Isolation and structural characterization of the milled wood lignin, dioxane lignin, and cellulolytic lignin preparations from brewer's spent grain.

The structure of the lignin from brewer's spent grain (BSG) has been studied in detail. Three different lignin preparations, the so-called "milled-wood" lignin (MWL), dioxane lignin (DL), and cellulolytic lignin (CEL), were isolated from BSG and then thoroughly characterized by pyrolysis GC/MS, 2D-NMR, and derivatization followed by reductive cleavage (DFRC). The data indicated that BSG lignin presents a predominance of guaiacyl units (syringyl/guaiacyl ratio of 0.4-0.5) with significant amounts of associated p-coumarates and ferulates. The flavone tricin was also present in the lignin from BSG, as also occurred in other grasses. 2D-NMR (HSQC) revealed that the main substructures present are ß-O-4' alkyl-aryl ethers (77-79%) followed by ß-5' phenylcoumarans (11-13%) and lower amounts of ß-ß' resinols (5-6%) and 5-5' dibenzodioxocins (3-5%). The results from 2D-NMR (HMBC) and DFRC indicated that p-coumarates are acylating the γ-carbon of lignin side chains and are mostly involved in condensed structures. DFRC analyses also indicated a minor degree of γ-acylation with acetate groups, which takes place preferentially on S lignin (6% of S units are acetylated) over G lignin (only 1% of G units are acetylated).

A comprehensive characterization of lipids in wheat straw.

The chemical composition of the lipids in wheat straw was studied in detail by gas chromatography and mass spectrometry. Important discrepancies with the data reported in previous papers were found. The predominant lipids identified were series of long-chain free fatty acids (25% of total extract), followed by series of free fatty alcohols (ca. 20%). High molecular weight esters of long chain fatty acids esterified to long chain fatty alcohols were also found (11%), together with lower amounts of other aliphatic series, such as n-alkanes, n-aldehydes, and glycerides (mono-, di-, and triglycerides). Relatively high amounts of ß-diketones (10%), particularly 14,16-hentriacontanedione, which is the second most abundant single compound among the lipids in wheat straw, were also identified. Finally, steroid compounds (steroid hydrocarbons, steroid ketones, free sterols, sterol esters, and sterol glycosides) were also found, with sterols accounting for nearly 14% of all identified compounds.

Lipophilic extractives from the cortex and pith of elephant grass ( Pennisetum purpureum Schumach.) stems.

The composition of lipophilic extractives in the cortex and pith of elephant grass ( Pennisetum purpureum Schumach.) stems was thoroughly studied by gas chromatography-mass spectrometry. The predominant compounds were fatty acids followed by sterols (in free and conjugated forms as esters and glycosides). Other steroid compounds, as steroid hydrocarbons and ketones, were also present. Additionally, important amounts of mono-, di-, and triglycerides were identified. Other aliphatic series such as n-alkanes, n-fatty alcohols, and n-alkyl ferulates, together with tocopherols and a series of high molecular weight esters, were also found, although in minor amounts. The analyses also revealed the presence of a ß-diketone (12,14-tritriacontanedione), which was particularly abundant in the cortex. Finally, two lignans, matairesinol and syringaresinol, were also detected. In general terms, the abundances of the different classes of compounds were higher in the pith, except for the series of n-fatty alcohols, n-alkyl ferulates, ß-diketones, and lignans, which were more prominent in the cortex.