Optimization of Soxhlet extraction conditions and preliminary phytochemical characterization of Urtica dioica leaf extract using response surface methodology

Plant-derived extracts are increasingly investigated as potential sources of environmentally compatible compounds for agricultural applications. However, extraction efficiency depends strongly on process conditions, and information on optimized extraction of Ethiopian Urtica dioica leaves remains limited. This study aimed to optimize Soxhlet extraction conditions for U. dioica leaves using Response Surface Methodology (RSM) and to provide preliminary physicochemical and phytochemical characterization of the resulting extract. A Central Composite Design (CCD) was used to evaluate the effects of extraction temperature (50–70 °C), extraction time (3–5 h), and solid-to-solvent ratio (0.125–0.1875 g/mL) on extraction yield. The quadratic model was statistically significant ( p < 0.0001), with a non-significant lack of fit ( p = 0.0749). Numerical optimization predicted optimum conditions of 64.62 °C, 3.01 h, and 0.139 g/mL, giving a predicted extraction yield of 0.330% (w/w). FTIR and TLC analyses provided preliminary evidence of diverse functional groups and multiple chromatographic fractions in the extract. These findings establish an optimized laboratory-scale extraction condition and a preliminary chemical profile for Ethiopian U. dioica leaves. Clinical trial number: Not applicable.