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Influence of olive leaf processing on the bioaccessibility of bioactive polyphenols Margarita H. Ahmad-Qasem, Jaime Canovas, Enrique BarrajonCatalan, Jose E. Carreres, Vicente Micol, and Jose V. Garcia Perez J. Agric. Food Chem., Just Accepted Manuscript • Publication Date (Web): 13 Jun 2014 Downloaded from http://pubs.acs.org on June 15, 2014
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Journal of Agricultural and Food Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
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Journal of Agricultural and Food Chemistry
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Influence of olive leaf processing on the bioaccessibility of bioactive
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polyphenols
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Margarita H. Ahmad-Qasem a, Jaime Cánovas, Enrique Barrajón-Catalán b,
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José E. Carreres c, Vicente Micol b and José V. García-Pérez a,*
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a
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Departamento de Tecnología de Alimentos. Universitat Politècnica de València.
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Valencia 46022, Spain.
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b
Grupo de Análisis y Simulación de Procesos Agroalimentarios (ASPA).
Instituto de Biología Molecular y Celular. Universidad Miguel Hernández.
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Elche 03202, Spain.
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c
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Paterna 46980, Spain.
AINIA Centro tecnológico. Parque tecnológico de Valencia. Benjamin Franklin.
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* Corresponding author. Tel.: +34 96 3879376; Fax: +34 96 3879839 E-mail address:
[email protected] (José V. García-Pérez) 1
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ABSTRACT
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Olive leaves are rich in bioactive compounds which are beneficial for
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humans. The objective of this work was to assess the influence of the
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processing conditions (drying and extraction) of olive leaves on the extract’s
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bioaccessibility. Thus, extracts obtained from dried olive leaves (hot air drying at
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70 and 120 °C or freeze drying) by means of conventional or ultrasound
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assisted extraction were subjected to in vitro digestion. Antioxidant capacity,
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total phenolic content and HPLC-DAD/MS-MS analysis were carried out during
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digestion.
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The dehydration treatment used for the olive leaves did not have a
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meaningful influence on bioaccessibility. The digestion process significantly
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(p0.9999).
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Quantitative evaluation of oleuropein, verbascoside luteolin glucoside was
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performed by means of a six-point regression curve (r2>0.996, 0.997 and 0.986, 11
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respectively) in a concentration range between 0.25 µg/mL and 10 mg/mL,
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using oleuropein, verbascoside and luteolin glucoside as reference external
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standard and evaluated by DAD signal. LOD (Limit of Detection) was 0.10
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µg/mL and Limit of Quantification (LOQ) was 0.25 µg/mL.
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Statistical analysis
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Analysis of variance (ANOVA) was applied in order to determine the
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significant effects of in vitro digestion on extract composition taking a
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significance level of 95 %. The statistical analysis was performed using
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Statgraphics-Plus software 5.1 (Statistical Graphics, Rockville, MD, USA).
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RESULTS AND DISCUSSION
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Initial characterization of olive leaf extracts
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Previous studies have reported that the composition of olive leaf extracts
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is greatly influenced by processing conditions, namely the drying and extraction.
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In such a way, a conventional extraction method 10 was used with leaves hot air
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dried at 70 (HAD-70) and 120 °C (HAD-120) and freeze dried (FD). Moreover,
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HAD-120 leaves were subjected to ultrasound assisted extraction (HAD-
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120+US) 20.
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As can be observed in Table 1, the TPC and AC of the extracts used
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were significantly (p
