Optimizacija i modelovanje kinetike ekstrakcije rezinoida i mineralnih materija iz belog ivanjskog cveća (Galium mollugo L.)

Abstract

This doctoral dissertation deals with the extraction of total extractive (resinoid) and some minerals (potassium, calcium and magnesium) from ground, dried aerial parts of white lady’s bedstraw (Galium mollugo L.) using an aqueous ethanolic solution (50 % vol.) at the solvent-to-plant material ratio of 20 g/g and different temperatures. Both maceration and indirect ultrasound-assisted extraction were employed. The main goals were the optimization, kinetic modeling and thermodynamic analysis of the maceration and ultrasound-assisted extraction of resinoid and minerals from aerial parts of G. mollugo. For the purpose of modeling the extraction conditions, the relationships of resinoid and the minerals on extraction temperature and extraction time were modeled by using the parametric response surface methodology (RSM) in the form of a quadratic equation and the non-parametric method of artificial neural network (ANN). Both models were found acceptable for predicting yields of resinoid and the minerals in the temperature ranges of 23-80 oC and 23-40 oC, respectively. However, having higher values of coefficient of determination ( R2 ) and smaller values of mean relative percentage deviation (MRPD), the ANN model appears to be better than the quadratic equation, but the latter model is more reliable in predicting the yields within the applied temperature ranges. The RSM showed that both temperature and time had a statistically significant impact on yields of resinoid and the minerals at the 95% confidence level, extraction temperature being more significant than extraction time. To maximize the yield of resinoid and minerals the extraction conditions were optimized by using the quadratic model and the combination of the ANN coupled with a genetic algorithm (GA). Maximum yields of resinoid and minerals predicted by the two models are very close to each other and agree with the corresponding actual maximum v yields. Also, both models provide similar optimal extraction conditions for both techniques applied. According to the ANN-GA model, the optimal extraction conditions (80 oC and 190 min for maceration and 40 oC and 56 min for ultrasound-assisted extraction) maximized the resinoid yields to 21.3 and 26.0 g/100 g, respectively which agree with the actual maximum resinoid yields (20.8 i 25.7 g/100 g) achieved under the same extraction conditions. The optimal extraction conditions as well as the maximum yield and extraction selectivity of minerals depended on the extraction technique and the type of mineral. For both techniques applied, the extraction selectivity of the minerals decreased with increasing temperature. At a constant temperature, the higher mineral extraction selectivity was achieved by maceration than by ultrasound-assisted extraction. The extraction of resinoid and minerals from aerial parts of G. mollugo by the aqueous ethanolic solution in the absence of ultrasound than in its presence includes two simultaneous processes, namely washing and diffusion of extractive matters. This mechanism was assumed in modeling the kinetics of resinoid and minerals extraction through the phenomenological model. The derived kinetic models for resinoid and minerals are reliable and accurate in representing the variations of resinoid and minerals yields with time at different temperatures in the absence and the presence of ultrasound. The parameters of the models depend on the extraction technique, temperature, the type of plant material and the type of extractive matters. Ultrasound affects the washing of resinoid and minerals but not the diffusion of extractive matters through plant particles. The thermodynamic analysis of resinoid and minerals extraction from aerial parts of G. mollugo shows that both maceration and ultrasound-assisted extraction are spontaneous, irreversible and endothermic. Spontaneity of resinoid and mineral extraction is favored by increasing the extraction temperature. The higher extraction degree in the presence of ultrasound is explained by the increased change of entropy of the extraction system. The minerals yield increased by a factor of 1.02–1.06 and 1.14–1.27 in the absence and the presence of ultrasound, respectively for every 10 oC rise in temperature. vi Based on the higher maximum yields of resinoid and minerals, the lower extraction temperature and the shorter extraction time ultrasound-assisted extraction is more favorable than maceration. However, resinoid obtained in the presence of ultrasound shows lower antioxidative activity. Also, ultrasound-assisted extraction is characterazed by poorer extraction selectivity of minerals. Furthermore, ultrasonic extractors are more complex and more expensive than extractors for maceration. Therefore, further investigations and techno-economic analysis are needed to choose the better technique for resinoid and mineral extraction from aeruial parts of G. mollugo.