## 2 Results and Discussion
### Volatiles Isolated by Ultrasonic Solvent Extraction  
Ultrasonic solvent extraction (USE) is a well established procedure for the isolation of honey volatiles at room temperature with the advantage over classical shake-flask extraction of significantly reducing the extraction time. In comparison with other isolation methods this method is particularly \begin{table}
\begin{tabular}{l l l l l l l l} \hline
43. & _trans_-\(\beta\)-Damascenone & 1388 & 3.1 & - & - & - & - \\
44. & Tetradecane & 1400 & - & 0.9 & 1.2 & - & - \\
45. & 2-Phenylacetamide & 1406 & - & - & 2.4 & 1.0 & 2.2 \\
46. & 4-Hydroyphenyl ethanol\({}^{*}\) & 1445 & - & - & 2.7 & 1.6 & 0.2 \\
47. & 2-Phenylethyl acetate\({}^{*}\) & 1492 & - & - & 3.7 & 3.2 & 2.7 \\
48. & Pentadecane & 1500 & - & - & 0.4 & - & - \\
49. & 4-Methyl-2,6-bis(1,1- & 1514 & - & 0.2 & - & 0.8 & - \\  & dimethylethyl)phenol & 1520 & - & - & 1.4 & - & 1.0 \\
50. & N-(2-Phenylethyl)acetamide & 1520 & - & - & 1.4 & - & 1.0 \\
51. & 4-Hydroybenzoic acid (\(p\)-salicylic acid) & 1522 & - & - & 1.1 & 0.8 & - \\
52. & 2-Methyldodecan-1-ol\({}^{*}\) & 1545 & - & 0.6 & - & 0.2 & 0.3 \\
53. & 5-Aminoidanone & 1594 & - & - & - & - & 0.4 \\
54. & Hexadecane & 1600 & - & 0.7 & 0.7 & 0.3 & - \\
55. & 3-Hydroxy-\(\beta\)-damascone & 1617 & - & 0.4 & 0.3 & 0.4 & 0.3 \\
56. & 4-Hydroxy-3,5-dimethoxybenzamidealdehyde & 1662 & 0.2 & 7.2 & 34.5 & 33.1 & 35.9 \\  & (\(E\))-3-(4-hydroxy-\(m\)-methoxyphenyl)- & 1743 & - & - & 0.6 & 0.4 & 0.5 \\  & prop-2-enal & 1744 & - & 1.4 & 1.7 & 2.2 & 2.2 \\
58. & Methyl syringae & 1756 & - & - & 0.4 & 0.3 & - \\
59. & 3-(4-Hydroyphenyl)-prop-2-enoic acid & 1793 & - & - & 1.4 & 0.3 & - \\
60. & (\(p\)-coumaric acid) & 1800 & - & 0.5 & 0.8 & 0.4 & - \\
61. & Octadecane & 1840 & - & - & 0.2 & - & 0.7 \\
62. & 4-Hydroxy-3,5-dimethoxybenzoic acid & 1869 & - & 2.6 & 0.8 & 2.2 & 1.4 \\  & 3-(4-Hydroxy-3-methoxyphenyl)-prop-2- & 1874 & - & - & 1.4 & - & - \\
65. & Hexadecan-1-ol & 1882 & - & 5.0 & 4.1 & 4.3 & 3.0 \\
66. & Hexadecanoic acid & 1963 & - & 2.5 & 3.7 & 5.5 & 6.6 \\
67. & Dibuthyl phthalate & 1972 & 0.7 & 4.8 & 0.6 & 1.6 & 0.9 \\
68. & (Z)-Octadec-9-en-1-ol & 2060 & - & 14.4 & 3.8 & 14.9 & 15.8 \\
69. & Octadecan-1-ol & 2084 & - & 3.3 & 0.5 & 4.1 & 3.6 \\
70. & Heneicosane & 2100 & - & 31.5 & 3.7 & 0.2 & - \\
71. & (Z)-Octadec-9-enoic acid & 2147 & - & - & 2.1 & 2.1 & 2.2 \\
72. & Octadecanoic acid & 2181 & - & - & - & 1.6 & 0.2 \\
73. & Tetracosane & 2400 & - & 0.3 & - & 2.5 & 2.6 \\ \cline{2-7}  & Total identified & 89.7 & 91.0 & 86.7 & 88.9 & 85.3 \\ \hline \end{tabular}
\end{table} 
Table 1: _Cont._appropriate for the isolation of semi-volatile and water-soluble honey compounds [11]. However, optimization of the solvent polarity is necessary, since different chemical compositions can be obtained with more polar and less polar solvents [10,12]. Consequently, four solvents of different polarity were used in order to determine the most appropriate ones for the USE method: 1) pentane, 2) diethyl ether (after pentane extraction), 3) mixture of pentane and diethyl ether (1:2 v/v) and 4) dichloromethane. The obtained pentane extract (Table 1, column B) was composed mainly of non-polar hydrocarbons, as well as higher aliphatic saturated and unsaturated fatty acids and alcohols such as heneicosane (31.5%), (\(Z\))-octadec-9-en-1-ol (14.4%), nonane (9.3%) or hexadecan-1-ol (5.0%). All these compounds are, in general, found in different honeys [13]. Syringaldehyde occurred with lowest percentage (7.2%) in comparison with the other extracts. After non-polar compounds were removed by pentane extraction, diethyl ether was applied for further USE of the same sample batch, allowing isolation of more polar honey constituents. In the diethyl ether extract the major identified compound was syringaldehyde (34.5%), followed by minor percentages of the structurally related compounds methyl syringae (1.7%) and syringe acid (0.2%). Great variability of the pentane and diethyl ether extracts composition is noted from Table 1 (columns B and C).