The aim of the present study was to improve the recovery of polyphenols from olive leaves (OL) by optimizing a multistage extraction scheme; provided that the olive leaves have been previously steam blanched. The maximum total phenol content expressed in ppm caffeic acid equivalents was obtained at pH 2, particle size 0.315 mm, solid-liquid ratio 1:7 and aqueous ethanol concentration 70% (v/v). The optimum duration time of each extraction stage and the operation temperature, were chosen based on qualitative and quantitative analysis of oleuropein (OLE), verbascoside, luteolin-7- O-glucoside and apigenin-7- O-glucoside performed by high performance liquid chromatography with diode array detector (HPLC-DAD). The optimum conditions for multistage extraction were 30 min total extraction time (10 min × 3 stages) at 85 °C. The 80% of the total yield of polyphenols was obtained at the 1st stage of the extraction. The total extraction yield of oleuropein was found 23 times higher (103.1 mg OLE/g dry weight (d.w.) OL) compared to the yield (4.6 mg OLE/g d.w. OL) obtained by the conventional extraction method (40 °C, 48 h). However, from an energetic and hence from an economical point of view it is preferable to work at 40 °C, since the total extraction yield of polyphenolic compounds was only 17% higher for a double increase in the operating temperature ( i.e., 85 °C).
References
[1]
Schieber, A.; Stintzing, F.C.; Carle, R. By-products of plant food processing as a source of functional compounds-recent developments. Trends Food Sci. Technol. 2001, 12, 401–413, doi:10.1016/S0924-2244(02)00012-2.
Shi, J.; Nawaz, H.; Pohorly, J.; Mittal, G.; Kakuda, Y.; Jiang, Y. Extraction of polyphenolics from plant material for functional foods—Engineering and technology. Food Rev. Int. 2005, 21, 139–166, doi:10.1081/FRI-200040606.
[4]
Japón-Luján, R.; Luque de Castro, M.D. Superheated liquid extraction of oleuropein and related biophenols from olive leaves. J. Chromatogr. A 2006, 1136, 185–191.
[5]
Servili, M.; Montedoro, G.F. Contribution of phenolic compounds to virgin olive oil quality. Eur. J. Lipid Sci. Technol. 2002, 104, 602–613, doi:10.1002/1438-9312(200210)104:9/10<602::AID-EJLT602>3.0.CO;2-X.
[6]
Kim, T.J.; Kim, J.H.; Jin, Y.R.; Yun, Y.P. The inhibitory effect and mechanism of luteolin 7-glucoside on rat aortic vascular smooth muscle cell proliferation. Arch. Pharm. Res. 2006, 29, 67–72, doi:10.1007/BF02977471.
[7]
Omar, S.H. Cardioprotective and neuroprotective roles of oleuropein in olive. Saudi Pharm. J. 2010, 18, 111–121, doi:10.1016/j.jsps.2010.05.005.
[8]
Benavente-Garcia, O.; Castillo, J.; Lorente, J.; Ortuno, A.; del Rio, J.A. Antioxidant activity of phenolics extracted from Olea europaea L. leaves. Food Chem. 2000, 68, 457–462, doi:10.1016/S0308-8146(99)00221-6.
[9]
Bendjeddou, D.; Lalaoui, K.; Satta, D. Immunostimulating activity of the hot water-soluble polysaccharide extracts of Anacyclus pyrethrum, Alpinia galanga and Citrullus colocynthis. J. Ethnopharmacol. 2003, 88, 155–160, doi:10.1016/S0378-8741(03)00226-5.
[10]
Dong, C.H.; Xie, X.Q.; Wang, X.L.; Zhan, Y.; Yao, Y.J. Application of Box-Behnken design in optimization for polysaccharides extraction from cultured mycelium of Cordyceps sinensis. Food Bioprod. Process. 2009, 87, 139–144, doi:10.1016/j.fbp.2008.06.004.
[11]
Lee, W.C.; Yusof, S.; Hamid, N.S.A.; Baharin, B.S. Optimizing conditions for hot water extraction of banana juice using response surface methodology (RSM). J. Food Eng. 2006, 75, 473–479, doi:10.1016/j.jfoodeng.2005.04.062.
[12]
Corsano, G.; Montagna, J.M.; Aguirre, P.A. Design and planning optimization of multiplant complexes in the food industry. Food Bioprod. Process. 2007, 85, 381–388, doi:10.1205/fbp07072.
[13]
Savournin, C.; Elias, B.R.; Dargouth-Kesraoui, F.; Boukef, K.; Balansard, G. Rapid high-performance liquid chromatography analysis for the quantitative determination of oleuropein in Olea europaea leaves. J. Agric. Food Chem. 2001, 49, 618–621, doi:10.1021/jf000596+.
[14]
Japón-Luján, R.; Luque-Rodríguez, J.M.; Luque de Castro, M.D. Dynamic ultrasound-assisted extraction of oleuropein and related biophenols from olive leaves. J. Chromatogr. A 2006, 1108, 76–82.
[15]
Japón-Luján, R.; Luque-Rodríguez, J.M.; Luque de Castro, M.D. Multivariate optimisation of the microwave-assisted extraction of oleuropein and related biophenols from olive leaves. Anal. Bioanal. Chem. 2006, 385, 753–759, doi:10.1007/s00216-006-0419-0.
[16]
Tabera, J.; Guinda, A.; Ruiz Rodríguez, A.; Se？oráns, F.J.; Ibá？ez, E.; Albi, T. Counter-current supercritical fluid extraction and fractionation of high-added-value compounds from a hexane extract of olive leaves. J. Agric. Food Chem. 2004, 52, 4774–4779, doi:10.1021/jf049881+.
[17]
Tsochatzidis, N.A.; Guiraud, P.; Wilhelm, A.M.; Delmas, H. Determination of velocity, size and concentration of ultrasonic cavitation bubbles by the phase-Doppler technique. Chem. Eng. Sci. 2001, 56, 1831–1840, doi:10.1016/S0009-2509(00)00460-7.
[18]
Peki？, B.; Kova？, V.; Alonso, E.; Revilla, E. Study of the extraction of proanthocyanidins from grape seeds. Food Chem. 1998, 61, 201–206, doi:10.1016/S0308-8146(97)00128-3.
[19]
Mylonaki, S.; Kiassos, E.; Makris, D.P.; Kefalas, P. Optimisation of the extraction of olive (Olea europaea) leaf phenolics using water/ethanol-based solvent systems and response surface methodology. Anal. Bioanal. Chem. 2008, 392, 977–985, doi:10.1007/s00216-008-2353-9.
[20]
Spigno, G.; Tramelli, L.; de Faveri, D.M. Effects of extraction time, temperature and solvent on concentration and antioxidant activity of grape marc phenolics. J. Food Eng. 2007, 81, 200–208, doi:10.1016/j.jfoodeng.2006.10.021.
[21]
Williamson, G. Polyphenols Extraction from Foods. In Methods in Polyphenol Analysis, 1st ed.; Escribano-Balón, M.T., Santos-Buelga, C., Eds.; Royal Society of Chemistry: Cambridge, UK, 2003.
[22]
Stamatopoulos, K.; Katsoyannos, E.; Chatzilazarou, A.; Konteles, S.J. Improvement of oleuropein extractability by optimising steam blanching process as pre-treatment of olive leaf extraction via response surface methodology. Food Chem. 2012, 133, 344–351, doi:10.1016/j.foodchem.2012.01.038.
[23]
Braca, A.; de Tommasi, N.; di Bari, L.; Pizza, C.; Politi, M.; Morelli, I. Antioxidant principles from Bauhinia tarapotensis. J. Nat. Prod. 2001, 64, 892–895, doi:10.1021/np0100845.
[24]
Chun, O.K.; Kim, D.O.; Smith, N.; Schroeder, D.; Han, J.T.; Lee, C.Y. Daily consumption of phenolics and total antioxidant capacity from fruit and vegetables in the American diet. J. Sci. Food Agric. 2005, 85, 1715–1724, doi:10.1002/jsfa.2176.
[25]
Meireles, M.A.A. Extracting Bioactive Compounds for Food Products Theory and Applications; CRC Press: Boca Raton, FL, USA, 2009.
[26]
Gikas, E.; Papadopoulos, N.; Tsarbopoulos, A. Kinetic study of the acid hydrolysis of oleuropein, the major bioactive metabolite of olive oil. J. Liquid Chromatogr. Relat. Technol. 2006, 29, 497–508, doi:10.1080/10826070500474113.
[27]
Bilek, S.E. The effects of time, temperature, solvent:solid ratio and solvent composition on extraction of total phenolic compound from dried olive (Olea europaea L.) leaves. GIDA J. Food 2010, 35, 411–416.
[28]
Naczk, M.; Shahidi, F. Phenolics in cereals, fruits and vegetables: Occurrence, extraction and analysis. J. Pharm. Biomed. Anal. 2006, 41, 1523–1542, doi:10.1016/j.jpba.2006.04.002.
[29]
Alonso, E.; Bourzeix, M.; Revilla, E. Suitabilitiy of water-ethanol mixtures for the extraction of catechins and proanthocyanidins from Vitis vinifera seeds contained in a winery by-product. Seed Sci. Technol. 1991, 19, 545–552.
[30]
Yilmaz, Y.; Toledo, R.T. Oxygen radical absorbance capacities of grape/wine industry byproducts and effect of solvent type on extraction of grape seed polyphenols. J. Food Compos. Anal. 2006, 19, 41–48, doi:10.1016/j.jfca.2004.10.009.
[31]
Naczk, M.; Shahidi, F. Extraction and analysis of phenolics in food. J. Chromatogr. A 2004, 1054, 95–111.
[32]
Karadag, A.; Ozcelik, B.; Saner, S. Review of methods to determine antioxidant capacities. Food Anal. Methods 2009, 2, 41–60, doi:10.1007/s12161-008-9067-7.
[33]
Huang, D.; Ou, B.; Prior, R.L. The chemistry behind antioxidant capacity assays. J. Agric. Food Chem. 2005, 53, 1841–1856, doi:10.1021/jf030723c.
[34]
Hutzler, P.; Fischbach, R.; Heller, W.; Jungblut, T.P.; Reuber, S.; Schmitz, R. Tissue localization of phenolic compounds in plants by confocal laser scanning microscopy. J. Exp. Bot. 1998, 49, 953–965.
[35]
Bouaziz, M.; Grayer, R.J.; Simmonds, M.S.J.; Damak, M.; Sayadi, S. Identification and antioxidant potential of flavonoids and low molecular weight phenols in olive cultivar chemlali growing in Tunisia. J. Agric. Food Chem. 2005, 53, 236–241, doi:10.1021/jf048859d.
