## 4 Results and Discussion
### Phenolic Profile: Qualitative and Quantitative Determinations
#### 4.2.4 Volatile Compounds of _Lavandula stocchas_  
Fifty volatile compounds were tentatively identified using HS-SPME/GC-MS, belonging to alcohols, aldehydes, ketones, norisoprenoids and numerous terpenoids. In Table 2 is given (among other data) the percentage contribution of each volatile compound to the total ones. Figure 3 shows a typical gas chromatogram of _Lavandula stocchas_, pointing with numbers to some indicative volatile compounds. The most abundant volatiles were a-thujone (32.14%), 1,3,3-trimethyl-2-oxabicyclo[2.2.2] octane (9.77%), (+)-myrtenyl acetate (7.75%), camphor (6.07%), 1-octen-3-yl-acetate (3.94%) and fenchyl acetate (3.91%), followed by minor proportions of numerous others. A considerable number of these compounds have been reported in the essential oil of plants with edible modified stems, roots and bulbs in the Solanaceae, Tropacolaceae, Typhaceae and Zingiberaceae families, which are grown all over the world [42].  
The biosynthesis of thujone in plants starts with the formation of geranyl diphosphate (GPP) from dimethylallyl pyrophosphate (DMAPP) and isopentenyl diphosphate (IPP), catalyzed by the enzyme geranyl diphosphate synthase [43]. In addition, [PERSON] and [PERSON] [44], using carbon nuclear magnetic spectroscopy (\({}^{13}\)C-NMR), reported that the isoprene units used to form thujone in plants are derived from an alternative pathway, the methylerythitol phosphate pathway (MEP).  
Different opinions occur regarding the use of thujone as a food or drink supplement. In particular, the maximum thujone levels in the E.U. are related to the Artemisia species used along with the matrix (food or beverage). In that sense, the respected range may be within 0.5-35 mg kg\({}^{-1}\)[45; 46].  
On the other hand, in the U.S., the addition of pure thujone to foods is not permitted [47]. Foods or beverages that contain Artemisia species, white cedar, oak moss, tansy or yarrow must be free of thujone [48], which practically means that these contain less than 10 mg L\({}^{-1}\) of thujone [49]. Sage and sage oil (which may contain up to 50% thujone) are on the Food and Drug Administration's list of generally recognized as safe (GRAS) substances [50]. The average lethal dose value, or LD\({}_{50}\), of alpha-thujone, the more active of the two isomers (alpha- and beta-) found in plant-derived products, has been reported to be ca. 45 mg kg\({}^{-1}\) in mice, with a 0% mortality rate at 30 mg kg\({}^{-1}\) and a 100% mortality rate at 60 mg kg\({}^{-1}\), respectively [51].  
The biochemical pathway of camphor production involves the presence of geranyl pyrophosphate, which, via the cyclisation of linaloyl pyrophosphate, turns to bornyl pyrophosphate, followed by hydrolysis to bomeol and then oxidation to camphor. Camphor has been used in traditional medicine since ancient times in countries where it was native. Its characteristic odour and its decongestant effect on the treatment of sprains, swellings and inflammation have probably led to its use in medicine [52; 53]. Camphor was also used for centuries in Chinese medicine for a variety of health issues. The lethal doses in adults are in the range of 50-500 mg kg\({}^{-1}\) after oral exposure. In particular, 2 g may cause serious toxicity and 4 g is potentially lethal [54]. To the best of our knowledge, this is the first report in the literature reporting the volatile profile of Greek _Lavandula stocchas_.  
Figure 3: _Cont._  
Figure 3: A typical gas chromatogram of _Lavanatha stochas_. Indicative volatile compounds (markers) are numbered according to the retention time shown in Table 2. 1: alpha-Pinene, 2. alpha-Fenchene, 3: Camphene, 4: para-Cymene, 5: cis-Linalool oxide, 6: alpha-Thujone, 7: Camphor, 8: alpha-Terpineol, 9: Myrrenal, 10: cis-Geranyl acetate, 11: (+)-Sativene, 12: beta-Selienne, 13: Virridifford, 14: (+)-Aromadendrene.