Determination of reducing power of 56 Algerian plant products using olive (Olea europaea) oil as extraction solvent

Abstract

This work evaluates the efficiency of olive (Olea europaea) oil (OO) as extraction solvent (referred to here as lipophilic extraction) for reducing power (RP) determination of 56 plant materials belonging to three plant product groups: medicinal plant leaves, fruit peels and green vegetable pulps. In addition, the sample which exhibited the greatest lipophilic RP (RPlip) value in each studied group was characterized in terms of (1) RPaq in the case of an aqueous extraction, (2) Pearson’s correlation coefficient (r) between RP values and color parameters of CIELab system, in the case of both lipophilic and aqueous extraction, and (3) diphenylpicrylhydrazyl (DPPH) radical scavenging activity (RSA) in the case of both lipophilic and aqueous extraction. Among all investigated plant products, the wormwood (Artemisia absinthium) leaves showed the highest RPlip (∼70 mg BHT equivalents(eq.) × g−1 dry weight (dw)), while among fruits and green vegetables, the arbutus-berries (Arbutus unedo) peel (∼53 mg BHT eq. × g−1 wet weight (ww)) and eggplant (Solanum melongena) pulp (30 mg BHT eq. × g−1, ww) gave the best results, respectively. Nevertheless, RPlip negative values were obtained in numerous investigated samples. Regarding the additional characterization, any significant correlation was found between RPlip and color parameters, whereas a significant perfect positive correlation (p ≤ 0.05, r ∼ 1) was found between RPaq and certain color parameters in the case of arbutus-berries and eggplant. Furthermore, the RSA results confirmed the predominance of wormwood lipophilic extract in terms of antioxidant potential. Considering the applied lipidic extraction procedure, the resulting data reflect the antioxidant potential of OO-based plant infusions.