Optimization of a sustainable purification protocol for lutein and chlorophyll from spinach by-products by a saponification procedure using Box Behnken design and desirability function

Abstract The objective of this study was to develop a safe and ecologically sustainable protocol, to extract and separate lutein and chlorophyll from spinach discards. A saponification in an aqueous medium was carried out to release the phytyl aliphatic chain from the porphyrin ring of chlorophyll. Polar chlorophyll derivatives were formed, remaining in the aqueous medium, whereas apolar lutein remaining in the plant residues and was extracted thereafter by maceration in 95% ethanol. However, the saponification step may cause a significant degradation of lutein, resulting in low extraction yields. The saponification parameters were studied using response surface methodology to determine the conditions providing the highest recovery of lutein in an ethanolic extract, combined with the lowest loss of chlorophyll derivatives. Through this procedure, using the Derringer’s desirability function, we uncovered that the optimal conditions for saponification were 16 h of aqueous maceration with 3.9% (W/V) sodium hydroxide at 60 °C. This procedure can be easily scaled for high volume commercial extraction of these compounds.