## 4 Discussion  
Hydrodistillation at atmospheric pressure is the most frequently used method of essential oils isolation. The advantage with respect to other isolation methods, e.g., extraction by organic solvents and supercritical CO\({}_{2}\), is that isolates by hydrodistillation do not include non-volatile compounds. The main disadvantage is the formation of artefacts, thermal degradation reactions and hydrolysis, especially for aromatic plants that contain unstable volatile compounds as the main constituents of their essential oils. During hydrodistillation, water as polar solvent accelerates many reactions, especially reactions via carbocations as intermediates. The pH can fall as low as 2.8 during such extraction of the oil [42]. Many of the trace components of essential oils that are detected could well arise during the isolation procedures. Such oils are steam distilled under conditions where organic acids can be liberated from the plant material, and cyclizations of aldehydes and other monoterpene may occur [43]. The action of phosphatases must be inhibited. The latter cleave phosphate esters to give the free alcohols characteristic of isolated plant oils. The distribution of terpene alcohols between free and esterified forms in vivo is not known in any particular oil, but considerable amounts of the latter and other bonded forms (e.g., glucosides and esters) are probably present [44]. Oils that have been obtained from plant material which has been gathered and stored may also contain products of photolysis, oxidation, and other chemical modification. Such contaminants are often extremely important as regards odor and flavor for commercial use [45]. The distilled oil of _Citrus deliciosa Tenore_ var. _Cai_ was characterized by aromatic nuances making the oil less appreciated (inferior quality) than the cold-pressed oil. Probably as consequence of artifacts formation during the distillation process [46]. The artifact compounds that formed during distillation of _O. basilicum_ leave were: camphene, octan-3-one, delta-2-carene, gamma-terpinene, n-octanol, terpinolene, borneol, terpinen-4-ol, bornyl acetate, alpha-terpinyl acetate, beta-cubebene, beta-longipinene, (Z)-caryophyllene, cadina-3,5-diene, cis-beta-guaiene, gamma-amorphene, gamma-patchoulene,trans-cycloisolongifol-5-ol, delta-cadinene, beta-sesquiphellandrene, 10-epi-cubebol, cis-muurol-5-en-4-beta-ol, cis-muurol-5-en-4-alpha-ol, spathulenol, \(\alpha\)-cadinol, 7-epi-\(\alpha\)-eudesmol. These compounds are present in very low concentrations from 0.01 to 0.76 except for bornyl acetate which was formed in significant quantities (2.77 \(\pm\) 0.22%). Some of these compounds have already been reported in the literature as artifacts produced during distillation or during the storage of essential oil. [PERSON] [47] reported that several mono- and sesquiterpene derivatives (e.g., linalool oxides, p-cymene, (Z)-caryophyllene) might originate as artefacts during distillation. Germacrenes readily converts to calenines, muurolenes, and elemene-type sesquiterpene hydrocarbons [48]. During the distillation of _Abies x amoldiana_[PERSON], and _A. veitchii_[PERSON]. various artifacts, including a derivative of borneol, were formed [49]. Moreover, during the distillation time, acid-catalyzed hydrolysis of bornyl acetate takes place. This hydrolysis only takes place to a small extent during distillation. On the basis of hydrodiffusion, the oxygenated compounds are available for distillation much faster than the hydrocarbons. Thus, bornyl acetate is in contact with the acidic medium for a relatively short period, whereby extreme hydrolysis of this compound is prevented [49]. Distilled EO generally increase their proportion in oxygenated monoterpenes (alphaterpineol, 4-terpineol and sabinene hydrates) that could originate as a result of the process (artifacts).