Optimization of chemometric approaches for the extraction of isorhamnetin-3-O-rutinoside from Calendula officinalis L

The application of Design of Experiments (DoE) to the determination of optimum conditions for an extraction process relies on the correct selection of mathematical models. The linear model is the one typically used; however, in some cases it does not always have superior performance, ignoring the real nature of the data and its appropriate descriptive model. In order to evaluate the extraction efficiency of isorhamnetin-3-O-rutinoside from flowers of Calendula officinalis L. a multivariate factorial analysis was used. Simulations were conducted using linear, quadratic, full cubic and special cubic models. A Simplex-Centroid design was chosen as it delivered greater precision with only minor errors versus other models tested. Analyses were performed by capillary zone electrophoresis using sodium tetraborate buffer (40mmolL(-1), pH 9.4) containing 10% methanol. The detection was linear over a range of 8.0-50.0mgL(-1) (r(2)=0.996), and the limits of detection (LOD) and quantification (LOQ) for isorhamnetin-3-O-rutinoside were 3.44mgL(-1) and 11.47mgL(-1), respectively. The full cubic model showed the best extraction results, with an error of 3.40% compared to analysis of variance, and a determination coefficient of 0.974. The difference between the responses at the reference point, calculated by the model, and the experimental response, varies around 2.72% for full cubic model. Comparison of the four models showed the full cubic model was the most appropriate one, allowing greater efficiency in the extraction of isorhamnetin-3-O-rutinoside. Selection of the model made it possible to obtain a 60% increase in sensitivity compared to the linear model.