Solubility of azadirachtin and several triterpenoid compounds extracted from neem seed kernel in supercritical CO2

The extraction of oil and several triterpenoid compounds (azadirachtin, nimbin, and salannin) from need seed kernel by supercritical CO2 (SC-CO2) was demonstrated in this work. The experiments were performed with variation of pressures from 10 MPa to 35 MPa and temperatures (313.15 K, 323.15 K, and 333.15 K) for 4 h with CO2 flow rate of 5 mL/min (measured at 6.8 MPa, 303.15 K). The amounts of neem oil, azadirachtin, nimbin, and salannin extracted were increased with increasing pressure and temperature. The solubility of neem oil and triterpenoids studied was presented as a function of temperature and solvating power of CO2 in 3D mesh plots. The Chrastil and Mendez-Santiago and Teja density-based models were applied to evaluate experimental data. The heat of solution (ΔH) of neem oil, azadirachtin, nimbin, and salannin in SC-CO2 was found to be −28.79 kJ/mol, −42.33 kJ/mol, −35.98 kJ/mol, and −51.69 kJ/mol, respectively. The consistency plots of Mendez-Santiago and Teja model were given to test its applicability in representing experimental data over a range of pressure and temperature studied.