A novel extraction of polyphenols, flavonoids and tannins obtained from Argania Spinosa hulls: Modeling and optimization of the process using the response surface methodology

Response surface methodology (RSM) modelling was used for estimation of predictive total polyphenols content (TPC), total flavonoid content (TFC) and total tannin content (TTC) obtained from Moroccan Argan (Argania Spinosa) hulls. A 3-level 3-factor central composite design was used to optimize microwave-assisted Soxhlet extraction (MASE) to obtain maximum yield of target responses as a function of extraction time (t: 15–35 min), solvent composition ethanol:wather (C: 10–0%) and microwave power (P: 400–800 W). Maximum compounds of the three output parameters: 129,95 mg gallic acid equivalents/g dry weight TPC yield, 10,24 mg rutin equivalents/g dry weight TFC yield, and 76,95 mg gallic acid equivalents/g dry weight TTC, were obtained under optimum extraction conditions of t=35min, C=23%, and P=600W for the TPC and t=35 min, C=10%, and P=600W for the TFC and finally t=35min, C=22,8%, and P=600W for the TTC. For each experiment, the total polyphenolic contents, the total flavonoid contents and the total tannin contents were quantified using colorimetric essays. A significant effect of power extraction and solvent composition was proved by ANOVA. RSM applied in MASE, permitted to develop a solvent-minimized extraction process of polyphenols, flavonoids and tannins, using lower proportion of a green solvent with a shortest extraction time and in the same time to improve the quantity of extracts obtained from a natural resource.