Study of Aromatic Compounds Derived from Sugarcane Bagasse. Part I: Effect of pH

This work aims at increasing the knowledge about the recovery of aromatic compounds from the lignin fraction of sugarcane bagasse, as well as exploring the possibility to recover these fine chemicals of great concern for many industrial sectors. The major natural products contained in the lignin fraction of such a straw material were extracted in previous work by alkaline hydrolysis using different concentrations of NaOH and amounts of bagasse, and HPLC analyses revealed that the extracts mainly contained p‐coumaric acid, ferulic acid, syringic acid, and vanillin, the first three containing and the last lacking a carboxyl group. All these aromatic compounds have well‐known antioxidant power and are very important in pharmacology. For these reasons, they have been investigated in this study by UV spectrophotometry, with special concern to the pH effect on their spectra and determination of their pK_a values.     

Comparative Study of Ozonation of Two Lignin Model Compounds: Coniferyl Alcohol and Ferulic Acid. Identification of some by-Products

The objective of our study was to compare the reactivity of coniferyl alcohol and ferulic acid with ozone at acidic pH in terms of ozone demand and byproducts formation. Both structures exert an ozone demand of about two moles of ozone per mole of initial compound. Similar ozonation byproducts were identified using gas chromatography/mass spectrometry analysis. Using a low ozone dose (below the ozone demand), byproducts were principally aromatic structures, with vanillin, 3,4-dihydroxy-5-meth-oxybenzaldehyde and vanillic acid as the main compounds. Applying a higher ozone dose (above the ozone demand), furan structures were produced. A reaction mechanism is suggested to explain the formation of such structures. A quantitative study showed that coniferyl alcohol was a stronger precursor of vanillin and vanillic acid than ferulic acid.