## 2 Results and Discussion
### The Chemical Composition of C. unshiu Honey Headspace, Volatiles and Semi-Volatiles  
On returning to the hive, the content of the honey-sac is regurgitated into the honeycomb and ripened into honey. Under the honeycomb oxidative atmosphere sensitive honey organic compounds can undergo oxidation [28]. There are only a few studies in which the organic extractives of the honey-sac have been correlated with those of the corresponding honey. The comparison of the components of the extracts of Linden honey and honey-sac contents showed that nectar and honey-sac contents contain many aldehydes which were found as corresponding acids in the honey, while the aliphatic compounds, isoprenoids and the alkaloids remained unchanged [28]. In another research, the major identified terpene in the honey-sac was 3,7-dimethylylocta-1,5-dien-3,7-diol (terpendiol I) and it was found in _Mentha_ spp. honey solvent extracts, but also can transform to hotrienol, the most abundant compound in the honey headspace [27]. Phenylacetaldehyde was dominant compound (34.4%-47.2%; 38.3%-49.1%) of the _C. unshiu_ honey headspace, followed by benzaldehyde (5.8%-9.8%%; 33.3%-6.6%). Among other benzene derivatives, abundant was phenylacetonitrile (2.7%-9.9%; 3.4%-10.2%). Phenylacetaldehyde was strikingly more abundant in comparison with the nectar headspace (HS-NE) and the headspace of the honey-sac (HS-HoS), shown in Table 1, indicating its formation during the honey ripening in the hive, since heat was not applied to the samples. This can be generated from phenylalanine either by enzyme catalysis or by Strecker degradation [29]. A high percentage of phenylacetaldehyde was found in the honey headspace of _Asphodelus microcarpus_ Salz. et Viv. [30]. Phenylacetonitrile was present within percentage ranges similar to those seen in the HS-NE and HS-HoS (Table 1), while benzaldehyde percentages were elevated. In addition to phenylacetonitrile, two aliphatic nitriles were detected in several honey samples with minor percentages (Table 3): ethylisocyanide and 3-methylbutanenitrile. Benzaldehyde was found to be the major volatile from the honey of cambara and willow, but also in lemon and orange honey [17; 29]. Phenylacetonitrile was found in the headspace of dandelion and thyme honeys [31; 32]. octadecan-1-ol (4.5%-11.4%; 3.8%-5.4%) and hexadecan-1-ol (5.8%-15.3%; 2.4%-5.4%). These compounds (except hexadecanoic acid) were found also in the nectar extracts (E-NE) and the honey-sac extract (E-HoS), but cannot be connected with specific botanical origin since they can be transferred from the comb environment [33]. Similar applies for higher alkanes found only in the honey extracts: tetracosane (1.1%-20.8%; 0.1%-29.7%), tricosane (0.3%-26.4%), docosane (0.2%-15.7%; 0.0%-8.5%) or heneicosane (0.0%-3.7%; 0.0%-3.0%). Among interesting compounds of the extracts, 1\(H\)-indole (0.1%-0.3%; 0.1%-2.6%) and 1,3-dihydro-2\(H\)-indol-2-one (0.2%-1.7%; 0.1%-1.3%) can be pointed out, similar to E-NE and E-HoS. Caffeine was also detected in all of the extracts (0.3%-0.8%; 1.2%-7.1%) with lower abundance in comparison to E-NE and E-HoS. In distinction to E-NE and E-HoS, two interesting compounds were present in the honey extracts: 1-hydroxylinalool (0.5%-6.5%; 0.2%-2.0%) and vomifoliol (0.2%-2.0%; 0.2%-2.4%). 1-Hydroxylinalool, previously identified in E-HoS, is a good indicator of linalool transformations providing linalool derivatives found only in the honey headspace. Norisoprenoid vomifoliol was not found in E-NE and E-HoS and, therefore, could be transferred from the comb environment. Pinocembrin (5,7-dihydroxy-2-phenyl-2,3-dihydro-4\(H\)-chromen-4-one) was found only in CH\({}_{2}\)Cl\({}_{2}\) extracts. It is a flavanone, containing the nucleus of heseretin (2,3-dihydro-5,7-dihydroxy-2-(3-hydroxy-4-methoxyphenylyl)-4\(H\)-1-benzopyran-4-one) that was found in _Citrus_ honeys [13]. Due to the high molecular mass of pinocembrin, GC-MS is not a good method for its quantification (as for other flavanones).