Comparison of soxhlet, ultrasound-assisted and pressurized liquid extraction of terpenes, fatty acids and Vitamin E from Piper gaudichaudianum Kunth

This paper describes a comparative study of extraction methods of terpenes (terpenic alcohols and phytosterols), fatty acids and Vitamin E from leaves of Piper gaudichaudianum Kunth. The analysis of extracts was done by gas chromatography with mass spectrometric detection. The identification and quantification was made by co-injections of the extract with certified standards. The use of pressurized liquid extraction (PLE; Dionex trade name: ASE, for accelerated solvent extraction) decrease significantly the total time of extraction, the amount of solvent and the manipulation of sample and solvents in comparison with soxhlet (SE) and ultrasound-assisted (USE). In addition, PLE was more effective for the extractions of terpenes (terpenic alcohols and phytosterols), fatty acids and Vitamin E.     

Chemical composition of mate tea leaves (Ilex paraguariensis): a study of extraction methods

The objective of this work was to investigate the extraction of Ilex paraguariensis leaves by means of three extraction techniques: pressurized liquid extraction (PLE, also called accelerated solvent extraction – ASE), maceration, and sonication. Samples of mate tea leaves were collected from an experiment conducted under agronomic control at Indústria e Comércio de Erva‐Mate Bar?o LTDA, Brazil. Six solvents with increasing polarities (n‐hexane, toluene, dichloromethane, ethyl acetate, acetone, and methanol) were used in this investigation. Chemical analysis of the extracts was performed by GC coupled with a mass spectrometer detector. The identification and quantification were accomplished by coinjections of certified standards. The results showed that no significant differences in the qualities of the extracts were noticed regarding the extraction methods. On the other hand, the PLE technique was found to be more effective for the extractions of caffeine, phytol, palmitic, and stearic acid. The use of PLE led to a significant decrease in the total extraction time, amount of solvent consumption, and manipulation of samples compared to maceration and ultrasound‐assisted extraction methods.     

Hydrogen bonding in phosphonate cavitands: Investigation of host-guest complexes with ammonium salts

The H-bonding in alkylammonium complexes of phosphonate cavitands were studied by mass spectrometric methods and theoretical calculations. The alkylammonium ions included primary, secondary, and tertiary methyl- and ethylammonium ions. Their complexation with mono-, tetra-, and two di-phosphonate cavitands, which differ according to the number and position of H-bond acceptor P = O groups, was evaluated by using different competition experiments, energy-resolved CID, gas-phase H/D-exchange, and ligand-exchange reactions, together with ab initio theoretical optimization of the complexes. The phosphonate cavitands with two or more adjacent P = O groups were found to be selective towards secondary alkylammonium ions, due to simultaneous formation of two stable hydrogen bonds. In the ion-molecule reactions (both H/D- and ligand-exchange), the formation of two stable hydrogen bonds was observed either to slow down the reaction or to completely prevent it. This was, however, limited to situations where two hydrogen bonds are formed between the H-bond donor sites of the alkyl ammonium ion and the vicinal H-bond acceptor sites of the cavitand.     

Protonation of 1, 5-naphthyridine derivatives

The direction of protonation (1-N or 5-N) or 2-, 2,3-, and 2,6-substituted derivatives of 1,5-naphthyridine was determined on the basis of the basicity constants.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 965–968, July, 1977.     

1,5-naphthyridines and their N-oxides

The N-oxidation reactions of 2-hydroxy- and 2-amino-1,5-naphthyridines were investigated. 2-Hydroxy-1,5-naphthyridine 5-oxide and 2-hydroxy-, 2-amino-, and 2-acetamido-1,5-naphthyridine 1,5-dioxides were obtained. The structures of the compounds obtained were proved by means of IR and PMR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1237–1240, September, 1972.     

UV spectra and basicity constants of 2-substituted quinoxalines

The UV spectra of the bases and cations of a number of 2-substituted quinoxaline derivatives were investigated, and their basicity constants were determined. The investigated compounds were divided into two series, characterized, respectively, by ortho and meta orientations of the substituent and cationoid center, on the basis of correlations of the pKa values with the Hammett—Taft constants. The effect of the position of the protonation center relative to the substituent on the energy of the ^* transitions was examined within the framework of the simple MO LCAO method. The results of the calculations are compared with the experimentally observed shift in the¹L_b band in the UV spectra of some 2-substituted quinoxalines on passing from the bases to the monocations.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 398–403, March, 1973.     

E-2-Benzylidenebenzocycloalkanones. IV. Studies on transmission of substituent effects on C NMR chemical shifts of E-2-(X-benzylidene)-1-tetralones, and -benzosuberones. Comparison with the C NMR data of chalcones and E-2-(X-benzylidene)-1-indanones

Single substituent parameter (SSP) and dual substituent parameter (DSP) analyses were applied to study the transmission of substituent effects on selected ¹³C NMR chemical shifts of the cyclic chalcone analogues, E-2-(4′-X-benzylidene)-1-tetralones (2) and E-2-(4′-X-benzylidene)-1-benzosuberones (3). In order to study how the geometry of the cyclic chalcone analogues affects the transmission of substituent effects similar investigations with the respective chalcones (4) were also performed. The results obtained earlier with the five-membered analogue E-2-(4′-X-benzylidene)-1-indanones (1) were also involved in the comparisons. Geometry optimization of the unsubstituted 1a, 2a, 3a and 4a as well as the substituted 2 and 3 was performed by ab initio quantum chemical calculations. Both SSP and DSP analyses reflected that resonance effects contribute more to the chemical shift of C- (C2), while inductive effects primarily affect that of C-β (C10) of the enone moiety of all the four series. This latter effect, however, is far not as pronounced as that of the former one. It was found that DSP analysis data (ρ_F and ρ_R values) of transmission of substituent effects on the δC2 data can serve as a measure of choice to study the conformation (planarity) of the investigated enones in the four series.     

Oxidomolybdenum(VI) complexes with atrane-type [O3N] ligands

Dioxomolybdenum(VI) complex [MoO₂Cl₂(dmso)₂] reacts with a series of tetradentate O₃N-type aminoalcohol–bisphenol ligands to form oxomolybdenum(VI) complexes of type [MoOCl(Lⁿ)]. The reaction of H₃L¹ produces [MoOCl(L¹)] as two separable isomers, whereas the reaction of H₃L² or H₃L³ yields a single product. The X-ray analyses of cis- and trans-[MoOCl(L¹)] reveal that the complexes are formed of monomeric molecules. The ligands have tetradentate coordination through three oxygen donors and one nitrogen donor, which is located trans to the terminal oxo group. The sixth coordination site is occupied by a chloro ligand.