## 3 Results and Discussion  
### Optimisation of HS-SPME-GC-MS Conditions  
Optimization was performed to achieve the simultaneous detection of the highest possible number of volatile compounds. First of all, the BP-20 capillary column was chosen instead of the HP-5 capillary column, as more peaks were observed in the polar BP-20 column. This indicates that the analyzed samples contained more polar compounds. The cho sen column has a very polar polyethene glycol (PEG) stationary phase, suited for analysing alcohols, ketones, aldehydes, and esters. At the same time, HP-5 is a precision-engineered (5%-phenyl)-methylpolysiloxane low polarity column. The results are consistent with the expectations, as according some authors the major secondary volatile metabolites from plant origin are better retained and seen in polar capillary columns like the BP-20 one [30; 31]. In optimizing SPME extraction, many compounds were seen using DVB/CAR/PDMS fibre with adsorbent, bipolar coating suitable for 40-350 analyte molecular weight range. Polar analytes are better extracted using polar/bipolar fibres. The obtained results agree with the literature [24; 32; 33] as triphasic fibre is the most effective for sample compounds in a wide range of volatility and polarity. Moreover, coatings with adsorbent properties are better for trace level analytes with a narrower linear range. The optimum extraction conditions were as follows: extraction temperature: 80 \({}^{\circ}\)C, extraction time: 30 min and desorption time: 2 min. \begin{table}
\begin{tabular}{l l} \hline \hline
**Number** & **Compound** \\ \hline
1 & 4-Ethydlecane \\ \hline
2 & Docosyl octyl ether \\ \hline
3 & 3,8-Dimethyldecane \\ \hline
4 & Lysergamide \\ \hline
5 & 1-Iodododecane \\ \hline
6 & Dodecane \\ \hline
7 & 3,8-Dimethylundecane \\ \hline
8 & 4-Ethylundecane \\ \hline
9 & 2,3,7-Trimethyldecane \\ \hline
10 & 5-Ethyl-5-methyldecane \\ \hline
11 & 2,3,6-Trimethyldecane \\ \hline
12 & 5-Ethylundecane \\ \hline
13 & 3,5-Dimethylpiperidine \\ \hline
14 & 4,8-Dimethylundecane \\ \hline
15 & Tridecane \\ \hline
16 & Docosyl nonyl ether \\ \hline
17 & 2-Hexyl-1-decanol \\ \hline
18 & 1-Hexadecanol \\ \hline
19 & 1,2,4-Trimethylcyclohexane \\ \hline
20 & 6-Methyl-5-hepten-2-one \\ \hline
21 & 1-Iodotetradecane \\ \hline
22 & Tetradecane \\ \hline
23 & Eicosyl nonyl ether \\ \hline
24 & Methoxyacetic acid 2-tetradecyl ester \\ \hline
25 & Heptyl isobutyl ketone \\ \hline
26 & 1,3-bis(1,1-Dimethylethyl)-benzene \\ \hline
27 & Pentadecane \\ \hline
28 & 2,4-Heptadienal \\ \hline
29 & 3-Ethyl-1,4-hexadiene \\ \hline
30 & 2-Methylpentadecane \\ \hline
31 & Hexadecane \\ \hline
32 & 2,6,6-Trimethyl-1-cyclohexene-1-carboxaldehyde \\ \hline
33 & Fumaric acid 3-methylbut-3-enyl undecyl ester \\ \hline
34 & 2,4-Dimethylbenzaldehyde \\ \hline
35 & Geranyl acetone isomer 1 \\ \hline
36 & Tricyclq[4,4,0,0(2,8)]decane \\ \hline
37 & 3-Buten-2-one \\ \hline
38 & \(\beta\)-Ionone \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Legend for Figure 1 presenting list of compounds numbered on the chromatogram. Table 1 presented in Appendix A, shows the compounds and their structures determined in _Arctostaphylos uwa-ursi_ leaves samples using untargeted metabolomics. Table 2 presented Appendix A, shows the compounds identified in different samples and their chemical classification. During the screening of _Arctostaphylos uwa-ursi_ leaves samples, 107 different volatile compounds were detected. They were classified according to their chemical groups. Analyzing the data from the AOX point of view, the most interesting detected compounds were aromatic compounds, then phenols and finally esters. Esters are organic chemical compounds condensation products of acids and alcohols or phenols. Strong antioxidants can be distinguished among them, such as fumaric and oxalic acid esters [34; 35] and dihydroxymethyljasmonate, which were proven to reduce the decay and improve the antioxidant capacities of berries [36].