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Comparative Study
. 2017 Jun 24;22(7):1056.
doi: 10.3390/molecules22071056.

Solvent-Free Microwave-Assisted Extraction of Polyphenols from Olive Tree Leaves: Antioxidant and Antimicrobial Properties

Selin Şahin  1 , Ruya Samli  2 , Ayşe Seher Birteksöz Tan  3 , Francisco J Barba  4 , Farid Chemat  5 , Giancarlo Cravotto  6 , José M Lorenzo  7
Affiliations
Comparative Study

Solvent-Free Microwave-Assisted Extraction of Polyphenols from Olive Tree Leaves: Antioxidant and Antimicrobial Properties

Selin Şahin et al. Molecules. .

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 (Oleaeuropaea) 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.

Keywords: antimicrobial; antioxidant; oleuropein; olive leaves; optimization; solvent-free microwave extraction.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Response surface plot for the TPC (a) and oleuropein (b) from olive leaf extract as a function of microwave irradiation power to solid mass (extraction time = 2.5 min).
Figure 2
Figure 2
Response surface plot for the TPC (a) and oleuropein (b) from olive leaf extract as a function of extraction time to solid mass (microwave irradiation power = 300 W).
Figure 3
Figure 3
Response surface plot for the TPC (a) and oleuropein (b) from olive leaf extract as a function of extraction time to microwave irradiation power (solid mass = 7.5 g).
Figure 4
Figure 4
The feed-forward multilayer artificial neural network model with a back-propagation learning algorithm.
Figure 5
Figure 5
Reactor for solvent-free microwave-assisted extraction.
Figure 6
Figure 6
A typical chromatogram of individual polyphenol composition in olive leaf extracts.
See this image and copyright information in PMC

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