)-hepten-\(2\)-one & 10.17 & 977 & 985 & 0.8 \\ \hline \(\beta\)**-Myrence** & **10.33** & **982** & **989** & **17.2** \\ \hline _cis-\(\beta\)_-Oximene & 12.39 & 1032 & 1038 & 0.2 \\ \hline _trans-\(\beta\)_-Oximene & 12.85 & 1043 & 1048 & 0.1 \\ \hline n.d. & 14.89 & & & 0.1 \\ \hline \(3\)-Methyl-\(2\)-(\(2\)-methyl-\(2\)-butenyl)-furan & 15.08 & 1098 & 1095 & 0.2 \\ \hline Linalool & 15.18 & 1101 & 1101 & 0.9 \\ \hline n.d. & 15.19 & & & 0.2 \\ \hline n.d. & 17.28 & & & 0.1 \\ \hline n.d. & 17.46 & & & 0.1 \\ \hline Citronellal & 17.66 & 1162 & 1165 & 0.1 \\ \hline n.d. & 18.21 & & & 1.0 \\ \hline Rosefuran oxide & 18.71 & 1187 & 1176 & 0.1 \\ \hline Isoneral & 19.05 & 1196 & 1185 & 1.6 \\ \hline Citronellol & 21.12 & 1247 & 1240 & 0.3 \\ \hline n.d. & 21.35 & & & 0.1 \\ \hline _cis-Citral_ & **21.70** & **1261** & **1249** & **30.8** \\ \hline _trans-Geraniol_ & **22.31** & **1275** & **1258** & **6.2** \\ \hline _trans-Citral_ & **23.07** & **1293** & **1271** & **38.5** \\ \hline \(2\)-Undecanone & 24.08 & 1319 & 1302 & 0.2 \\ \hline Neric acid & 26.67 & 1383 & 1347 & 0.1 \\ \hline Nerol acetate & 28.00 & 1415 & 1386 & 0.7 \\ \hline Caryophyllene & 29.40 & 1449 & 1444 & 0.1 \\ \hline \(2\)-Tridecanone & 32.59 & 1528 & 1499 & 0.1 \\ \hline Caryophyllene oxide & 35.90 & 1610 & 1613 & 0.1 \\ \hline n.d. & 37.26 & & & 0.1 \\ \hline
**Total identified compounds (\%)** & & & & **98.3** \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Identification, retention time (min) and relative amounts (%) of compounds in the essential oil of _Cymbopogon citratus_. Results are expressed as average percentage (%) of peak area \(\pm\) standard deviation (\(n\) = 3). Compounds are listed in order of elution from the HP-5 MS column. Major compounds are presented in bold. Abbreviations: n.d.: not determined, which means compounds that were not identified in the studied samples; R.T.: retention time of the eluted compounds expressed in minutes; RI\({}_{\text{exp}}\): experimental retention index calculated relative to n-alkanes series standards (C7–C30) on the HP-5 MS column; RI\({}_{\text{lit}}\): literature retention index on the similar phase column. RI\({}_{\text{exp}}\) and RI\({}_{\text{lit}}\) values associated with “-” were unable to be determined. Focusing on the assessed samples from genus _Menttha_, these plants are frequently referred to by their complicated taxonomic rearrangement, given the natural occurrence of several genotypes and phenotypes, plus the high degree of chemical variability among the essential oils obtained from these plants. This variability is mostly attributed to the ontogeny state of the harvested plants, cultivation regimens, plant organs used for essential oil isolation, geographic and edaphoclimatic conditions and frequent hybridization between different mint species [83].