Journal of Pharmaceutical Research International

This study establishes a reproducible laboratory-scale framework combining a defined deep eutectic solvent with supercritical carbon dioxide for the selective recovery of kavalactones from dried roots of Piper methysticum. Baseline total kavalactone content, determined by exhaustive ethanol extraction and validated ultra-high-performance liquid chromatography, was 9.15 ± 0.28% w/w on a dry basis, equivalent to 91.5 ± 2.8 g per kg of dry root. A choline chloride and urea deep eutectic solvent at a 1:2 molar ratio was prepared with a water content of 0.42 ± 0.05% w/w, a density of 1.21 g per mL at 25°C, and a viscosity of 412 mPa·s at 25°C. Formation of a homogeneous liquid with a depressed melting point consistent with literature-reported choline chloride and urea 1:2 systems was taken as indicative of eutectic formation. No Fourier transform infrared spectroscopy was performed for hydrogen-bond confirmation in this study. The deep eutectic solvent was formulated as a modifier solution of 30% deep eutectic solvent and 70% anhydrous ethanol, delivered at 0.6 g per min against a carbon dioxide flow of 20 g per min, corresponding to 3.0% w/w modifier relative to carbon dioxide and 0.9% w/w net deep eutectic solvent relative to carbon dioxide. Processing 1.0 kg batches as four sequential loadings of 250 g each, with one hour per loading and four hours cumulatively per batch, was evaluated at 250 bar and 60°C in vessel 1 and 150 bar and 45°C in vessel 2. Four conditions were compared in triplicate, with three independent batches per condition. The optimised deep eutectic solvent modifier supercritical carbon dioxide condition yielded 11.2 ± 0.38% w/w oleoresin, equivalent to 112 ± 3.8 g per kg, containing 69.5 ± 1.8% w/w total kavalactones, corresponding to 77.8 ± 2.6 g per kg root and 85.0 ± 4.2% recovery of baseline. Residual kavalactones in spent biomass were 8.2 ± 0.9 g per kg, giving total accountability of 86.0 g per kg, or 94.0% of baseline. Comparative controls gave 32.7 g per kg with 35.7% recovery for supercritical carbon dioxide only, 62.5 g per kg with 68.3% recovery for supercritical carbon dioxide plus 10% ethanol, and 58.4 g per kg with 63.8% recovery for deep eutectic solvent alone. The hybrid process improved recovery by 24.5% over the ethanol control, with statistical significance shown by analysis of variance, F (3,8) equal to 38.7, p less than 0.0001, and Tukey p equal to 0.0032. Six kavalactones were resolved within 16 min with resolution greater than 1.5 using UHPLC with photodiode-array detection at 220 nm.