Extraction and purification of ferulic acid from flax shives, wheat and corn bran by alkaline hydrolysis and pressurised solvents

Extraction of ferulic acid and vanillin from flax shives, wheat bran and corn bran were carried out using two extraction methods, non-pressurised alkaline hydrolysis (0.5 M NaOH) and pressurised solvents (0.5 M NaOH, water, ethanol and ammonia). There were no differences in the content of products extracted with non-pressurised and pressurised 0.5 M NaOH solution yielding mostly ferulic acid, p-coumaric acid and small amounts of vanillin. Pressurised low-polarity water (PLPW), pressurised aqueous ethanol (PAE) and pressurised aqueous ammonia (PAA) were efficient in the one-step production of vanillin from ferulic acid in flax shives (guaiacyl-rich), wheat bran and corn bran (ferulic acid-rich). Vanillin was produced from the bound-ferulic acid via cleavage of the aliphatic double bond under the pressurised conditions. Higher content of ferulic acid in the corn bran yielded higher amounts of vanillin compared to wheat bran and flax shives. A simple and efficient purification procedure for ferulic acid from the alkaline extracts is presented. This procedure exploits the solubility of ferulic acid at different ethanol concentrations.