Twenty-four steam-distilled samples of essential oils from inflorescences from Origanum vulgare
ssp. hirtum (Link) Ietswaart growing wild in Calabria, southern Italy, were analyzed by gas
chromatography and gas chromatography/mass spectrometry. A total of 56 compounds were
identified. The main components of the essential oil were thymol and carvacrol, while their biogenetic
precursors, p-cymene and γ-terpinene, were the most aboundant monoterpenes. The relative
amounts of the two main constituents were comparable to the literature data on this species. Four
chemotypes were identified in Calabria on the basis of the phenolic content, i.e., thymol, carvacrol,
thymol/carvacrol, and carvacrol/thymol chemotypes. The first chemotype was the most frequent.
A significant variability of composition possibly correlated with the individual genotypes was
observed.
Keywords: Oregano; Origanum vulgare ssp. hirtum; essential oil composition; GC/MS
The use of pyrolysis/gas chromatography/mass spectrometry (PY/GC/MS) to determine the molecular composition of lignocellulose is reviewed and the technique illustrated with applications on some novel systems. Constituents and structural arrangement of lignocellulosic polymers in plant cell wall are briefly described. The basic principles of pyrolysis and the main advantages and disadvantages of PY/GC/MS are discussed. PY/GC/MS analyses of (a) paper industry effluents, (b) agricultural by-products subjected to biological processes of delignification and (c) recycled paper are presented as examples of the amount of information that PY/GC/MS can provide on lignin classification and monitoring of delignification treatments as well as on the fingerprinting of lignocellulosic materials. The ion trap detector mass spectra of 56 pyrolysis products of lignocellulose, including compounds of phenolic, furanic and pyranic nature, are shown.
Lignin is one of the components, with cellulose and hemicellulose, of cell walls in all terrestrial plants. Lignin is an amorphous, three-dimensional, polyphenolic molecule charged with the function of giving strength and impermeability to the plant structure. The determination of its molecular weight and structure is still problematic owing to the difficulties in isolation of lignin from the other cell wall constituents. The present work reports the experimental conditions for matrix-assisted laser desorptionlionization time-of-iiight mass spectrometry for the characterization of different types of natural lignins and of one synthetic lignin. A nitrogen laser (A=337 nm) was used for ion desorption and sinapinic acid (3,5-dimethoxy-4-hydroxycinnamic acid) was chosen as the best matrix for lignin analysis. Data on the molecular weight distribution of oligomers in lignin and information on the monomeric constituents of different types of lignin are shown.
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