alpha-carotene and acetonitrile

A carotenoid purification method with dual-mode countercurrent chromatography (CCC) for β-carotene, α-carotene and lutein from a fresh carrot extract was developed. The fluorinated liquid benzotrifluoride (IUPAC name: (trifluoromethyl)benzene) was used as a novel modifier in the non-aqueous ternary solvent system n-hexane/benzotrifluoride/acetonitrile. The ternary phase diagram of the type I solvent system was used to select two-phase solvent mixtures which enabled an efficient preparative separation of α-carotene, β-carotene and lutein from concomitant pigments in crude carrot extract. By means of the modifier, high separation factors (α ≥ 1.2) were obtained, allowing baseline resolution between α-carotene and β-carotene due to specific chemical interactions such as π-π molecular interactions. After optimizing the injection step with a pseudo-ternary phase diagram, 51 mg of β-carotene, 32 mg of α-carotene and 4 mg of lutein could be isolated from 100.2mg crude carrot extract in a short time and with high purities of 95% and 99% by using dual-mode CCC, respectively. Temperatures > 22°C had a negative impact on the separation of α-carotene and β-carotene.

Topics: Acetonitriles; beta Carotene; Carotenoids; Countercurrent Distribution; Daucus carota; Fluorobenzenes; Hexanes; Lutein; Solvents; Temperature

β-Carotene (β-Car) was chemically oxidized in a -2e(-) process using 2 mol equiv of NOSbF(6) in a 4:1 ratio (v/v) of dichloromethane:acetonitrile to form the β-carotene dication (β-Car(2+)). Voltammetric monitoring of the chemical oxidation experiments over a range of temperatures indicated that the half-life of β-Car(2+) was approximately 20 min at -60 °C, and approximately 1 min at -30 °C. α-Tocopherol (α-TOH) was chemically oxidized in a -2e(-)/-H(+) process using 2 mol equiv of NOSbF(6) to form the diamagnetic cation (α-TO(+)) which survives indefinitely at -60 °C in a 4:1 ratio (v/v) of dichloromethane:acetonitrile. Cyclic voltammetry experiments indicated that the oxidative peak potential for α-TOH was approximately +0.4 V more positive than the oxidative peak potential of β-Car. When solutions of α-TO(+)/H(+) (prepared by chemical oxidation of α-TOH with 2 NO(+)) were reacted with solutions containing equal molar amounts of β-Car, voltammetric monitoring indicated that α-TOH was quantitatively regenerated and β-Car(2+) was formed in high yield in a homogeneous two-electron transfer, according to the reaction α-TO(+) + H(+) + β-Car → α-TOH + β-Car(2+).

Topics: Acetonitriles; alpha-Tocopherol; beta Carotene; Carotenoids; Cations; Electrochemical Techniques; Electron Transport; Half-Life; Methylene Chloride; Oxidation-Reduction