Wheat straw lignin was extracted using the novel CIMV procedure which selectively separates the cellulose, hemicelluloses and lignin. Solid-state (13)C NMR experiments using cross polarization/magic angle spinning (CP/MAS) were carried out on the extracted wheat straw lignin and some structural indices were revealed. Atmospheric pressure photoionization mass spectrometry (APPI-MS) has proven to be a powerful analytical tool capable of ionizing small to large lignin oligomers, which cannot be ionized efficiently by atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI). The APPI mass spectra of the extracted wheat straw lignin were recorded in the positive and negative ion modes. Positive ion mode APPI-MS indicated the exact presence of 39 specific oligomeric ions. Negative ion APPI-MS indicated the additional presence of at least 18 specific oligomeric ions. The structural characterization of this novel and complete series of 57 specific related oligomers was achieved by calculating the exact molecular masses measured by high-resolution quadrupole time-of-flight mass spectrometry (QqToF-MS). Some oligomeric species photoionized in both the positive and negative ion modes to form the respective protonated and deprotonated molecules. Low-energy collision-induced dissociation tandem mass spectrometric analyses performed with a QqToF-MS/MS hybrid instrument provided unique dissociation patterns of the complete series of novel precursor ions. These MS/MS analyses provided diagnostic product ions, which enabled us to determine the exact molecular structures and arrangement of the selected 57 different related ionic species.

This review is devoted to the application of MS using soft ionization methods with a special emphasis on electrospray ionization, atmospheric pressure photoionization and matrix-assisted laser desorption/ionization MS and tandem MS (MS/MS) for the elucidation of the chemical structure of native and modified lignins. We describe and critically evaluate how these soft ionization methods have contributed to the present-day knowledge of the structure of lignins. Herein, we will introduce new nomenclature concerning the chemical state of lignins, namely, virgin released lignins (VRLs) and processed modified lignins (PML). VRLs are obtained by liberation of lignins through degradation of vegetable matter by either chemical hydrolysis and/or enzymatic hydrolysis. PMLs are produced by subjecting the VRL to a series of further chemical transformations and purifications that are likely to alter their original chemical structures. We are proposing that native lignin polymers, present in the lignocellulosic biomass, are not made of macromolecules linked to cellulose fibres as has been frequently reported. Instead, we propose that the lignins are composed of vast series of linear related oligomers, having different lengths that are covalently linked in a criss-cross pattern to cellulose and hemicellulose fibres forming the network of vegetal matter. Consequently, structural elucidation of VRLs, which presumably have not been purified and processed by any other type of additional chemical treatment and purification, may reflect the structure of the native lignin. In this review, we present an introduction to a MS/MS top-down concept of lignin sequencing and how this technique may be used to address the challenge of characterizing the structure of VRLs. Finally, we offer the case that although lignins have been reported to have very high or high molecular weights, they might not exist on the basis that such polymers have never been identified by the mild ionizing techniques used in modern MS.

No abstract

The kernel oils of five different palm species native to the Amazon basin and French Guyana were studied. Those studied were Acrocomia lasiospatha Wall., Astrocaryum vulgare C. Mart., Bactris gasipaes H.B.K., Elaeis oleifera (Kunth) Cortés, and Maximiliana maripa Drude. Lauric and myristic acids were found in all of the oils. Analysis of the unsaponifiable contents, especially the sterol and triterpene alcohol determinations, revealed the preponderance of sitosterol and the presence of two triterpene alcohols (cycloartenol and 24-methylenecycloartanol). Antioxidant (vitamin E) levels were present in small amounts, with the levels being more similar to olive than to palm oil.More than 40% of oils consumed worldwide today are palm (lauric) oils. The two primary palm species exploited are the Cocos nucifera L. and the Elaeis guineensis N.J. Jacq. Both the mesocarp and kernels provide edible oils as well as oils that have industrial applications (e.g., soapmaking, lubricants, cosmetic creams, and surfactants, among others) (1). In this study, we have paid particular attention to five palm species occurring in French Guyana and the Amazonian basin: Acrocomia lasiospatha Wall, Astrocaryum vulgare C. Mart., Bactris gasipaes Kunth, Elaeis oleifera (Kunth) Cortés, and Maximiliana maripa Drude (2,3).Acrocomia lasiospatha is a 10-15 m high, 30-35 cm diameter, spiny-stemmed palm occurring in the savannah. The fruits are brownish-yellow and the mesocarp is very mucilaginous. The palm develops fruit between July and December. Astrocaryum vulgare is a 10-15 m high palm with hard spines that is very common in open areas, such as fields and pastures and as secondary vegetation. The fruits are yellow-orange and drupaceous, and occur between January and August. Bactris gasipaes is a 10-20 m high, spiny-stemmed palm with greenyellow or yellow-orange fruits that occur between November and July. Elaeis oleifera palm is a (prostrate) trunk palm occurring not far from flooded areas. The red-orange drupaceous fruits occur between July and December. The M. maripa palm, also called inaja in Brazil, grows on dry, sandy sites and is generally found in open areas and secondary forest. It is a large-stemmed palm about 18 m high and 20 cm in diameter with long leaves and ovoid drupaceous fruits that are composed of a fibrous outer shell and a viscous mesocarp pulp. The fruits usually appear between January and June and may occasionally appear from October to December also. The FA composition and the unsaponifiable content of these kernel oils have been reported in several works (4-7). In the present study, these earlier results were confirmed and completed with determinations of the sterol, triterpene alcohol (TA), and total tocopherol values. EXPERIMENTAL PROCEDURESMaterials. Fruits were harvested during the ripening season in French Guyana. They were stored at low temperature (−18°C) to avoid the enzymatic degradation of TG.Kernel oil extraction. After shelling the pulp, the seed was ground in a mixer. A 40-g quantity of each sample was place...

High‐performance size‐exclusion chromatography (HPSEC) was used to evaluate the influence of different variables affecting the transesterification of rapeseed oil (RSO) with anhydrous ethanol and sodium ethoxide as catalyst. The effect of temperature, ethanol/RSO molar ratio, catalyst concentration, and time can be interpreted by observing the variations of the reaction medium composition. HPSEC has made the quantitation of ethyl esters, mono‐, di‐, and triglycerides and glycerol possible. The best results for laboratory‐scale reactions were obtained at 80°C with a 6:1 molar ratio of EtOH/RSO and 1% of NaOEt by weight of RSO.