Abstract
Response surface methodology (RSM) and artificial neural networks (ANN) were evaluated and compared in order to decide which method was the most appropriate to predict and optimize total phenolic content (TPC) and oleuropein yields in olive tree leaf (Olea europaea) extracts, obtained after solvent-free microwave-assisted extraction (SFMAE). The SFMAE processing conditions were: microwave irradiation power 250–350 W, extraction time 2–3 min, and the amount of sample 5–10 g. Furthermore, the antioxidant and antimicrobial activities of the olive leaf extracts, obtained under optimal extraction conditions, were assessed by several in vitro assays. ANN had better prediction performance for TPC and oleuropein yields compared to RSM. The optimum extraction conditions to recover both TPC and oleuropein were: irradiation power 250 W, extraction time 2 min, and amount of sample 5 g, independent of the method used for prediction. Under these conditions, the maximal yield of oleuropein (0.060 ± 0.012 ppm) was obtained and the amount of TPC was 2.480 ± 0.060 ppm. Moreover, olive leaf extracts obtained under optimum SFMAE conditions showed antibacterial activity against S. aureus and S. epidermidis, with a minimum inhibitory concentration (MIC) value of 1.25 mg/mL.
Highlights
Olive trees come from a genus of evergreen trees in the family Oleaceae, which contains 24 genera and 900 species [1]
Olive leaves and cakes have been traditionally used for animal feeding, but they can be used in other applications due to their high content of high added-value compounds with antioxidant and antimicrobial properties [2,4,5]
Two different types of modelling methods (RSM and artificial neural networks (ANN)) were applied to study, predict, and estimate the behaviour of total phenolic content (TPC) and oleuropein in olive leaf extracts obtained by solvent-free microwave-assisted extraction (SFMAE)
Summary
Olive trees come from a genus of evergreen trees in the family Oleaceae, which contains 24 genera and 900 species [1]. Olive leaves and cakes have been traditionally used for animal feeding, but they can be used in other applications (e.g., food additives, nutraceuticals, and pharmaceutical and cosmetic purposes) due to their high content of high added-value compounds with antioxidant and antimicrobial properties (e.g., vitamins, polyphenols, minerals, etc.) [2,4,5]. In this regard, Bouaziz et al [6]. Increased interest has been shown to the recovery of phenolic compounds from olive leaves [5,7,8]
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