Alternative strategies for the extraction of compounds from natural resources

Abstract

[Excerpt] Exploitable compounds from natural resources include polysaccharides, proteins and peptides, gum exudates, lipids, polyphenols and other secondary metabolites. Traditional-water extraction (TWE) of polysaccharides is a time-consuming process that requires high solvent and energy consumptions and generates large amounts of waste. Other bioactive compounds are traditionally extracted with organic solvents or mixtures of organic solvents and water, with or without heat. Subcritical water extraction and hydrolysis have been used as an alternative to traditional solvent extraction for many compounds in different matrices (1). Advantages include absence of chemical solvents, lower solvent costs, lower extraction times at moderate operational conditions, resulting in higher quality extracts. Furthermore, water is a solvent with very interesting properties in subcritical conditions. As temperature increases hydrogen bonds break, significantly decreasing the dielectric constant and the polarity, thus increasing solubility of more hydrophobic compounds. On the other hand water ionization increases (thus increasing H+ and OH- ions concentration), meaning that reactions catalysed by acids or bases, like biomass hydrolysis, are accelerated. [...]