## 2 Results and Discussion
### Volatile Fingerprint: Terpene Profile and Secondary Lipid's Oxidation Products
Other volatile decomposition compounds frequently encountered include 2-hexenal, 2-ocenal, 2,4-nonadienal, 4,5-dihydroxydecenal [37], some of which also appeared to be present in some of our samples. For the CBD oils analyzed in this study, tree different oil typologies were used: medium chain triglycerides (MCT oil, one sample), olive oil (six samples) and hemp seed oil (eight samples). It is worth emphasizing that sample Oil_4 was almost completely deprived of lipid oxidation products (Table 2, Figure 4). This preparation was the only one prepared in MCT oil, which means that this kind of matrix is less susceptible to oxidative degradation than the olive or hemp seed oils declared as matrices for other preparations enrolled herein  
As far as olive oil is concerned, is often used by producers as it has a strong nutritional potential, being rich in the polyunsaturated fatty acids. Moreover, FU oil (pharmaceutical grade olive oil) is used for the preparation of CBD galenic formulations [9; 12; 29] as it was performed for Bedrolite oil extract. Regarding the hemp seed oil used as a carrier for dissolving the CBD extract (hence the term \"CBD hepp oil\") some clarifications regarding this kind of preparation are indispensable because misconceptions that may confuse the final users of this preparations still exist. \"CBD oil\" expression is typically limited to extracts in oil of flowering buds and not stalks, fibers, or seeds of each _Cannabis sativa_ L. variety. Hemp seeds do not contain any cannabinoids, but their contact with the resin secreted by the epidermal glands located on flowers, and leaves and/or a bad selection of the bracts of the perigonium can cause the appearance of some cannabinoids in hemp oil [34; 38]. Therefore, any cannabinoidsdetected actually represent hemp seed oil contaminants. Their concentration is influenced by the hemp variety and by the seed cleaning process. Although the cannabinoid concentration in hemp seed oils is usually extremely low, it must be determined before oil commercialization [39]. Nevertheless, the seeds of industrial hemp plants have important uses in human nutrition [40; 41] and this is reason why its oil is used as an adequate, naturally resembling matrix for CBD-enriched products. Hemp seed oils represent good sources of protein, and are rich in omega-3 and omega-6 fatty acids with an ideal n3/n6 PUFA nutrition ratio according to WHO guidelines [42; 43]. It should be considered that hemp oil is rich in unsaturated fatty acids which are the components susceptible to oxidation phenomena during storage. Although hemp seed oil was shown to be more predisposed to peroxidation than olive oil [44], this study did not identify any significant differences between these two matrixes as far as on-going peroxidation was concerned. Nevertheless, the critical point is to assess stability during the storage period, that is not reported or available for any of the CBD preparations analysed here. This represents a fundamental issue since the formation of lipid oxidation products is related with the decreasing concentration of cannabinoids and terpen, as well [12]. Therefore, the investigation of trends of compounds characterizing the formulations is essential to define the management conditions. Moreover, an adequate storage temperature would be useful to define the correct expiry date of the products as they are commercialized in EU as dietary supplements. Figure 4: Lipid oxidation products quantified in CBD based oils preparations (expressed as \(\upmu\)g/g SI equivalents). Figure 3: Different colors observed in CBD-based oil products.