Supercritical fluid extraction and characterisation of Moringa oleifera leaves oil

Abstract

This work was aimed to extract and characterise the Moringa oleifera leaves oils using supercritical fluid extraction (SFE) and to compare the results against those obtained using the conventional Soxhlet extraction method. The oils extracted were analysed using GC–MS. The compounds were identified according to their retention indices and mass spectra (EI, 70eV). The effects of pressure (30MPa, 40MPa, 50MPa), temperature (40°C, 60°C, 80°C) and extraction time (60min, 90min and 120min) on the oil yield were investigated using a three-level orthogonal array design. The experimental results showed that while the oil yield increased with increasing any of the three parameters, temperature had the most significant effect. The highest yield of 6.34% was obtained under the condition of pressure 50MPa, temperature 60°C and an extraction time of 120min. The Soxhlet extraction was performed at 78°C for 8h using hexane as the solvent. A total of 42 compounds were identified in the Soxhlet extracted oil while only 12 compounds were detected in the SFE extracted oil. Some compounds that were found in the Soxhlet extracts were not detected in the SFE samples. This is because the supercritical fluid extraction is more selective than the Soxhlet extraction method. The compositions of the oil extracted by SFE under the different conditions examined were mostly similar and the major compounds identified were 1,2-Benzenedicarboxylic acid, mono (2-ethylhexyl) ester, nonacosane, heptacosane, β-Amyrin, although their quantities differed.