Chemometric study for the performances of deep eutectic solvents during the recovery of high-added-value substances from Moringa oleifera leaves: Principal component analysis.

Introduction: Moringa oleifera is a plant with high antioxidant content in its leaves, flowers and seeds. It attracts the attention of researchers with the effect of its nutritional and medical advantages.

Objective: The purpose of the current study is to propose a deep eutectic solvent (DES)-based ultrasound-assisted extraction of bioactive substances from M. oleifera leaves by the application of a chemometric study.

Methodology: A total of 18 different choline chloride-based DESs were prepared by using several hydrogen bond donors (glucose, sucrose, glycerol, ethylene glycol, urea and dimethyl urea) with various molar ratios (1:1, 1:2 and 2:1) by addition of diluents (water and 50% methanol) or alone. In order to decide the best DES combination, principal component analysis (PCA) was applied. The response surface method (RSM) was used as statistical experimental design approach through the Box-Behnken design.

Results: The best phenolic (TPC), flavonoid (TFC) and antioxidant activity yields of M. oleifera leaf extract were found to be 19.102 mg-GAE, 10.47 mg-CE and 24.404 mg-TEAC per gram dried leaf under the optimal conditions (50% water content, 20% amplitude, 15 min time). The model fitting has been also found reliable depending on the statistical indicators such as p-value (<0.0001), coefficients of determination (R² = 0.9827, 0.9916 and 0.9864) and root mean square error (RMSE = 1.0562, 2.4656 and 0.7713).

Conclusions: A chemometric study through PCA was carried out to determine the similarities and differences between the solvent groups, and the ethylene glycol-based DES (1:2, molar ratio) with the addition of water showed the best performance.