Solid/liquid extraction and isolation by molecular distillation of hydroxytyrosol from Olea europaea L. leaves

Molecular distillation, or short-path distillation (SPD), is particularly appropriate for processing of low-volatility compounds, which are easily altered at high temperature. Olea europaea L. leaves constitute an olive tree by-product very interesting for their natural antioxidants content. In this research, molecular distillation technology has been applied to obtain high-value-added compounds by the SPD fractionation of an olive tree leaf extract. The process consists of two stages: (a) ethanolic extraction of the olive leaves, followed by incorporation of the extract into glycerine and (b) molecular distillation of the glycerine enriched in olive leaf extract compounds (terpenic and phenolic compounds). Four molecular distillation tests under different conditions were carried out. Results showed that 80.9% 3,4-dihydroxy-phenylethanol (hydroxytyrosol) was recovered from the glycerine admixture under a pressure of 1.50-2.00 mbar, a temperature of 190 degrees C and a feed rate of 15 mL/min.