Conventional Solid Extraction Research Articles

Evaluation and comparison in caffeine extraction under green conditions: Solvent selection and ultrasound‐assisted process

AbstractThis study compared the green solvents ethyl acetate and water for caffeine extraction from coffee pills against four traditional solvents (ethanol, methanol, acetone, and acetonitrile). Each solvent's green degree (GD) was calculated using seven environmental and technical performance parameters. The environmental parameters were obtained from the Glaxo Smith Kline guide. Fick's law of effective diffusion was used as the technical parameter. Water was selected as the preferred solvent (among the six evaluated in this study), and its ultrasound‐assisted extraction (UAE) conditions were optimized. The optimal conditions were estimated by ridge analysis. It was found that caffeine extraction was approximately 4.3 times higher in UAE than in conventional solid–liquid processes, and the extraction time was reduced by 96%. Moreover, this process improved caffeine extraction with water. Therefore, the use of UAE over conventional solid extraction and water as an inexpensive, easily accessible, manageable, and environmentally friendly solvent provides extraction alternatives for caffeine in different matrices. Additionally, a methodology is proposed to evaluate the GD for each solvent in the green chemistry framework to achieve sustainable development goals.

Optimization of Ultrasonic-Assisted Extraction of Major Phenolic Compounds from Olive Leaves (Olea europaea L.) Using Response Surface Methodology.

The ultrasound-assisted extraction (UAE) of oleuropein (OLE), verbascoside (VER), and luteolin-4′-O-glucoside (L4OG), as the major phenolics from olive leaves, was optimized using response surface methodology (RSM). A Box–Behnken design (BBD) was used to monitor the effect of different modes of ultrasound operation (pulsed and continuous), liquid–solid (L–S) ratio, and sonication time on each phenolic yield. The yield of UAE and conventional solid extraction (CSE) was determined after performing ultrahigh-performance liquid chromatography with a diode-array detector (UHPLC-DAD) analysis on the extracts. The results suggested that, under optimal conditions, the concentrations of OLE, VER, and L4OG were 13.386, 0.363, and 0.527 mg/g of dry powdered olive leaves (DPOL), respectively. Verification of experiments was carried out under the modified optimal conditions and the relative errors between the predicted and experimental values were dependent on the examined phenolic compound (OLE 8.63%, VER 11.3%, and L4OG 22.48%). In comparison with CSE, UAE improved the yields of OLE, VER, and L4OG (32.6%, 41.8%, and 47.5%, respectively, after 1 min) at a temperature of 60 °C, an L–S ratio of 15 (v/w), and in the continuous mode of UAE. We demonstrated that the UAE technique is an efficient method for enhancing yields of OLE, VER, and L4OG in olive-leaf extracts, while the chosen model was adequate to optimize the extraction of major phenolic compounds from olive leaves.