Selin Şahin

Optimization of olive leaf extract obtained by ultrasound-assisted extraction with response surface methodology.

In the present article, ultrasound-assisted extraction (UAE) of polyphenols from agricultural and industrial waste of olive oil and table oil productions, olive tree (Olea europaea) leaves were investigated. The aim of the study is to examine the extraction parameters such as solvent concentration (0-100% ethanol (EtOH), v/v), the ratio of solid to solvent (25-50mg/mL) and extraction time (20-60 min), and to obtain the best possible combinations of these parameters through response surface methodology (RSM). The extract yield was stated as mg extract per g of dried leaf (DL). Total phenolic content was expressed in gallic acid equivalent (GAE) per g of dried leaf. Free radical scavenging activity for the antioxidant capacity was tested by 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical. The second order polynomial model gave a satisfactory description of the experimental data. 201.2158 mg extract/g DL, 25.0626 mg GAE/g DL, and 95.5610% in respect to inhibition of DPPH radical were predicted at the optimum operating conditions (500 mg solid to 10 mL solvent ratio, 60 min of extraction time and 50% EtOH composition), respectively.

Investigation of Oleuropein Content in Olive Leaf Extract Obtained by Supercritical Fluid Extraction and Soxhlet Methods

The separation processes of the phenolic compounds from solid plant matrixes are of great importance. In the scope of developing more efficient methods to separate olive leaf extract, dried and ground olive tree leaves from Aegean region of Turkey were extracted by means of Soxhlet and supercritical fluid extraction (SFE) methods. In the Soxhlet method, different types of solvents (hexane, water, ethanol, methanol, and methanol/hexane (3:2, v/v) mixture) were used to determine the effect of the solvent type on the extraction performance. In the SFE method, the effect of pressure (100–300 bar), temperature (50 and 100°C), and type of co-solvent on the amount of both extract and oleuropein were investigated. Ethanol, methanol and water were selected as co-solvent in 20% (v/v) amount. Quantitative analysis was performed by using a liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) technique. The results of SFE were compared with those obtained by the Soxhlet method. Whereas the highest oleuropein yield was achieved via the Soxhlet method through methanol with the value of 37.84 mg/g dried leaf, the best oleuropein yield was achieved with the value of 14.26 mg/g dried leaf by using CO2 modified by methanol at 300 bar and 100°C in the SFE method.

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

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.

A novel approach for olive leaf extraction through ultrasound technology : Response surface methodology versus artificial neural networks

Response surface methodology (RSM) and artificial neural network (ANN) were used to evaluate the ultrasound-assisted extraction (UAE) of polyphenols from olive leaves. To investigate the effects of independent parameters on total phenolic content (TPC) in olive leaves, pH (3–11), extraction time (20–60 min), temperature (30–60 °C) and solid/solvent ratio (500 mg/10–20 mL) were selected. RSM and ANN approaches were applied to determine the best possible combinations of these parameters. Box-Behnken design model was chosen for designing the experimental conditions through RSM. The second-order polynomial models gave a satisfactory description of the experimental data. Experimental parameters and responses were used to train the multilayer feed-forward networks with MATLAB. ANN proved to have higher prediction accuracy than that of RSM.

A novel technology for extraction of phenolic antioxidants from mandarin (Citrus deliciosa Tenore) leaves: Solvent-free microwave extraction

Solvent-free microwave extraction (SFME) of polyphenols and flavonoids from mandarin (Citrus deliciosa Tenore) leaves was investigated. A face central composite design (FCCD) through response surface methodology (RSM) was applied to study the effects of extraction time (30–90 sec), microwave irradiation power (250–350 W) and solid mass (2.5–7.5 g), and to optimize the extraction process. The optimum conditions were: extraction time, 53.155 sec; microwave power, 339.190W; and solid mass, 2.500 g. Under the optimum conditions, 0.8610mg-GAE/g-DL of total phenolic content (TPC) and 0.2440mg-CE/g-DL of total flavonoid content (TFC) were extracted. The antioxidant activity of the extracts was assessed by cupric ion reducing antioxidant capacity (CUPRAC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) methods, respectively. Antioxidant values were expressed as mg trolox equivalent antioxidant capacity per gram of dried leaf (mg-TEAC/g-DL). CUPRAC values were highly correlated with both TPC and TFC (r=0.9282/0.8842, P=0.05) in the extracts, whilst DPPH (r=0.7717/0.7435, P=0.05) and ABTS (r=0.6814/0.7072, P=0.05) were relatively less correlated with the same responses.

Study on Oleuropein Extraction from Olive Tree (Olea europaea) Leaves by means of SFE: Comparison of Water and Ethanol as Co-Solvent

The present study focuses on developing methods for olive leaf extraction and deals with obtaining extract, rich in oleuropein, which is the most abundant phenolic compound in olive leaves. Supercritical fluid extraction (SFE) was applied to the dried and ground olive leaves by using CO2 as supercritical (SC) fluid in the presence of water and ethanol as co-solvent. The influences of operating parameters by means of co-solvent content (0-1 mL/min), temperature (50 and 100°C) and pressure (100-300 bar) on both extract and oleuropein yields were investigated. Quantitative analysis was performed by using a liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) technique. The experimental results obtained by using SC-CO2 alone were not satisfactory, and it was seen that addition of a polar modifier is necessary in order to improve yield and selectivity of the process. It was observed that CO2 modified by water and ethanol showed nearly the same extract performance, where CO2 modified by water is better for high oleuropein yield.

Proximate Composition and Nutritional Value of Three Macroalgae: Ascophyllum nodosum, Fucus vesiculosus and Bifurcaria bifurcata

Proximate composition (moisture, protein, lipid and ash content) and nutritional value (fatty acid, amino acid and mineral profile) of three macroalgae (Ascophyllum nodosum, Fucus vesiculosus and Bifurcaria bifurcate) were studied. Chemical composition was significantly (p < 0.001) different among the three seaweeds. In this regard, the B. bifurcata presented the highest fat content (6.54% of dry matter); whereas, F. vesiculosus showed the highest protein level (12.99% dry matter). Regarding fatty acid content, the polyunsaturated fatty acids (PUFAs) were the most abundant followed by saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs). On the other hand, the three seaweeds are a rich source of K (from 3781.35 to 9316.28 mg/100 g), Mn (from 8.28 to 1.96 mg/100 g), Na (from 1836.82 to 4575.71 mg/100 g) and Ca (from 984.73 to 1160.27 mg/100 g). Finally, the most abundant amino acid was glutamic acid (1874.47–1504.53 mg/100 dry matter), followed by aspartic acid (1677.01–800.84 mg/100 g dry matter) and alanine (985.40–655.73 mg/100 g dry matter).

Optimisation of ultrasound‐assisted extraction of rosehip (Rosa canina L.) with response surface methodology

BACKGROUND Ultrasound-assisted extraction of polyphenols from rosehip (Rosa canina L.) was investigated. The aim of the study was to examine the extraction parameters such as extraction time (30-90 min), temperature (30-50 °C) and solvent concentration (40-100% ethanol, v/v), and to obtain the best possible combinations of these parameters by using response surface methodology. RESULTS The experiments were performed according to the face-centred central design. Total phenolic content was expressed in gallic acid equivalent (GAE) per gram of dried matter (DM). The second-order polynomial model gave a satisfactory description of the experimental data. 47.23 mg GAE g(-1) DM was predicted at the optimum operating conditions (40% EtOH composition, 50 °C of temperature, and 81.23 min of extraction time). CONCLUSION All of the parameters (ethanol concentration, extraction time and extraction temperature) used in this research have the significant effect on the extraction efficiency of total phenolic content in rosehip extracts (P < 0.05). The solvent concentration was proved to be the most significant effective on the yields obtained by ultrasound-assisted extraction.

Olive tree (Olea europaea L.) leaf as a waste by‐product of table olive and olive oil industry: a review

Research into finding new uses for by-products of table olive and olive oil industry are of great value not only to the economy but also to the environment where olives are grown and to the human health. Since leaves represent around 10% of the total weight of olives arriving at the mill, it is worth obtaining high added-value compounds from those materials for the preparation of dietary supplements, nutraceuticals, functional food ingredients or cosmeceuticals. In this review article, olive tree (Olea europaea L.) leaf is reviewed as being a potential inexpensive, renewable and abundant source of biophenols. The importance of this agricultural and industrial waste is emphasised by means of describing its availability, nutritional and therapeutic effects and studies conducted on this field.

Effect of olive leaf extract rich in oleuropein on the quality of virgin olive oil

Effect of olive leaf extract rich in oleuropein on the quality of virgin olive oil was investigated. After extracting the dried and ground olive leaves with the assistance of homogenizer, the dried extract was partially dissolved into the oil to increase the oxidative stability of the oil. A face central composite design through response surface methodology was used to investigate the effects of enrichment conditions (extract content, time and mixing speed) on the responses, total phenolic content and oleuropein concentration of the enriched olive oil. Furthermore, antioxidant activity of the oil was determined by 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt method. Additionally, oxidative stability of the enriched oil was assessed by the Rancimat method. Total carotenoid content, peroxide value, α-tocopherol and chlorophyll were also measured, respectively. Addition of 0.15% natural antioxidant increased the stability of the oil (≈46%). The antioxidant capacity of the enriched oil was almost 2.5 times higher than that of the untreated oil. Furthermore, olive leaf extract improved the quality of the virgin olive oil with respect to tocopherol, carotenoid and chlorophyll contents and peroxide value, respectively. The leaf sampling was also performed both in the autumn and summer to evaluate the possible seasonal effects on phenolic profile in order to be careful for selecting the proper harvesting time to apply the extract into the oil.