Optimization of the extraction process of minerals from Salvia officinalis L. using factorial design methodology

The extraction of minerals from garden sage (Salvia officinalis L.) using water as a solvent was studied at different extraction conditions. A full factorial experiment 2(3) with replication was performed. The effects of three extraction factors, liquid/solid ratio (15 and 30 mL/g solvent volume per g of raw material), extraction temperature (40 and 100 degrees C) and extraction time (20 and 80 min) such as their interaction were evaluated by the analysis of variance and linear regression model. At the 95% confidence level all three factors were effective on Na, K, Mg, Ca, Fe, Cu, Mn, Zn, Ni, Cr and Al yields, the most important factor being the extraction time (except for Ca, Cr and Al). All regression models gave a good fit to the experimental data (R-2 > 99%). The content of minerals in water extracts were determined using inductively-coupled plasma atomic emission spectrometry. The optimum extraction conditions were as follows: liquid/solid ratio 15 mL/g, extraction temperature 100 degrees C, and extraction time 80 min. The data obtained were used to establish the thermodynamics of the extraction process. The Gibbs free energy change for the extraction of minerals is negative (except for Fe, Al and Cr), indicating that the process is feasible and spontaneous.