isolation, identification and evaluation of natural antioxidants

165 Pages·2012·4.82 MB·English

ISOLATION, IDENTIFICATION AND
EVALUATION OF NATURAL
ANTIOXIDANTS FROM AROMATIC
HERBS CULTIVATED IN LITHUANIA
CENTRALE LANDBOUWCATALOGUS
0000 0889 7700
Promotor
Prof. Dr. Ae. de Groot, hoogleraar in de bio-organische chemie, Wageningen
Universiteit
Co-promotoren
Dr. T.A. van Beek, universitair hoofddocent, Laboratorium voor Organische
Chemie, Wageningen Universiteit
Dr. Ir. J.P.H. Linssen, universitair hoofddocent, Sectie Levensmiddelenleer,
Wageningen Universiteit
Promotiecommissie
Prof. Dr. Ir. I.M.C.M. Rietjens (Wageningen Universiteit)
Prof. Dr. Ir. P.R. Venskutonis (Kaunas University of Technology, Lithuania)
Prof. Dr. Ir. A.G.J. Voragen (Wageningen Universiteit)
Dr. H.A.G. Niederlander (Rijksuniversiteit Groningen)
j^30l
/Jf
Airidas Dapkevicius
ISOLATION, IDENTIFICATION AND
EVALUATION OF NATURAL
ANTIOXIDANTS FROM AROMATIC
HERBS CULTIVATED IN LITHUANIA
(with a summary in English)
(met een samenvatting in het Nederlands)
(su santrauka lietuviskai)
(com resumo em Portugues)
Proefschrift
ter verkrijging van de graad van doctor
op gezag van de rector magnificus
van Wageningen Universiteit,
prof. dr. ir. L. Speelman
in het openbaar te verdedigen
op dinsdag 29 januari 2002
des namiddags te twee uur in de Aula
(, 3 Qq I 6
ISBN 90-5808-578-3
To my children leva and Simonas
General introduction
1.1 Lipid oxidation in general 1
1.2 Food lipid oxidation mechanisms 2
1.2.1 Free radical autoxidation 2
1.2.2 Photooxidation 5
1.2.3 Enzyme-initiated lipid oxidation 6
1.2.4 Metal-catalysed lipid oxidation 6
1.2.5 Formation of secondary products of lipid oxidation 7
1.3 Prevention of lipid oxidation by antioxidants 12
1.3.1 Primary and secondary antioxidants 13
1.3.2 Synthetic and natural antioxidants 17
1.3.3 Inhibitors of enzyme-initiated lipid oxidation 18
1.3.4 Antioxidative enzymes 18
1.3.5 Molecular structure and antioxidative efficiency 19
1.4 Methods of antioxidant activity assessment 20
1.4.1 Measuring lipid oxidation 20
1.4.1.1 Evaluation of primary oxidation changes 21
1.4.1.2 Assessment of secondary oxidation changes 21
1.4.2 Stability tests and model systems for antioxidant
activity evaluation 22
1.5 Natural antioxidants 26
1.5.1 Tocopherols 27
1.5.2 Ascorbic acid 28
1.5.3 Other antioxidant substances and their sources 28
1.6 Application of natural antioxidants 32
1.7 Scope and content of this thesis 33
1.8 References and notes 35
Antioxidant activity of extracts obtained by different isolation
procedures from some aromatic herbs grown in Lithuania
2.1 Introduction 49
2.2 Experimental 50
2.2.1 Plant material 50
2.2.2 Isolation techniques 51
2.2.3 Evaluation of antioxidant activity 53
2.2.3.1 /3-Carotene bleaching (agar diffusion method) 53
2.2.3.2 j3-Carotene bleaching (spectrophotometric
method) 54
2.3 Results and discussion 55
2.3.1 Yield of isolates 55
2.3.2 Results of the agar diffusion test 56
2.3.3 Results of the spectrophotometric test 59
2.4 Conclusions 61
2.5 References 61
Rapid spectroscopic screening for antioxidant activity in herb
isolates with the /3-carotene-linoleic acid model system
3.1 Introduction 65
3.2 Experimental 69
3.2.1 Preparation of herb isolates 69
3.2.2 Spectrophotometric evaluation of j8-carotene
bleaching in the /3-CLAMS 69
3.3 Results and discussion 70
3.4 Conclusions 72
3.5 References 73
On-line detection of antioxidative activity in HPLC eluates by
chemiluminescence
4.1 Introduction 75
4.2 Experimental 77
4.2.1 HPLC-CL conditions and instrumental setup 77
4.2.2 HPLC-CL reagents and tested antioxidants 78
4.3 Results and discussion 79
4.3.1 Initial tests 79
4.3.2 Off-line CL experiments 80
4.3.3 Optimisation of the HPLC-CL system 83
4.3.4 Detection of radical scavenging activity 84
4.4 Conclusions 87
4.5 References 88
Evaluation and comparison of two improved techniques for the on
line detection of antioxidants in HPLC eluates
5.1 Introduction 91
5.2 Experimental 92
5.2.1 HPLC-CL instrumental set-up 92
5.2.2 HPLC-CL reagents and gradient conditions 92
5.2.3 HPLC-DPPH* instrumental set-up 94
5.2.4 HPLC-DPPH* reagents and gradient conditions 94
5.2.5 Sample preparation 95
5.2.6 Detection limits, minimum detectable amounts
(MDA), and minimum detectable concentrations
(MDC) 95
5.2.7 Statistical analysis 97
5.3 Results and discussion 97
5.3.1 Improvements in DPPH* and luminol CL detection 97
5.3.2 The luminol chemiluminescence quenching method 98
5.3.3 The DPPH* quenching method 99
5.3.4 Consequences of eluent composition and eluent and
reagent solution pH for MDA values with DPPH*
detection 101
5.3.5 Comparison of MDC and MDA values for both
methods 103
5.4 Conclusions 104
5.5 References 105
Isolation and structure elucidation of radical scavengers from
Thymus vulgaris leaves
6.1 Introduction 107
6.2 Experimental 107
6.2.1 General experimental procedures 107
6.2.2 Plant material 109
6.2.3 Extraction and isolation procedures 109
6.2.3.1 Procedure I 109
6.2.3.2 ProcedureII 111
6.2.4 Assessment of radical scavenging activity of fractions 111
6.2.5 Off-line ABTS*+ radical scavenging assay 112
6.2.6 Off-line DPPH* radical scavenging assay 112
6.3 Results and discussion 113
6.3.1 Activity-guided isolation of radical scavenging
compounds 113
6.3.2 Structure elucidation 115
6.3.3 Radical scavenging activity detected with
HPLC-DPPH* 119
6.3.4 DPPH* and ABTS*+ scavenging efficiency of
compounds 1 and 2 120
6.4 Conclusions 121
6.5 References 122
General discussion 125
Summary 131
Samenwatting 135
Trumpas disertacijos turinys 139
Resumo 143
Acknowledgements 147
Curriculum vitae 149
List of publications 151
A^OJW, 3^
Due to its specific aroma and the volatility of thymol and carvacrol, the essential
oil from thyme has a limited use as a food antioxidant.
This thesis.
Due to the complexity of food products and the variety of possible oxidation
mechanisms, it is not possible to find a single antioxidant that can control all
factors involved in food oxidation.
This thesis.
Six, P. 1994. Current research in natural food antioxidants. Inform, 5, 679—687.
Decker, E.A. 1998. Strategies for manipulating the prooxidative/antioxidative
balance of foods to maximize oxidative stability. Trends Food Sci. Technol., 9,
241-248.
It is perfectly possible for an antioxidant to protect lipids against oxidative damage
whilst accelerating damage to other biomolecules.
Aruoma, O.I., Spencer, J.P.E., Warren, D., Jenner, P., Butler, J. and Halliwell, B.
1997. Characterization of food antioxidants, illustrated using commercial garlic
and ginger preparations. Food Chem., 60, 149-156.
"Natural * safe".
Reische, D.W., Lillard, D.A. and Eitenmiller, R.R. 1998. Antioxidants, p. 423-448.
In: C.C. Akoh andD.B. Min (eds). Food Lipids. Marcel Dekker, New York.
Pokorny, J. 1991. Natural antioxidants for food use. Trends Food Sci. Technol., 2,
223-227.
When reporting analytical results on commercial phytopharmaceuticals or dietary
supplements, researchers should always report brand names, type, dosage and
batch numbers so that others may repeat their investigations.
Petty, H.R., Fernando, M., Kindzelskii, A.L., Zarewych, B.N., Ksebati, M.B.,
Hryhorczuk, L.M. and Mobashery, S. 2001. Identification of colchicine in
placental blood from patients using herbal medicines. Chem. Res. Toxicol., 14,
1254-1258.
Economical considerations are just one - and not always the most important -
reason for the brain-drain from Eastern European countries.
Life is a constant battle to avoid becoming rancid.
Gary G. Duthie
Stellingen behorend bij het proefschrift: Isolation, Identification and Evaluation of Natural
Antioxidants from Aromatic Herbs Cultivated in Lithuania
Airidas Dapkevicius, 29 januari 2002