Yield and Composition of the Essential Oil of Clinopodium nepeta subsp. spruneri as Affected by Harvest Season and Cultivation Method, i.e., Outdoor, Greenhouse and In Vitro Culture.

Clinopodium nepeta subsp. spruneri is an aromatic herb with a mint-oregano flavor, used in Mediterranean regions in traditional medicine. The aerial parts of the plant are rich in essential oil that has antioxidant, antimicrobial and anti-inflammatory properties as well as insecticidal activity. The aim of our work was to determine the yield and composition of the essential oil of the plant, in relation to the harvest season and cultivation method, i.e., outdoor, greenhouse and in vitro culture, using gas chromatography-mass spectrometry (GC-MS) as an analytical tool. Essential oil yield fluctuated similarly in outdoor and greenhouse plants during the year (0.9-2.6%), with higher percentages (2.1-2.6%) in the hottest periods June-October (flowering stage) and April (vegetative stage), and was similar to the yield in in vitro plants (1.7%). More compounds were identified in the oil of outdoor and greenhouse plants (35) compared to that of in vitro plants (21), while the main compounds were the same, i.e., pulegone (13.0-32.0%, highest in February-April, 15.0% in vitro), piperitenone oxide (3.8-31.8%, lowest in February, 34.2% in vitro), piperitone epoxide (4.6-16.4%, highest in February, 15.5% in vitro), D-limonene (2.1-8.8%, lowest in February, 10.0% in vitro), isomenthone (2.3-23.0%, highest in February, 4.6% in vitro), germacrene D (1.9-6.5% highest in December-April, 2.9% in vitro) and dicyclogermacrene (2.1-5.3%, highest in December-April, 5.2% in vitro). Therefore, greenhouse and in vitro cultures were equally efficient in yielding essential oil and its constituents as outdoor cultivation, while in outdoor and greenhouse cultivations, the harvest season, mainly due to the prevailing ambient temperatures, affected the essential oil yield and its percentage composition.

Comparison of distillation and ultrasound-assisted extraction methods for the isolation of sensitive aroma compounds from garlic (Allium sativum).

A comparative study of traditional simultaneous distillation extraction (SDE), microwave assisted hydrodistillation extraction (MWHD) and ultrasound-assisted extraction (USE) is presented, for the extraction of essential oils from fresh garlic (Allium sativum) cloves. Each method is evaluated in terms of qualitative and quantitative composition of the isolated essential oil. The highly reactive sulfur molecules of the garlic volatile fraction show variable response to the different isolation methods. The application of ultrasound for the extraction of the essential oil is considered to cause a lesser damage of thermal-sensitive molecules, thus, providing a better approach of the compounds primarily responsible for the characteristic odor and taste of freshly chopped garlic. All heat-involving isolation procedures have been shown to differentiate the volatile-fraction profile as analyzed by GC-MS. Especially when grouping the compounds into cyclic and acyclic, the percentage concentrations drop from 77.4% to 8.7% for the acyclic while that of the cyclic compounds increase from 4.7% to 70.8%. The observed fact may be attributed to the effect of the heat applied, which changes from harsh thermal treatment (SDE) to short time thermal (MWHD) and room-temperature isolation (USE). The use of USE proves to be crucial in order to provide reliable insight into garlic's chemistry.

Rapid method for simultaneous quantitative determination of four major essential oil components from oregano (Oreganumsp.) and thyme (Thymus sp.) using FT-Raman spectroscopy.

A simple and rapid method for the quantitative determination of four major components found in oregano and thyme essential oils is presented. The method correlates the Raman peak intensity in the spectral region from 1800 to 600 cm(-1) and the concentration percentage of each particular constituent in the sample. To achieve accurate quantification results and avoid the risk of overlapping peaks of unknown Raman-active substances in natural essential oils, the peaks must be analyzed. For this purpose, PEAKSOLVE software (Ver. 1.0.5) was used. Unknown samples were measured with the FT-Raman method, and the results were compared to those of the gas chromatographic (GC) analysis. The comparison was made at a confidence level of 99%, and the two methods scored equally in terms of repeatability and accuracy even at the edge of the method specifications. The new method can provide accurate results in very short times once the setup is complete and could be utilized in areas where vast amounts of samples must be analyzed.

Qualitative determination of volatile compounds and quantitative evaluation of safranal and 4-hydroxy-2,6,6-trimethyl-1-cyclohexene-1-carboxaldehyde (HTCC) in Greek saffron.

Safranal (2,6,6-trimethyl-1,3-cyclohexadiene-1-carboxaldehyde) is the main component of saffron's essential oil. It was obtained using microsimultaneous hydro distillation-extraction (MSDE) and by ultrasound-assisted extraction (USE), which is a mild method. 4-Hydroxy-2,6,6-trimethyl-1-cyclohexene-1-carboxaldehyde (HTCC) is a precursor of safranal and was obtained in considerable amounts only by USE. Five C(13)-norisoprenoids were found in saffron for the first time. Using a gas chromatography technique, safranal and HTCC were quantified from Greek saffron samples. The quantity of safranal isolated by MSDE ranged between 288.1 and 687.9 mg/100 g of saffron, whereas in the case of USE safranal and HTCC ranged between 40.7 and 647.7 mg/100 g of saffron and between 41.7 and 397.7 mg/100 g of saffron, respectively. Freeze-drying was also tested as an alternative drying method. Over years of storage at 4 degrees C the quantity of safranal remained mostly constant while the quantity of HTCC decreased over the same periods.

Characterization of essential oils from lamiaceae species by fourier transform Raman spectroscopy.

The Fourier transform Raman (FT-Raman) spectra of pure terpenes and essential oils obtained by hydrodistillation of some Lamiaceae species, are presented. This study shows that principal components of an essential oil can be recognized by FT-Raman. Components predicted by FT-Raman spectrum of an essential oil correlate well with those found as major constituents by GC-MS. In this way the basic chemical character of an essential oil can be recognized. The results demonstrate that certain Raman intensities can be correlated to specific terpenes and therefore FT-Raman can discriminate between the essential oils of which main components belong to different classes of compounds.