# Chemical Composition of Volatile and Extractive Components of Canary (Tenerife) Propolis
## 3 Discussion  
Until now, there has been only one report on the chemical composition of Canarian (Gran Canaria) propolis [32]. Although Tenerife and Gran Canaria are located close to each other, the composition of their vegetation cover is markedly different: they have many endemic species that are found only on one of them [33]. Therefore, it seems interesting to compare the chemical composition of propolis originating from these islands. The data obtained on the composition of propolis from Tenerife and Gran Canaria differ in many aspects, and in some cases, this may be explained by differences in the experimental technique. For example, the list of VOCs shown in Table 1 determined by the HS-SPME/GC-MS method includes a much larger number of compounds than those isolated from propolis by hydrodistillation, which loses the most volatile compounds. The list of extracted compounds (Table 2) does not contain sugars and related sugar acids and alcohols, while in the work [32], their share in one propolis sample accounts for approximately 56% of TIC, and in the second, approximately 10% of TIC. This is due to the fact that the weakly polar diethyl ether we used for extraction dissolves practically no polar sugars, unlike 70% aqueous ethanol. Another difference is that the authors of the cited work note that the chemical composition of the extracts from both Gran Canaria propolis samples is very similar, while the extracts from the three Tenerife samples show significant differences. For example, in the extract from sample Pr-2, sesquiterpenes, aliphatic alcohols and carbonyl compounds were \begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multicolumn{1}{c}{**Group of Compounds**} & \multicolumn{1}{c}{\(R\)\({}^{IExp}\)} & \multicolumn{1}{c}{\(R\)\({}^{I}\)\({}^{Lit}\)} & \multicolumn{3}{c}{**Sample**} \\ \cline{3-6}  & & & **Pr-1** & **Pr-2** & **Pr-3** \\ \hline \(n\)-heptacosane & 2700 & 2700 & 3.94 & 0.70 & 8.37 \\ \hline \(13\)-methylheptacosane & 2731 & 2731 & 0.23 & N.d. & 0.40 \\ \hline \(n\)-octacosane & 2800 & 2800 & 0.27 & N.d. & 0.58 \\ \hline \(2\)-methyloctacosane & 2860 & 2858 & N.d. & N.d. & 0.15 \\ \hline \(9\)-nonacosene & 2876 & 2875 & N.d. & N.d. & 1.87 \\ \hline \(7\)-nonacosene & 2885 & 2882 & N.d. & 2.63 & N.d. \\ \hline \(n\)-nonacosane & 2900 & 2900 & 2.67 & 0.70 & 6.72 \\ \hline \(9\)-triacontene & 2983 & 2984 & N.d. & N.d. & 0.33 \\ \hline \(n\)-triacontane & 3000 & 3000 & 0.19 & N.d. & 0.36 \\ \hline \(9\)-hentriacontene & 3073 & 3075 & 0.48 & 3.44 & 2.75 \\ \hline \(7\)-hentriacontene & 3081 & 3082 & 0.89 & 4.21 & 3.39 \\ \hline \(n\)-hentriacontane & 3100 & 3100 & 1.42 & N.d. & 4.09 \\ \hline \(9\)-tritriacontane & 3276 & 3277 & 0.82 & 4.24 & 5.49 \\ \hline \(7\)-tritriacontane & 3282 & 3282 & 0.26 & N.d. & N.d. \\ \hline \(n\)-tritriacontane & 3300 & 3300 & 0.31 & N.d. & 0.56 \\ \hline \multicolumn{1}{c}{**Other, including:**} & & **4.10** & **5.48** & **0.14** \\ \hline glycerol, tri-TMS & 1293 & 1294 & trace & 2.11 & 0.14 \\ \hline \(3\),4,5-trimethoxybenzoic acid, TMS & 1832 & 1833 & 0.18 & N.d. & N.d. \\ \hline quinic acid, penta-TMS & 1900 & 1900 & N.d. & 0.61 & N.d. \\ \hline \(1\)-O-octadecyl glycerol, di-TMS & 2699 & 2695 & N.d. & 2.09 & N.d. \\ \hline \(1\)-O-eicosyl glycerol, di-TMS & 2892 & 2893 & 1.01 & 0.67 & N.d. \\ \hline tetracosyl hexadecanoate & \textgreater{}4000 & - & 2.91 & N.d. & N.d. \\ \hline \(\mathbf{NN}\) & & & **6.84** & **10.50** & **3.49** \\ \hline \hline \end{tabular} \({}^{\text{e}}\)N.d.—Not detected; \({}^{\text{e}}\) trace—below 0.01% TIC; \({}^{\text{e}}\)**?—tentatively.  
\end{table} 
Table 2: _Cont._not detected even at trace levels, while extract Pr-3 did not contain phenolic compounds. These differences may be due to the fact that the Tenerife propolis samples were collected from apiaries located at different altitudinal levels (from 600 to 1400 m above sea level) with different floristic compositions.