## 2 Results and Discussion
### GC-MS Volatile Compounds Analysis
\begin{table}
\begin{tabular}{l c c c c c c c c c} \hline
**RT** & **Compound** & **LRI** & **BP1** & **BP2** & **BP3** & **BP4** & **BP5** & **BP6** & **BP7** \\ \hline
**26.0** & Ethyl decanoate & 1377 & nd & \(2.5\pm 0.4\) & \(4.8\pm 0.2\) & nd & nd & nd & nd \\
**26.4** & 1,3,5-methoxy-benzene & 1386 & nd & \(5.5\pm 1.3\) & nd & nd & nd & nd \\
**26.5** & Dodecan & 1388 & \(1.1\pm 0.3\) & nd & nd & nd & nd & nd \\
**28.0** & Neryrolactone & 1423 & nd & nd & \(16.5\pm 0.7\) & nd & \(3.1\pm 0.1\) & nd & nd \\
**28.0** & 6,10-dimethyl-5,9-undecadiem-2-one & 1425 & \(6.4\pm 1.5\) & \(7.4\pm 8.1\) & nd & nd & nd & \(15.9\pm 0.2\) & nd \\
**29.6** & 2,6,10-trimethyltetradacane & 1462 & nd & nd & nd & \(0.6\pm 0.4\) & nd & nd \\
**30.1** & Headacene & 1474 & nd & nd & nd & \(6.9\pm 1.8\) & \(5.9\pm 0.7\) & nd & nd \\
**31.2** & Methyl dodecanoate & 1500 & \(4.4\pm 0.5\) & \(102.2\pm 5.5\) & nd & nd & nd & nd \\
**33.2** & 7,-headacene & 1551 & nd & nd & \(4.4\pm 0.7\) & nd & nd & nd & nd \\
**36.3** & 9,12,15-octadecantirel & 1642 & nd & \(14.4\pm 0.2\) & nd & \(0.4\pm 0.9\) & \(2.1\pm 0.1\) & nd & nd \\
**36.4** & 9,12,15-octadecantirel & 1634 & \(2.7\pm 0.9\) & nd & nd & nd & nd & nd \\
**36.5** & Octadyene & 1636 & nd & nd & \(4.3\pm 0.3\) & nd & nd & nd & nd \\
**37.0** & 8-beptadecene & 1649 & \(36.5\pm 1.2\) & nd & \(21.7\pm 2.2\) & \(21.7\pm 1.0\) & \(10.9\pm 5.1\) & nd \\
**37.8** & Nonadecane & 1671 & \(6.4\pm 3.0\) & nd & \(22.1\pm 1.3\) & \(10.4\pm 0.7\) & \(9.1\pm 0.8\) & \(14.4\pm 2.1\) & nd \\ \hline \end{tabular} RT: Retention time (time); LRI: Linear Retention Index determined using a DB-5 MS fused silica column, relative to a series of n-alkens (C7-C6); nd: non detected The values are expressed as relative percentages (v).  
\end{table} 
Table 4. Cont. Although there are compounds, such as nonanal, hexanal, or methyl-5-hepten-2-one, which are abundantly common, in all samples, there are other compounds that are more specific. _Cardulus_ sp., sample BP1, showed some specific carbonyl derivatives, such as benzaldehyde, dodecanal, 3,5,5-trimethyl-3-cyclohex-1-one, or fatty acids such as decanoic acid. Moreover, _Ligustrum_/_Olea_ sp. pollen, sample BP2, revealed the presence of jasmone and 1,3,5-trimethoxy-benzene, whereas the terpen, eucalypt and linalool, appear distinctly in sample BP6, which is dominated by _Rubus_ sp. It is relevant to note that although samples BP4 and BP6 are from the same genus, their volatile profile does not overlap, which may reflect the differences found between the species; this is understandable considering that the pollen was collected from distinct geographical origins. In sample BP3, from _Cistaceae_ sp., the presence of unsaturated hydrocarbons, such as 7-hexadecene and octadecyne, seems to differ between pollen samples, but replacetone, which is only found in BP5, also stands out due to the high quantity found. For _Castane_ sp., the most specific compound is the alcohol, octanol, but it is important to note that the presence of nonanal is at least six times higher than in any other samples. Previous studies concerning volatile and semi-volatile organic compounds, secreted by bee glands, reported (_E_)-cital as an orientation pheromone secreted by the worker bees' Nasonov gland [38]. The same compound was detected in both BP4 and BP5 samples. Moreover, nonanal was detected in worker bees' pheromone samples, as were octanol, hexanol, benzaldehyde, and cryophyllene, which were also reported in other studies [39; 40].