Development and validation of an HPLC-DAD method for determination of oleuropein and other bioactive compounds, in olive leaf by-products.

BACKGROUND Oil mills could benefit preparing their own aqueous extracts from olive leaves, so our aim was to measure the bioactive compounds richness of such extracts, specially oleuropein. A water-based microwave extraction procedure was developed and a selective and precise HPLC-DAD method for the determination of oleuropein and others bioactive compounds from olive leaves was validated. RESULTS The water solubility of oleuropein was determined, resulting in 9.5 g L-1 . The extraction procedure was optimized in terms of power, olive leaf weight/water volume ratio and time of extraction, and the results revealed that 2 mg mL-1 and a microwave irradiation at 800 W for 30 s were the most efficient. Oleuropein was determined by the new validation method, which showed good linearity (R2  = 0.996), precision (%RSD < 10%), recovery (118.6%) and limits of detection (17.48 mg L-1 ) and quantification (21.54 mg L-1 ). Good correlation (R2  = 0.979) was obtained between oleuropein of the olive leaf extracts determined by HPLC-DAD and by UV-visible spectrophotometry. CONCLUSION A simple extraction method was developed and validated to obtain aqueous extract from olive leaves by microwave extraction, determining for the first time oleuropein water solubility. Method validation showed that oleuropein in olive leaves could be quantified when it is at least 1% dry weight by means of HPLC-DAD. The UV-visible spectrophotometry can be useful in the oil mills because will be possible to determine in situ the oleuropein and other bioactive compounds content of such leaf aqueous extracts. This article is protected by copyright. All rights reserved.

[1]  M. Tsimidou,et al.  Bioactive ingredients in olive leaves , 2021, Olives and Olive Oil in Health and Disease Prevention.

[2]  J. Pedraz,et al.  Development and validation of an eco-friendly HPLC-DAD method for the determination of oleuropein and its applicability to several matrices: olive oil, olive leaf extracts and nanostructured lipid carriers , 2020 .

[3]  I. Hussain,et al.  Phytochemical composition, antioxidant and antimicrobial activities of leaves of Olea europaea wild variety , 2019, Journal of Food Measurement and Characterization.

[4]  María del Mar Contreras,et al.  Extraction of oleuropein and luteolin-7-O-glucoside from olive leaves: Optimization of technique and operating conditions. , 2019, Food chemistry.

[5]  A. Cassano,et al.  Eco-Friendly Extraction and Characterisation of Nutraceuticals from Olive Leaves , 2019, Molecules.

[6]  E. Medina,et al.  Characterization of bioactive compounds in commercial olive leaf extracts, and olive leaves and their infusions. , 2019, Food & function.

[7]  M. Merzouki,et al.  Phenolic profile (HPLC-UV) of olive leaves according to extraction procedure and assessment of antibacterial activity , 2019, Biotechnology reports.

[8]  A. Magnani,et al.  Chemical characterization of liposomes containing nutraceutical compounds: Tyrosol, hydroxytyrosol and oleuropein. , 2019, Biophysical chemistry.

[9]  A. Zinnai,et al.  Olive Leaf Addition Increases Olive Oil Nutraceutical Properties , 2019, Molecules.

[10]  J. V. García-Pérez,et al.  From extraction of valuable compounds to health promoting benefits of olive leaves through bioaccessibility, bioavailability and impact on gut microbiota , 2019, Trends in Food Science & Technology.

[11]  V. T. Papoti,et al.  Screening Olive Leaves from Unexploited Traditional Greek Cultivars for Their Phenolic Antioxidant Dynamic , 2018, Foods.

[12]  J. Lorenzo,et al.  Effect of drying method on oleuropein, total phenolic content, flavonoid content, and antioxidant activity of olive (Olea europaea) leaf , 2018 .

[13]  S. Sahin,et al.  Effect of olive leaf extract rich in oleuropein on the quality of virgin olive oil , 2017, Journal of Food Science and Technology.

[14]  E. Medina,et al.  Quantification of bioactive compounds in Picual and Arbequina olive leaves and fruit. , 2017, Journal of the science of food and agriculture.

[15]  J. Castellano,et al.  Determination of major bioactive compounds from olive leaf , 2015 .

[16]  S. Jafari,et al.  Bioactive profile, dehydration, extraction and application of the bioactive components of olive leaves , 2015 .

[17]  A. Zalacain,et al.  Vine-shoot waste aqueous extracts for re-use in agriculture obtained by different extraction techniques: phenolic, volatile, and mineral compounds. , 2014, Journal of agricultural and food chemistry.

[18]  F. Al-Rimawi,et al.  Optimum Conditions for Oleuropein Extraction from Olive Leaves , 2014 .

[19]  M. Kazemipour,et al.  Development of a simple green extraction procedure and HPLC method for determination of oleuropein in olive leaf extract applied to a multi-source comparative study , 2011 .

[20]  A. Ranalli,et al.  Factors affecting the contents of iridoid oleuropein in olive leaves (Olea europaea L.). , 2006, Journal of agricultural and food chemistry.

[21]  A. Ortuño,et al.  Antioxidant activity of phenolics extracted from Olea europaea L. leaves , 2000 .