Evaluation of the Effect of Different Co-Solvent Mixtures on the Supercritical CO2 Extraction of the Phenolic Compounds Present in Moringa oleifera Lam. Leaves

Supercritical fluid extraction (SFE), using CO2, is a novel, sustainable and very efficient technique for the recovery of highly apolar compounds. However, the recovery of phenolic compounds requires the use of different co-solvent combinations such as water and ethanol to enhance the recovery of these compounds through the optimization of a number of variables. In this sense, the effect of pressure (100, 150 and 200 bar), temperature (50, 65 and 80 degrees C), extraction time (30, 60, 90, 120, 150 and 180 min) and the effect of the different percentages of ethanol and water as co-solvents on the composition and phenolic content of moringa leaf extracts were evaluated. Six major flavonoids were identified by ultra-high-performance liquid chromatography coupled to a quadrupole-time-of-flight mass spectrometer (UHPLC-Q-ToF-MS). Pressure and temperature had a significant effect on the phenolic composition of the extracts, as well as on their concentrations. The highest concentration of total flavonoids compounds (TFCs) was obtained by using a mixture of CO2 and water of 50:50 (v/v) at 100 bar, at 65 degrees C after a 120 min extraction time that produced a concentration of 11.66 mg +/- 0.02 mg TFC g(-1) sample, which corresponds to 89.0% of the total flavonoids of the sample, obtained by exhaustive extraction.