Corina Costescu

Thermal and oxidative stability of the Ocimum basilicum L. essential oil/β-cyclodextrin supramolecular system.

Summary Ocimum basilicum L. essential oil and its β-cyclodextrin (β-CD) complex have been investigated with respect to their stability against the degradative action of air/oxygen and temperature. This supramolecular system was obtained by a crystallization method in order to achieve the equilibrium of complexed–uncomplexed volatile compounds in an ethanol/water solution at 50 °C. Both the raw essential oil and its β-CD complex have been subjected to thermal and oxidative degradation conditions in order to evaluate the protective capacity of β-CD. The relative concentration of the O. basilicum L. essential oil compounds, as determined by GC–MS, varies accordingly with their sensitivity to the thermal and/or oxidative degradation conditions imposed. Furthermore, the relative concentration of the volatile O. basilicum L. compounds found in the β-CD complex is quite different in comparison with the raw material. An increase of the relative concentration of linalool oxide from 0.3% to 1.1%, in addition to many sesquiterpene oxides, has been observed. β-CD complexation of the O. basilicum essential oil modifies the relative concentration of the encapsulated volatile compounds. Thus, linalool was better encapsulated in β-CD, while methylchavicol (estragole) was encapsulated in β-CD at a concentration close to that of the raw essential oil. Higher relative concentrations from the degradation of the oxygenated compounds such as linalool oxide and aromadendren oxide were determined in the raw O. basilicum L. essential oil in comparison with the corresponding β-CD complex. For the first time, the protective capability of natural β-CD for labile basil essential oil compounds has been demonstrated.

Comparative study of Juniperus communis and Juniperus virginiana essential oils: TLC and GC analysis

We report a comparative study of Juniperus virginiana and Juniperus communis essential oils (obtained by hydrodistillation of plant parts from the west of Romania or obtained commercially in Europe) by thin layer chromatographic and gas chromatographic-mass spectrometric analysis. Concentrations of cineole and guaiazulene, key compounds with insect repellent and anti-inflammatory activity, were evaluated. Monoterpenes were more abundant in essential oils from berries (40.2% in J. virginiana essential oil and 34.4% in J. communis essential oil), followed by sesquiterpene alcohols, but the latter were more abundant in essential oils from leaves (26.9% in J. virginiana and 16.9% in J. communis). We also discovered substantial amounts of monoterpene alcohols (8.9–9.5% and 6.4–11.6% for J. virginiana and J. communis, respectively) and sesquiterpenes (more abundant in J. communis essential oils: 21.1% in berries and 12.4% in leaves; in J. virginiana essential oils amounts of sesquiterpenes were only 5.9–6.8%). The key compounds cineole and guaiazulene were present at low absolute concentrations. The first was more abundant in J. communis essential oils (2.6–3.5 µg mL−1); guaiazulene was identified in J. virginiana essential oil only (0.7 µg mL−1 in essential oil from the leaves). Thinlayer chromatographic analysis of Juniperus essential oils revealed the importance of the monoterpenes, sesquiterpenes, and their corresponding alcohols in these mixtures. Cineole and guaiazulene spots from essential oils from autochthonous J. virginiana berries and leaves were very small, and were obscured by more abundant mono and sesquiterpenes (for example limonene) in the upper half of the chromatogram or mono and sesquiterpene alcohols (for example terpinen-4-ol) in the lower half of chromatograms. Similar results were also obtained for J. communis essential oils.