Kinetic properties on supercritical carbon dioxide extraction of charantin from Momordica charantia L. with co-extractant

Abstract

Charantin is a bioactive compound in bitter gourd (Momordica charantia) fruit that has been claimed to be able to lower blood glucose level in type 2 diabetes mellitus patient. Its unique dual polarity compound and larger molecular weight makes it difficult to be extracted using conventional extraction method such as Soxhlet and water extraction. The aim of this study is to extract charantin from Momordica charantia using supercritical carbon dioxide (SC-CO2) in the presence of absolute ethanol as co-extractant (1:3 w/v feed-to-solvent ratio). As mean particle size influences the extraction yield, its effects were investigated in the range of 0.2-0.7 mm and validated using the extraction curve model. The optimum extraction pressure and temperature ranging from 10-30 MPa and 45-65 oC respectively were determined using response surface methodology with 3-level factorial while the effect of SC-CO2 operating conditions and kinetic properties on the extraction yield were validated using the kinetic models of Barton, Crank, simplified linear driving force (SLDF) and Sovová. Results demonstrated that the extraction efficiency of charantin was found to be 13.25 x 10-3 mg ch/g CO2 with the highest concentration of charantin of 112.56 mg/100 g dry weight at optimum condition of 0.3 mm particle size, 30 MPa pressure, 65 oC temperature and 5 mL/min flowrate. The highest extraction yield of 42.4 mg/g gave the highest diffusion coefficient (De) value of 16.49 x 10-12 m2/s, with percentage deviation error of 4.48% at 30 MPa and 55 oC using the Crank model. Additionally, the mass transfer coefficient in the fluid phase (kf) was 4.28 x 10-6 m/s and overall mass transfer coefficient (kp) was 4.87 x 10-7 m/s obtained by SLDF model with experimental solubility (ys) of 2.8 g/kg CO2. The SC-CO2 extraction with co-extractant has been demonstrated to be a promising technique to extract the highly valued charantin compound producing a novel product for nutraceutical and pharmaceutical industries.