Application of Experimental Methods in Fluid Mechanics and Energetics in the Extraction of Medicinal Plants

Fluid mechanics and energetics are crucial for optimizing modern extraction methods, such as microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE), which are used for natural products. These modern techniques offer advantages over conventional methods by reducing extraction time, energy consumption, and solvent usage. The article highlights the importance of Design of Experiments (DOE) for systematically optimizing parameters, improving extract quality, and increasing yields, ultimately leading to sustainable production of high- quality natural products. The article analyzes in detail common extraction techniques such as Soxhlet extraction, maceration, percolation and decoction. We list their main disadvantages, which include long extraction times, high solvent and energy consumption, and the risk of decomposition of heat-sensitive compounds. We then focus on unconventional methods. We explain that MAE uses electromagnetic waves to directly heat and break down plant cells. UAE, on the other hand, uses acoustic energy to create cavitation bubbles, which leads to disruption of the cell structure and better penetration of the solvent into the material. This paper emphasizes the key role of Design of Experiments (DOE). It describes in detail its principles and steps, from screening designs (e.g. fractional factorial design, Plackett- Burman design) to identify the most important variables to optimization designs (e.g. Box-Behnken design, central composite design) to determine the optimal levels of these variables. The article concludes with successful examples of DOE use in UAE optimization for various medicinal plants. These examples confirm that such optimized procedures yield better extract quality, higher yields, and stronger biological activities compared to traditional methods.