Statistical mixture design--varimax factor optimization for selective compound extraction from plant material.

Varimax-transformed chromatograms of compounds extracted from Erythrina speciosa Andrews leaves by simplex centroid design mixtures of dichloromethane, hexane, ethanol and acetone are reported and compared with principal component results. Six varimax factors were investigated focusing on the three main groups of extracted compounds with retention times of 1.7, 3.1 and 6.6 min. Varimax models provide chromatographic loading profiles that are simpler than their principal component counterparts. Furthermore varimax score models in terms of extraction medium compositions are simpler to interpret. The first varimax model results in an optimum extraction mixture of 71% dichloromethane-29% acetone although substitution of acetone by ethanol results in an almost identical extraction profile. The second varimax score model predicts optimum extraction binary mixtures with hexane proportions ranging from 50 to 100% for complementary proportions of either acetone or ethanol. The third varimax factor provides a response surface that is very similar to the one found for the third PC. Confirmatory experiments were performed to validate the model predictions.