## 2 Results and Discussion
### Volatile Fingerprint: Terpene Profile and Secondary Lipid's Oxidation Products
\(\alpha\)-Pinene and \(\beta\)-pinene were identified in the majority of samples, excluding samples Oil_3 and Oil_13. This remains unclear considering that the two pinoenes are quite balanced within the different _Cannabis_ varieties representing around the 10% of the terpenes group and not exceeding 15-20% [(20)]. The occurrence of \(\alpha\)-terpinolene in all samples (except Oil_2 and Oil_13), might be important as this compound was suggested as a genetic marker for distinguishing two important gene pools for breeding low-THC varieties [(35; 36)]. Sample Oil_14 was particularly rich in _trans_-caryophyllene followed by \(\alpha\)-humulene. The dominance of those two sesquiterpenes over the other terpenes detected in this preparation may indicate the geographic provenience of the starting _Cannabis sativa_ material, and as a matter of fact, the producer specified the mountain region where the plant was cultivated. Figure 2: Terpenes classes quantified in CBD based oils preparations (expressed as \(\mu\)g/g IS equivalents) (**a**) Mono/di/tri Terpenes (**b**) sesquiterpenes and oxygenated terpenes. It is also important to notice that sample Oil_15 was almost completely deprived of a terpene fraction aside from the traces of the main three mentioned above. This might indicate an inefficient/inadequate processing of the starting materials or even artificial addition of CBD to the oil matrix, as some essential canabinoids were also missing (Table 1). In addition, extremely low terpene content was established for samples 11 and 13, while the remaining samples had total terpene contents in the range between 174 and 1367 \(\mathrm{\SIUnitSymbolMicro g}/\mathrm{g}\), with pronounced variation in composition from sample to sample. Nevertheless, qualitative and quantitative differences observed in the chemical profiles of terpene fractions are conditioned by many factors such as: hemp variety, cultivation and environmental conditions harvest time and post-harvest conditions, storage and drying of raw plants, extraction procedure applied, matrix used and finally storage of the oil formulation. Besides hydrocarbon terpen, oxygenated terpenoids such as linalool and \(\alpha\)-terpineol, were found in some preparations (Table 2, Figure 2) with a notably high concentration again in sample Oil_6. Those compounds correspond to secondary photooxidation products of the initial terpen. In the presence of light and singlet oxygen, terpen are also known to undergo photooxidation leading to the formation of allylic hydroperoxides [35]. In addition to the terpene compound profiles that accounted for more than 90% of the detected volatile constituents of the oils, it was possible to note the presence of other organic compounds commonly found in natural extracts such as esters, alcohols, aldehydes and ketones (Table 2). Only a few low chain esters could actually be identified, with ethyl acetate dominating in sample Oil_3. Its presence is most likely to be due to the preparation method and could also be considered indicative of potential adulteration. On the another hand, the detection of aldehydes and ketones suggests the initiation of lipid peroxidation of polyunsaturated fatty acids (PUFA) in the oils used as a matrix, as demonstrated in our previous work concerning the observed trends of these compounds during storage of macerated _Cannabis_-derived oils [12]. It is well documented that peroxidation of PUFA leads to the formation of a well-defined series of aldehydes and ketones such as nonenal, hexanal and pentanal, 2-heptenal, especially during storage. The rate of formation of lipid oxidation products depends strictly on several factors, among which the most important are the preparation method temperature, fatty acid composition of the oil in which _Cannabis_ extract was dissolved and the storage conditions (storage temperature) as recently demonstrated in a study [12]. These parameters are crucial to define the ultimate characteristics of the final products as evidenced also by the color of the samples (Figure 3).