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The aim of this work is to demonstrate our results on comparison of composition of essential oil fractions obtained by traditional steam distillation and supercritical fluid extraction. The plant materials for the various extraction methods were selected from the Asteraceae and Lamiaceae families. For the supercritical fluid extraction (SFE) carbon dioxide was used as supercritical solvent. The extracts were collected by stage wise precipitation in two separators. The waxy product and extract rich in essential oil were collected in the lst and in the 2nd separator respectively. The traditional water steam distillation (SD) was carried out in the special apparatus of the Hungarian Pharmacopoea (7 th ed.). GC analysis was carried out on capillary silica fused columns coated with DB-1701 and the specific chiral columns coated with Rt-β DEX m or Rt-β DEX sm. Comparing the composition of steam distilled oils with that of volatile SFE fractions the following general characteristics were established. The SFE fractions were richer in monoterpene-esters and poorer in alcohols than the traditional essential oils (clary sage, lavander). Regarding the distribution of the monoterpene and sesquiterpene compounds, the SFE fractions contained sesquiterpene hydrocarbons in higher percentage than the distilled oils (Salvia triloba). Furthermore, the proportion of sesquiterpenes increased in SFE fractions collected successively with time (Salvia officinalis) similar to the ratio of oxygenated monoterpenes to monoterpene hydrocarbons (Rosmarinus officinalis). In other cases it was verified that part of the mono-and sesquiterpenes were present originally in bound form (glycosides) in plants. Thus they appeared only in essential oil fractions after previous acidic treatment (Thymus, Origanum, Satureja species). During the supercritical extraction the azulenogene sesquiterpene lactones did not transform to azulenes (in chamomile, yarrow), but the non volatile SFE fraction of some Asteraceae plants contained sesquiterpene-γ-lactones of unchanged structure.

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The effectiveness and selectivity of different extraction procedures (hydrodistillation, Soxhlet extraction with organic solvents and supercritical fluid extraction) was compared. The main volatile constituents (geraniol, nerol, geranial, neral, geranyl acetate and neryl acetate) of the traditional essential oil obtained by hydrodistillation and supercritical fluid extracts of Dracocephalum moldavica L. were analysed by the gas chromatographic-mass spectrometric method. The supercritical fluid extraction was carried out using fluid carbon dioxide. Extracts were collected by stepwise precipitation in two separators. Fractioned extraction was also performed by interrupting the extraction process at determined time intervals and collecting four succesive fractions from the second separator. The main volatile constituents of the essential oil were geraniol and geranyl acetate. The supercritical extract collected at the beginning of the extraction process was richer in geranyl acetate and neryl acetate and poorer in geraniol than the conventional essential oil.

Authors dealt more than ten years with the analysis of supercritical extracts. For extraction (SFE) carbon dioxide was used as supercritical solvent. Fractionation of extracts was carried out by releasing the separations pressure at two stages. The extracts were collected as separate samples successively in time. The traditional extractions were carried out with steam distillation or by using n-hexane and ethanol in Soxhlet apparatus. For the analysis of volatile compounds GC, GC-MS; of non volatile compounds TLC-densitometry and spectroscopic methods were used. The following general characteristics were established comparing the composition of steam distillated oils with that of volatile SFE fractions. The SFE fractions were richer in monoterpene-esters and poorer in alcohols than the essential oils prepared by traditional way (clary sage, lavandel). Regarding the distributi,n of the monoterpene and sesquiterpene compounds, the SFE fractions contained sesquiterpene hydrocarbon in higher percentage than the distillated oils (e.g. 13-caryophyllene in Salvia fruticosa, (3-caryophyllene, y­muurolene, y-cadinene in Ochnum basilicum). Further the proportion of sesquiterpenes increased in SFE fractions collected successively in time.Significant difference was remarkable in respect of the optical rotationability of lovage oil and SFE fraction which was probably caused by the different ratio between the two ligustilid enantiomers. It was verified in some cases that a part of mono- and sesquiterpenes were present originally in a bounded form (glycosides) in plants. Therefore they appeared in essential oil fractions only after previous acidic treatment (Thymus, Origanum species). During the supercritical extraction the azulenogene sesquiterpene lactones did not transform to azulenes (in chamomile, yarrow), but the non volatile SFE fractions of some Asteraceae plant contained sesquiterpene--lacton of unchanged structure in high quantity (e.g. cnicin in blessed thistle, parthenolide in feverfew). Authors obtained also SFE fractions which were rich in triterpenoids and phytosterols (marigold, common dandelion).