Research Group

Dr. Theodore G. Sotiroudis, Research Director (Head)
Dr. V. Papadimitriou, Post Doc

PhD Students
E.Tzika, PhD Student

Msc. Students
Mrs Maria Vamvaka, Chemist
Mrs Vassiliki Tsapra, Biologist
Mrs Vissaria Bartzoka, Chemist

Technicians
Mrs. Maria Roubi
Mr. Stathis Kaldanis

Research objectives

The Enzymology Programme focuses on the study of enzyme structure-function relationships and the development of new diagnostic methods.

Recent emphasis of our activities is given on oxidative enzymes (lipoxygenases, polyphenol oxidases/ tyrosinases, peroxidases) and antioxidant actions, in animal, plant and food extracts (especially olives and olive oil as well as the microalga spirulina (Arthrospira)), in order to understand the effect of these critical oxidation processes on the quality and function of various food products in relation to human health.

In parallel, the formation of specific free radicals, during enzyme and chemical oxidations, in cellular systems and food products is also presently studied. In this respect, plant and food molecular components are extracted and examined for their antioxidant and free radical scavenging activity as well as for their enzyme inhibitory action.

Current used experimental methodology includes methods of measuring enzyme activities, extraction of enzymes from microbial, plant, animal and food systems; methods of enzyme purification and characterization and regulation of enzyme activities by activators, inhibitors, and by covalent modification; methods for measurement of antioxidant activity and spin-trapping Electron Paramagnetic Resonance (EPR) spectroscopy for free radical analysis.

Recent Research Activities of the Enzymology Research Programme

The activities of the Enzymology Research Programme during the last ten years have focused on three research targets.
(a) The development of new enzyme-based diagnostics,
(b) understanding the action of oxidative processes on the quality of virgin olive oil and other plant foods of Mediterranean Diet and developing methodologies for the estimation of the oxidative status in food products
(c) the development of new methodologies for the culture of microalgae (especially Spirulina), aiming on the production of new functional foods and new high added value products.

(a) We have developed a homogeneous enzyme immunoassay for measurement of thyroxine (T3/T4) in serum based on a thyroxine derivative conjugated to glycogen phosphorylase b in collaboration with the private sector (MEDICON S.A.). Conjugation caused inhibition of enzyme activity and the enzyme conjugate was re-activated upon binding of a polyclonal anti-T4 or anti-T3 antibody. Our results permit the development of a clinically useful assay for serum T4 and T3 and other similar serum analytes. The methodology has been patented in Greece (OBI 10041119).

(b) We have developed a new EPR-spin trapping technique for the estimation of the oxidative status in virgin olive oils in collaboration with the oleaginous company ELAIS SA (Greece). We have identified for the first time the presence of proteins and enzyme oxidative activities in virgin olive oil. In this respect, we are studying the action of chemical and enzyme oxidative activities on the stability of olive oil emulsions in presence and absence of natural antioxidants. Recently we have started a research project for the development of an immunoassay for the detection of hazelnut oil adulteration of olive oils. Our paper ''The role of endogenous amphiphiles on the stability of virgin olive oil-in-water emulsions'' by T.G. Sotiroudis, G.T. Sotiroudis, N. Varkas and A. Xenakis published in J.Am.Chem.Soc. (2005) 82, 415-420, has received the 2005 Archer Daniels Midland Award Protein and Co-Products Division for BEST PAPER in Chemistry and Nutrition of the American Oil Chemists’ Society.

(c ) In collaboration with the greek company ALGAE A.C. (Nigrita, Serres) we are studying a cost reduction application of geothermal fluids and sea water for commercial production of the microalga cyanobacterium Spirulina sp. (Arthrospira) in production ponds and photobioreactors. We found that extracts of Spirulina powder produced by ALGAE A.C., contain sulphated polysaccharides and polyphenols, which express strong antioxidant/free radical scavenging activities. Thus this microalgae food product offers valuable nutritional antioxidant components with potential benefits in human health. These microalga components together with the strong Spirulina antioxidant protein phycocyanin can be used as high added value products for the production of new functional foods, feed products and cosmetics.

Microscopic view of cultured Spirulina sp.	Flat plate photobioreactor (70 lt)

List of funded research projects (2000-2006)

1. Program ΕΠΕΤ ΙΙ, ΚΑ-81. Data Bases, National Information System (1998-2000) ''Enzymes in Clinical Diagnosis and Therapy'' (Coordinator NHRF, T.Sotiroudis). Budget 26.000.000 Grd. Collaboration with research group of Laboratory of Biological Chemistry, Medical School of Athens and the National Drug Organization.

2. Research Project O.KA.NA (Organization Against Drugs): ''Investigation of the effect of ibogaine on cAMP- dependent protein kinase of nucleus accubens in morphine-dependent rats'' (1999-2000) Budget: 1.983.000 Grd (Coordinator NHRF, T.Sotiroudis)

3. Program ΕΠΕΤ ΙΙ - ΠΕΝΕΔ 99ΕΔ33 (1999-2001) ''Polyphenols and their polymers (tannins) in virgin olive oil and olive oil waste waters. Antioxidant action and free radical mechanism. The biotechnological importance for health, food and environment'' Budget: 50.000.000 Grd (Coordinator NHRF, T.Sotiroudis). Collaboration with research groups of (a) Charokopio University, Athens, (b) National Agricultural Research Foundation, Subtropics and Olive Institute of Chania, Greece

4. Program ΕΠΕΤ ΙΙ - Subprogram 2, Action 2.1, ΠΑΒΕ-99ΒΕ5(1999-2001) ''Virgin olive oil: Characterization of the effect of pigments and tocopherols on the oxidative stability and development of a method for the estimation of the oxidative condition'', Contract with: ELAIS SA. Budget: 62.105.000 Grd (NHRF 8.200.000 Grd.).

5. Program ΕΠΕΤ ΙΙ - Subprogram 1, Action 2.3, Nutrition Program 97ΔΙΑΤΡΟ-29 (1999-2001) ''Study of the presence and bioavailability of phenolic antioxidants in foods of the Mediterranean diet'' Contract with: Univ. of Thessaloniki Budget: 95.000.000 Grd (NHRF 17.450.000 Grd.)
Collaboration with the research groups of: (a)ELAIS SA. Oleaginous Company (b) Prof.Α.Kaffatos, Clinic of preventive medicine & nutrition, Medical School, Univ.of Crete (c) Prof. D. Boskou, Food Chem. & Technol. Lab., Univ. of Thessaloniki (d) Prof. Ι.Gerothanassis, Org.Chem & Biochem. Lab., Chemistry dept., Univ.of Ioannina

6. Program ''ΣΥΝΕΡΓΑΣΙΑ'' of the Dir.1334/02 - ELAIOURGIKI - ΟΠΕΚΕΠΕ (2003-4) ''Determination of the most significant and usual quality problems encountered in greek olive oils. Evaluation and therapeutic actions'' Budget 23.600,00 €
Collaboration with the research groups of: (a)ELAIOURGIKI SA., (b) Assos.Prof.M.Tsimidou, Food Chem. & Technol. Lab., Univ. of Thessaloniki (c) As.Prof.Ε.Psomiadou, Food Chem lab., Chemistry dept., Univ.of Ioannina

7. Program 01 PRAXE 11 (Hellenic General Secretariat of Research & Technology) ''Production of Microalgae and High Additive Value Products'' (2003-2004). (Coordinator NHRF T.Sotiroudis ) Budget: 44.000,00 € . Collaboration with the research group of Prof. E.Nerantzis, TEI, Athens

8. Joint Research and Technology Programme Greece-Spain, ΕΠΑν.Μ.4.3(006-γ) (Hellenic General Secretariat of Research & Technology) ''Antioxidant and Biomodulation Activities of Spirulina sp. (Arthrospira sp.) Bioactive Components'' (2004-2006). (Coordinator NHRF T.Sotiroudis ) Budget:11.740,00€ . Collaboration with the research group of Prof. C.Jimenez-Gamez, Department of Ecology, University of Malaga, Spain and the research groups of Prof. L. Skaltsounis and As.Prof. I. Chinou, University of Athens and Prof. E.Nerantzis, TEI,Athens.

9. Program''Cretan Collaboration'' of the Dir.1334/02 - ΟΠΕΚΕΠΕ - Agr.Unions of Siteia, Peza, Mylopotmos, Mirambello (2004-5) ''Study of the parameters related to the quality of virgin olive oil; effect of the maturity degree on the natural antioxidant content.'' Budget 29.759,52 €
Collaboration with the research group of Prof. Ν.Haniotakis, Chemistry Dept., Univ.of Crete

11. "Environmental Cancer, Nutrition and Individual Susceptibility" (ECNIS, EU FP6 Network of Excellence, 2005-2009; co-ordinator: Dr. K. Rydzynski, NOFER Institute, Lodz, Poland; Greek participating partner¨Dr. S. Kyrtopoulos (http://www.eie.gr/nhrf/institutes/ibrb/index-en.html). NHRF budget for first 18 months, 50% EC contribution: 216.640 €)

12. Program ΠΑΒΕΤ 2005: ''Production of high added value products by application of lipases as biocatalysts'' Coordinator: ΝΕΟΚΕΜ S.A. Budget: 35.000,00€.

13. Joint Research and Technology Programme ΕΠΑΝ Greece-France 2006-7. ''Biocatalysis of immobilized enzymes in mesoporous materials for the biotechnological production of high added value products'' Budget: 12.400,00€. Coordinator NHRF: Dr. A.Xenakis.

Selected Recent Publications

1. Georgalaki, M.D., Sotiroudis, T.G. and Xenakis, A. (1998)
The presence of oxidizing enzyme activities in virgin olive oil. J. Amer. Oil. Chem. Soc, 75, 155-159.

2. Georgalaki, M.D., Bachmann, A., Sotiroudis, T.G, Xenakis, A., Porzel, A. and Feussner, I. (1998)
Characterization of a 13-lipoxygenase from virgin olive oil and oil bodies of olive endosperms. Fett/Lipid, 100, 554-560.

3. Psarra, A.-M.G, Pfeiffer, B., Giannakopoulou, M., Sotiroudis, T.G., Stylianopoulou, F., and Hamprecht, B. (1998)
Immunocytochemical localization of glycogen phosphorylase kinase in rat brain sections and in glial and neuronal primary cultures. J. Neurocytol. 27, 779-790.

4. Karapitta, D.D., Xenakis, A., Papadimitriou, A. and Sotiroudis,T.G. (2001)
A new homogeneous enzyme immunoassay for thyroxine using glycogen phosphorylase b- thyroxine conjugates, Clin. Chim. Acta , 308, 99-106.

5. Karapitta, D.D, Sotiroudis,T.G, Papadimitriou,.A and, Xenakis, A. (2001)
A homogeneous enzyme immunoassay for triiodothyronine in serum, Clin. Chem. 47, 569-57.

6. Skoutas D., Haralabopoulos, D., Avramiotis, S., Sotiroudis, T.G. and Xenakis, A. (2001)
Virgin olive oil: Free radical production studied with spin trapping EPR spectroscopy J. Amer. Oil. Chem. Soc. 78, 1121-1125.

7. Sotiroudis, T.G., Kyrtopoulos, S.A. Xenakis, A. and Sotiroudis, G.T. (2003)
Potential cancer chemopreventive activities of minor components of olive oil. Ital.J.Food.Sci. 15, 169-185.

8. Tzika, E., Papadimitriou, V. Sotiroudis, T.G. and Xenakis, A. (2004) ''Chemical and enzymatic oxidation of oleuropein: an EPR study'' Chem.Phys.Lipids. 130, 61.

9. Mastorakis, M., Sotiroudis, T.G, Xenakis, A. and Miniadis-Meimaroglou, S. (2004)
''Spectrophotometric analysis of enzymic and non-enzymic oxidation of oleuropein'' Chem.Phys.Lipids. 130, 58.

10. Papadimitriou, V., Maridakis, G.A., Sotiroudis, T.G., Xenakis, A. (2005) Antioxidant activity of polar extracts from olive oil and olive mill wastewaters: an EPR and photometric study. Eur.J.Lipid Sci.Technol. 107, 513-520.

11. Papadimitriou, V., Sotiroudis, T.G., and Xenakis, A. (2005) Olive oil microemulsions as a biomimetic medium for enzymatic studies:oxidation of oleuropein. J.Amer.Oil Chem.Soc. 82, 335-340.

12. Sotiroudis, T.G., Sotiroudis, G.T., Varkas, N. and Xenakis, A. (2005) The role of endogenous amphiphiles on the stability of virgin olive oil-in-water emulsions. J.Amer.Oil Chem.Soc. 82, 415-420.

13. Arvanitis, A., Sotiroudis, T.G, Nerantzis, E., Fournadzhieva, S. and Koultsiakis, E. (2004) ''Mass culture of the microalga Spirulina using geothermal fluids in Greece. Antioxidant activities of Spirulina powder extracts.'' Proceedings of the International Conference "Geothermal Energy Applications in Agriculture" Athens, 3-4/5/2004,

14. Sotiroudis, T.G., Nerantzis, E.T.,. Deliyannis, C and Karydakis, G. (2005) Industrial large-scale culture of Spirulinasp. for the production of microalgae biomass and high additive value products in greek arid seacoasts A research project. Proceedings of the International Symposium ''Cyanobacteria for Health, Science and Development'' Embiez Island, France, 3-6 May 2004 in ''Memoires de l'Institut Oceanographique Paul Ricard'' pp.82-83.

15. Papadimitriou, V., Sotiroudis, T.G., Xenakis, A., Sofikiti, N., Stavyiannoudaki, V. and Chaniotakis, N.A. (2006) Oxidative stability and radical scavenging activity of extra virgin olive oils by using Electron Paramagnetic Resonance spectroscopy,Anal.Chim.Acta, 573-574, 453-458.

16. Sotiroudis, T.G. (2006) Potential health effects of Spirulina, BIO 19, 66-69.

17. Papadimitriou, V., Sotiroudis, T.G., Xenakis, A. (2007) Olive oil microemulsions: enzymatic activities and structural characteristics, Langmuir, 23, 2071-2077.

18. Sotiroudis, T.G. and Kyrtopoulos, S.A. (2007) Anticarcinogenic compounds of olive oil and related biomarkers. In : "Dietary vitamins, polyphenols, selenium and probiotics: biomarkers of exposure and mechanisms of anticarcinogenic action" pp.134-139. Akesson, B.& Mercke,P. eds. WP9 ECNIS Report, ECNIS, Lodz, Poland.

19. Tzika, E.D., Papadimitriou, V., Sotiroudis, T.G. and Xenakis, A. Oxidation of oleuropein: Electron Paramagnetic Resonance and spectrophotometric studies (submitted).

20. Tzika, E.D., Papadimitriou, V., Sotiroudis, T.G. and Xenakis, A. Antioxidant properties of fruits and vegetables shots and juices: An Electron paramagnetic Resonance stydy, (submitted).

21. Tzika, E.D., Sotiroudis, T.G., Papadimitriou, V. and Xenakis, A. Partial characterization of peroxidase activity in olive fruits (Koroneiki variety), (submitted).