# Antinociceptive Effect of an Aqueous Extract and Essential Oil from _Baccharis heterophylla_
## 2 Results and Discussion
### Volatile Composition Analyses  
The volatile components profile of _B. heterophylla_ was gathered by gas chromatography-mass spectrometry (GC-MS) analyses of EO obtained by hydrodistillation and head space-solid phase microextraction (HS-SPME)-adsorbed compounds. The HS-SPME is a more efficient, quicker, and free-solvent method for analyzing volatile constituents from plants and other matrices [30]. The results of the study of EO are summarized in Table 1 and Figure 3. The EO of _B. heterophylla_ is characterized by a high concentration of monoterpenes, such as \(\beta\)-pinene (28.86%), myrcene (29.57%), and D-limonene (36.24%). These results agree with the chemical composition of essential oils reported for other species of the genus _Baccharis_[31]. For the HS-SPME analysis, four fibers were employed, carboxen/polydimethylsiloxane (CAR/PDMS), divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS), polydimethylsiloxane/divinylbenzene (PDMS/DVB), and polydimethylsiloxane (PDMS). As summarized in Table 1, the analysis with these fibers allowed the identification of 13, 13, 14, and 14 compounds, respectively; their relative percentages and retention indexes are also indicated in Table 1. \(\beta\)-Pinene, D-limonene, and myrcene were the major components detected with DVB/CAR/PDMS and CAR/PDMS stationary phases; this composition is consistent with the main compounds detected in EO. On the other hand, cedrene and \(\beta\)-caryophyllene were the most abundant compounds detected with PDMS and PDMS/DVB-coat fibers. Figure 2: Compounds isolated from _B. heterophylla_’s aqueous extract. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**N\({}^{*}\)**} & \multirow{2}{*}{**Compound**} & \multirow{2}{*}{\(\mathbf{I_{R}}\)} & \multicolumn{6}{c}{**Percent of Each Component**} \\ \cline{5-8}  & & & **EO \({}^{*}\)** & **PDMS \({}^{*}\)** & **PDMS/DVS \({}^{*}\)** & **DWB/CAR/PDMS \({}^{*}\)** & **CAR/PDMS \({}^{*}\)** \\ \hline
9 & a-Pinne & 922 & 5.34 & - & - & - & - \\
10 & \(\beta\)-Pinne & 969 & 28.86 & 4.29 & 4.85 & 10.6 & 1.97 \\
11 & Myrene & 982 & 29.57 & 3.43 & 9.4 & 27.19 & 10.53 \\
12 & \(\alpha\)-Cyrene & 1016 & - & - & - & 28.71 \\
13 & D-Limonne & 1019 & 36.24 & 4.07 & 8.82 & 23.02 & 26.71 \\
14 & \(\beta\)-Cyrene & 1081 & - & - & - & - & 3.18 \\
15 & \(\beta\)-Elemente & 1327 & - & 2.45 & 1.34 & - & - \\
16 & Cedren & 1413 & - & 19.99 & 15.62 & - & - \\
17 & \(\beta\)-Caryophyllene & 1414 & - & 19.99 & 15.62 & 9.25 & 4.23 \\
18 & Isogermermcene D & 1422 & - & 8.51 & 5.12 & 1.89 & - \\
19 & Aromandendrene & 1435 & - & 3.64 & 4.01 & - & 1.92 \\
20 & a-Caryophyllene & 1447 & - & 7.37 & 69.5 & 1.72 & 5.03 \\
21 & Germarchee D & 1454 & - & 1.14 & 1.15 & - & - \\
22 & \(\gamma\)-Elemente & 1470 & - & 5.6 & 4.45 & 8.59 & 2 \\
23 & a-Sellinee & 1479 & - & 1.04 & - & - & - \\
24 & \(\beta\)-Cadinne & 1486 & - & - & - & 4.46 \\
25 & \(\beta\)-Amprombe & 1488 & - & - & - & 4.77 & 4.32 \\
26 & \(\beta\)-Himachine & 1493 & - & 9.72 & 8.46 & 1.27 & - \\
27 & \(\beta\)-Amprombe & 1510 & - & - & 3.53 & 4.3 & - \\
28 & Calamenene & 1511 & - & - & - & 4.3 & 3.92 \\
29 & \(\alpha\)-Cadinne & 1525 & - & - & - & 2.45 & 1.6 \\
30 & \(\alpha\)-Calscorene & 1531 & - & 0.39 & 0.4 & 0.64 & - \\ \hline \hline \multicolumn{1}{c}{ Total (\%)} & \multicolumn{1}{c}{100} & 91.63 & 89.72 & 99.99 & 97.28 \\ \hline \end{tabular} \(l_{i}\): Index retention on a DB 5 column with reference to a-halense. \({}^{*}\): Fibers used for its-SPME. \({}^{*}\) Obtained by hydrodiftillation.  
\end{table} 
Table 1: Volatile constituents from \(B\). _Interpolyt_file identified by GC-MS obtained by HS-SPME using different fibers and by hydrodiftillation. Altogether, these results revealed that the mixed polarity DVB/CAR/PDMS fiber was the most suitable to establish the volatile composition of the plant's aerial parts, which is characterized by a high number of hydrocarbons. The total ionic chromatograms of the volatile compounds obtained using this technique are shown in the supplementary materials (Figures S3 and S10).