Genetic algorithm coupled Box-Behnken design-based optimization of ultrasound-assisted xanthophyll extraction from marigold (Tagetes erecta L.): process intensification, profiling, and antioxidant activities

Optimization of the extraction process for natural compounds aims to obtain the maximum feasible yield quickly using the least amount of solvent. A single-step ultrasonic probe-assisted extraction (UPE) technique was observed to be superior compared to the exhaustive conventional and ultrasonic bath extraction for xanthophyll pigments from a hybrid genotype (DAMH-39) of African marigold (Tagetes erecta L.) in terms of less time and solvent requirement. The process variables of the UPE technique were optimized using a Box-Behnken design (BBD) of response surface methodology (RSM) followed by fine-tuning of the model using an artificial intelligence-based genetic algorithm (GA) for the maximum output of the response variable, i.e., the total xanthophyll yield. The GA-coupled RSM model predicted the optimum values of the process variables as 31.38 mL g(-1) solvent-to-solid ratio, 56.56% ultrasonication amplitude, and 30 min of ultrasonication time for a maximum xanthophyll yield of 13.35 mg g(-1), which was very close to the result of validation experiment (13.10 mg g(-1)) with a calculated error value of only 1.88%. The quality of the extracted xanthophylls by the hybrid model-optimized method was found to be superior as compared to the exhaustive techniques. However, no significant differences were observed in the antioxidant activities of the extracts obtained by different extraction techniques due to the possible interferences from the co-extractives. Analysis of the chemical constituents of the xanthophyll extract confirmed the presence of lutein linoleate, an unsaturated fatty ester of lutein for the first time in marigold along with five monoesters and three diesters of lutein, and two diesters of violaxanthin. The study signified the potential of the RSM-GA hybrid model for process optimization of extraction of natural compounds.