Supercritical carbon dioxide extraction of squalene and tocopherols from amaranth and assessment of extracts antioxidant activity

Squalene and tocopherols are the most important bioactive constituents in lipophilic amaranth fraction. Therefore, developments of processes of isolation of amaranth extracts enriched with these compounds are of interest. In this study the lipophilic fraction of amaranth seeds was extracted by supercritical fluid extraction with carbon dioxide (SCE-CO₂) under different pressure conditions and by adding 2 and 5% of cosolvent ethanol. The yield of extract varied from 1.37 (15 MPa without cosolvent) to 5.12% (55 MPa and 5% of cosolvent). The highest content of unsaponifiables (21.1%) in the extract was at 55 MPa and 5% of cosolvent; at these conditions the yields of tocopherols and squalene from amaranth seeds were 317.3 mg/kg and 0.289 g/100 g, respectively. Tocopherol isomers in amaranth oil were distributed at the approximate ratio of 1(α-T):27(β-T):6.5(γ-T):5(δ-T). The extract was fractionated in the two separators by gradual decrease of the pressure and it was found that the fraction obtained at ambient conditions contained the highest concentration of tocopherols (up to 7.6 mg/g) and squalene (up to 17.9 g/100 g oil). The highest antioxidant activity measured by the L-ORAC assay possessed the fractions with the highest concentrations of squalene and tocopherols and obtained at 15 MPa with pure CO₂ (235.1 μmol TE/g) and 2% of cosolvent (257.6 μmol TE/g).