Solubility Enhancement of Hydrophobic Compounds in Aqueous Solutions Using Biobased Solvents as Hydrotropes

Improving the aqueous solubility of poorly soluble hydrophobic compounds is a topic of great interest to the pharmaceutical, chemical, and food industries. The poor solubility of these compounds in water poses a challenge in developing sustainable processes for their extraction, separation, and formulation. Therefore, in this study, the use as hydrotropes of biobased solvents such as γ-valerolactone (GVL), Cyrene, ethyl lactate, and alkanediols (1,2-propanediol, 1,5-pentanediol, and 1,6-hexanediol) to improve the solubility of two model compounds (syringic acid and ferulic acid) in water is investigated. The effects of the concentration and structure of biobased solvents on the solubility of phenolic compounds in aqueous solutions at (303.2 ± 0.5) K were studied. The results showed that the aqueous solubility of the phenolic compounds studied typically increased with the log (KOW) of the hydrotrope (1,2-propanediol < Cyrene < 1,5-pentanediol < GVL < ethyl lactate < 1,6-hexanediol) and the hydrophobicity of the solute; the hydrotropic dissolution of phenolic compounds is shown to depend on both the hydrotrope and the solute. This study shows that some biobased solvents, especially GVL, are excellent hydrotropes. Their renewable nature, low price, and low toxicity make these results particularly relevant to the field of extraction and separation of bioactive compounds.