Use of advanced techniques for the extraction of phenolic compounds from Tunisian olive leaves: Phenolic composition and cytotoxicity against human breast cancer cells

Abstract

Segura-Carretero et al. ; A comparison among different advanced extraction techniques such as microwave-assisted extraction (MAE), supercritical fluid extraction (SFE) and pressurized liquid extraction (PLE), together with traditional solid-liquid extraction, was performed to test their efficiency towards the extraction of phenolic compounds from leaves of six Tunisian olive varieties. Extractions were carried out at the best selected conditions for each technique; the obtained extracts were chemically characterized using high-performance liquid chromatography (HPLC) coupled to electrospray time-of-flight mass spectrometry (ESI-TOF-MS) and electrospray ion trap tandem mass spectrometry (ESI-IT-MS 2). As expected, higher extraction yields were obtained for PLE while phenolic profiles were mainly influenced by the solvent used as optimum in the different extraction methods. A larger number of phenolic compounds, mostly of a polar character, were found in the extracts obtained by using MAE. Best extraction yields do not correlate with highest cytotoxic activity against breast cancer cells, indicating that cytotoxicity is highly dependent on the presence of certain compounds in the extracts, although not exclusively on a single compound. Therefore, a multifactorial behavior is proposed for the anticancer activity of olive leaf compounds. © 2012 Elsevier Ltd. ; The authors are grateful to the Tunisian Ministry of Higher Education and Scientific Research, to the Spanish Ministry of Education and Science for the project AGL2011-29857-C03-02 and to Andalusian Regional Government Council of Innovation and Science for the excellence projects P09-CTS-4564, P10-FQM-6563, and P11-CTS-7625, and to the University of Granada for the GREIB project GREIB.PYR-2011-02. M.H. and E.B.C. thank the Spanish Science and Innovation Ministry (MICINN) for their "Ramón y Cajal" and "Torres Quevedo" (PTQ-08-03-08076) research contracts. ; Peer Reviewed