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DFT calculations on the photoisomerization of hydrazones of 1,2,4-oxadiazole derivatives to 1,2,5-triazoles have been performed showing that the reaction occurred through the first excited singlet state. The Z isomer gave the reaction through a hydrogen atom transfer of the hydrazonic nitrogen atom to the nitrogen atom in four position on the oxadiazole ring. In this case, the isomerization was a concerted reaction. The E isomer could undergo the same reaction. However, it could not be a concerted reaction but required the presence of a ring opening intermediate. [ABSTRACT FROM AUTHOR]

Numerous investigations on the antioxidant properties of different plant tissue extracts are available in literature, but few studies on the effect of thermally modified wood on secondary metabolites were carried out up to now. This study highlights the influence of the thermal modification of Castanea sativa Mill. wood on total content of antioxidant compounds and consequently on its antioxidant activity. In addition, a chemical profile by Gas Chromatography–Mass Spectrometry (GC–MS) of the extractives was carried out. Wood of chestnut, thermally modified at 180 °C for 3 h, was used to obtain wood meal which was subjected to different extraction techniques, as maceration extraction (ME), ultrasound assisted extraction (UAE) and accelerated solvent extraction (ASE). The total content of principal antioxidant compounds, such as polyphenols, flavonoids and tannins, as well as the evaluation of antioxidant capacity by using different in vitro assays were determined. Relative Antioxidant Capacity Index (RACI), which is used to compare all antioxidant parameters, has also been applied. The study demonstrated a positive influence on chemical compounds present in C. sativa Mill wood originating from the thermal modification process. Thus, is possible to consider thermal modification as a promising strategy to improve the antioxidant activity of chestnut wood extractives. [ABSTRACT FROM AUTHOR]

The SPME-GC-MS analysis of the aroma components of Cephalanthera damasonium, Cephalanthera rubra, and Cephalanthera longifolia were reported. The main components found in C. damasonium were pentadecane, hexadecane, heptadecane and α-farnesene. The same compounds were found in the scent of C. rubra. Although C. damasonium and C. rubra have different pollination mechanisms, their spectrum of volatile compounds surprisingly does not differ significantly. In C. longifolia pentadecane and heptadecane were found together with cis-β-farnesene. As C. longifolia is allogamous, the differences in scent composition may play a role in pollinator attraction. [ABSTRACT FROM AUTHOR]

Platanthera bifolia subsp. osca sample collected at Grisolia showed as main components linalool (17.8%), benzyl benzoate (55.8%), and benzyl 2-hydroxybenzoate (6.7%). Four samples of P. bifolia subsp. osca were collected at Pignola: the main components of the aroma are lilac derivatives (49.02–79.00%), mainly lilac alcohols B (7.41–13.52%), C (10.10–18.45%), and D (7.50–34.28%). Three samples were analyzed from the site of Marsico Nuovo. The main components of the scent found in this site were linalool (1.54–10.00%), lilac aldehydes (3.98–11.15%), and mainly lilac alcohols (50.68–61.51%). The main components of the sample collected at Palena were methyl benzoate (9.04%) and benzyl benzoate (74.72%). The analysis of the composition of the aroma of a Platanthera chlorantha plant has been performed. The main components were lilac derivatives. The reported behavior could be explained admitting an adaptive modification of the scent considering the nature of possible pollinating agents due to different habitats. [ABSTRACT FROM AUTHOR]

The composition and the relative variation of secondary metabolites of Paulownia tomentosa S. wood under thermal effect is a little explored area. Wood material was previously thermo-treated at 210 °C for 3 hours using a press vacuum technology. Extractives of untreated and thermo-treated wood material achieved with Soxhlet extraction techniques were obtained. Then the extracts were chromatographed by using thin layer chromatography. Component groups in extracts were determined by gas chromatography in combination with mass spectrometry. In terms of wood change the thermo-treatment of wood induces a darkening of wood color surface (ΔL* = 28.3), an increase of mass loss (3.5%) and an increase of the amount of extractives and lignin content as well as an increase of the chloroform soluble fraction. This work mainly describes the chemical exploration of the extract from paulownia wood, leading to the isolation and identification of episesamin. [ABSTRACT FROM AUTHOR]

The synthesis, characterization and photoreactivity of a series of new heteroaryl imines form the coupling between 2-benzothienyldiphenylmethyliminophosphorane and heterocyclic aldehydes are described. The reaction at 60 degree Celsius gave the formation of only the trans isomer while at high temperature cis isomer was obtained and only the cis isomers showed a photochemical reactivity to give corresponding condensed pyridine derivative.

The photochemical reaction between an excited state of carbonyl compounds and an alkene to give the oxetane deriving from a cycloaddition reaction (the Paternò–Büchi reaction) is presented. The mechanism of the reaction is discussed on the basis of kinetic, spectroscopic, and theoretical evidence, showing that the reaction can involve both singlet and triplet excited states of the carbonyl compounds, the high probable presence of an exciplex, and the possible presence of electron transfer processes, and when triplet excited carbonyl compounds are involved, the presence of a biradical intermediate is observed. The reactivity of electron-poor and electron-rich alkenes is discussed. Regio- and stereochemical behavior of the reaction are presented showing that, in some cases, very high regio- and stereoselectivities are obtained. The possible theories explaining this behavior are presented. In this field, the stereoselectivity observed, when chiral auxiliaries are used, when the reaction is performed in organized media, and when the presence of a hydroxyl directing effect can be supposed, is presented. The effect of light, temperature, solvent on the reaction is discussed. The possible application of this reaction in organic synthesis is discussed, presenting both previous synthetic schemes where the synthesis of an oxetane is a key step, the possible use of the oxetane in synthesis, and comparing the photochemical approach with the other approaches used to synthesize the oxetane ring. [ABSTRACT FROM AUTHOR]

The autoclave extraction of Hungarian oak (Quercus frainetto Ten.) wood gave 5.3% extractives. The chloroform soluble fraction obtained from the extracts of Q. frainetto allows to identify sesamin. The insoluble fraction contains mainly ribose and mannose. Water extraction in autoclave of thermo-treated Q. frainetto wood gave a lower amount of extractives (3.31%). The main product of the insoluble fraction was, on the basis of its mass spectrum, the monoacetyl derivative of gallic acid. [ABSTRACT FROM AUTHOR]

The photochemical reaction of 3-carboxymethylcyclohexenone with a cyclohexene bearing a chiral auxiliary group has been examined in a DFT study. GIAO simulation of the NMR spectra (DFT/B3LYP/6-311G++(d,2p) level of theory) is not in agreement with the syn–anti–syn product described in the literature for this reaction but is in agreement with the formation of a syn–cis–syn dimer. The analysis of the frontier orbitals involved in this reaction shows that the main interaction is that between the HOMO of the alkene and the LSOMO of the carbonyl compound in its first excited triplet state. The atomic coefficients do not allow a frontier orbital control of the regiochemistry of the reaction. The study of the possible biradical intermediates and the energies of the transition states involved agree with the formation of a syn–cis–syn biradical intermediate. The coupling of the radical carbon atoms in this biradical intermediate allows the obtainment of a more stable dimer. Furthermore, the coupling reaction occurs via a conrotatory process that is able to give only one of the possible syn–cis–syn dimers. [ABSTRACT FROM AUTHOR]

The purpose of this study is the determination of chemical composition and antioxidant activity of essential oils (EOs) from Saussurea costus (Falc.) Lipsch. Roots have been collected on December of the first plant year (IY) and in April, August and December of the third plant year (I, 6B, D7). A GC analysis was carried out for achieving this purpose. Subsequently, total polyphenol content (TPC) and antioxidant activity measured by DPPH, FRAP and BCB assays were evaluated. Three different statistical methods: Relative Antioxidant Capacity Index (RACI), Pearson's correlation coefficient (r) and PCA, were used to compare results obtained and underline EO relationships. From the results obtained, it was possible to observe how the collection period of the EO, in particular both the month and the year of collection, influences the metabolite profile. [ABSTRACT FROM AUTHOR]