Ultrasonic- and microwave-assisted extraction of curcuminoids and cyclodextrin complexes of curcumin from C. domestica Val.

Abstract

This study investigates the isolation of curcuminoids from Curcuma domestica Val. using ultrasonic-assisted extraction (UAE), microwave-assisted extraction (MAE) compared with conventional cold solvent extraction method and the use of inclusion complexation of curcumin with methyl-?-cyclodextrin (Mß-CD) for improving their solubility. The extractions were optimized by determining the content of three curcuminoid markers, namely curcumin (C), demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC). The extraction efficiencies were compared in terms of extraction time, sample through-put and solvent consumption. The optimized parameters for UAE of curcuminoids were extraction amplitude of 100, particle size of 0.30-0.60 mm, extraction time of 20 min, extraction solvent volume of 10 mL and extraction temperature of 60°C. Meanwhile, the relative recoveries (RRs) for aqueous extraction were in the range of 91.59-98.99%, 89.79- 94.95% and 89.33-94.77% for C, DMC and BDMC, respectively. Although UAE using methanol resulted in a slightly higher extraction yield and shorter extraction time compared to those using water, both methods showed similar pattern of results. Despite these, water is cost effective, safe and environmentally friendly. These advantages of aqueous solvent can be used as a yard stick to substitute organic solvents for UAE of curcuminoids from C. domestica. At maximum set energy, the MAE optimum extraction parameters were particle size of 0.30-0.60 mm, extraction time of 3 min, extraction solvent volume of 10 mL and extraction temperature of 60°C with RRs of 92.48-99.44%, 90.58-97.43% and 90.03-96.07% for C, DMC and BDMC, respectively. Both UAE and MAE applications showed remarkable improvements in terms of extraction time, solvent consumption, extraction yield and the quality of extracts compared to conventional cold solvent extractions method. However, as compared to UAE, the optimized MAE application was better in term of quantity of curcuminoids. MAE is also simpler, faster, more efficient approach and allows the possibility of simultaneous multiple extractions. The inclusion complex formed using Mß-CD with the application of MAE was more stable than that with UAE based on the stability constant (KC) values of 213.08 M-1 and 515.19 M-1, for UAE and MAE, respectively. Results from characterization of the inclusion complex with scanning electron microscope showed that co-precipitation method was best for UAE while all of the mixing methods can be used for the inclusion complexation with MAE application. The kneading and co-precipitation methods were found to be the best for the inclusion complexation between turmeric rhizome oleoresins and Mß- CD in UAE, while all of the mixing methods were found to be suitable for inclusion complexation of turmeric rhizome oleoresins with Mß-CD in MAE as indicated by Fourier transform infrared spectroscopy