Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Potato and Mushroom Polyphenol Oxidase Activities Are Differently Modulated by Natural Plant Extracts
Kuijpers, T.F.M. ; Herk, T. van; Vincken, J.P. ; Janssen, R.H. ; Narh, D.L. ; Berkel, W.J.H. van; Gruppen, H. - \ 2014
Journal of Agricultural and Food Chemistry 62 (2014)1. - ISSN 0021-8561 - p. 214 - 221.
tyrosinase inhibitors - chlorogenic acid - ilex-paraguariensis - constituents - activation - licorice - identification - mechanism - agents - sds
Enzymatic browning is a major quality issue in fruit and vegetable processing and can be counteracted by different natural inhibitors. Often, model systems containing a single polyphenol oxidase (PPO) are used to screen for new inhibitors. To investigate the impact of the source of PPO on the outcome of such screening, this study compared the effect of 60 plant extracts on the activity of PPO from mushroom (Agaricus bisporus, AbPPO) and PPO from potato (Solanum tuberosum, StPPO). Some plant extracts had different effects on the two PPOs: an extract that inhibited one PPO could be an activator for the other. As an example of this, the mate (Ilex paraguariensis) extract was investigated in more detail. In the presence of mate extract, oxygen consumption by AbPPO was found to be reduced >5-fold compared to a control reaction, whereas that of StPPO was increased >9-fold. RP-UHPLC-MS analysis showed that the mate extract contained a mixture of phenolic compounds and saponins. Upon incubation of mate extract with StPPO, phenolic compounds disappeared completely and saponins remained. Flash chromatography was used to separate saponins and phenolic compounds. It was found that the phenolic fraction was mainly responsible for inhibition of AbPPO and activation of StPPO. Activation of StPPO was probably caused by activation of latent StPPO by chlorogenic acid quinones.
The anti-browning agent sulfite inactivates Agaricus bisporus tyrosinase through covalent modification of the copper-B site
Kuijpers, T.F.M. ; Gruppen, H. ; Sforza, S. ; Berkel, W.J.H. van; Vincken, J.P. - \ 2013
FEBS Journal 280 (2013)23. - ISSN 1742-464X - p. 6184 - 6195.
glutathione conjugate formation - crystal-structure - mushroom tyrosinase - polyphenol oxidase - chlorogenic acid - plant - inhibition - metabolism - thioether - sequence
Sulfite salts are widely used as antibrowning agents in food processing. Nevertheless, the exact mechanism by which sulfite prevents enzymatic browning has remained unknown. Here, we show that sodium hydrogen sulfite (NaHSO3 ) irreversibly blocks the active site of tyrosinase from the edible mushroom Agaricus bisporus, and that the competitive inhibitors tropolone and kojic acid protect the enzyme from NaHSO3 inactivation. LC-MS analysis of pepsin digests of NaHSO3 -treated tyrosinase revealed two peptides showing a neutral loss corresponding to the mass of SO3 upon MS(2) fragmentation. These peptides were found to be homologous peptides containing two of the three histidine residues that form the copper-B-binding site of mushroom tyrosinase isoform PPO3 and mushroom tyrosinase isoform PPO4, which were both present in the tyrosinase preparation used. Peptides showing this neutral loss behavior were not found in the untreated control. Comparison of the effects of NaHSO3 on apo-tyrosinase and holo-tyrosinase indicated that inactivation is facilitated by the active site copper ions. These data provide compelling evidence that inactivation of mushroom tyrosinase by NaHSO3 occurs through covalent modification of a single amino-acid residue, probably via addition of HSO3 (-) to one of the copper-coordinating histidines in the copper-B site of the enzyme
Diversity of (dihydro) hydroxycinnamic acid conjugates in Colombian potato tubers
Narvaez Cuenca, C.E. ; Vincken, J.P. ; Zheng, Chaoya ; Gruppen, H. - \ 2013
Food Chemistry 139 (2013)1-4. - ISSN 0308-8146 - p. 1087 - 1097.
chlorogenic acid - liquid-chromatography - kukoamine-a - lc-msn - anthocyanins - polyamine - l. - glycoalkaloids - identification - accumulation
In potato tuber, caffeic acid (the predominant hydroxycinnamic acid (HCA)), its conjugates (HCAcs; i.e. chlorogenic acid (ChA), crypto-ChA, and neo-ChA), and anthocyanin-linked HCAs have been extensively described in the literature. In contrast, only little information is available on the occurrence of other HCAcs and didydrohydroxycinnamic acid conjugates (DHCAcs). Fifteen Colombian potato cultivars were screened for these less commonly described conjugates by reversed-phase ultrahigh performance liquid chromatography coupled to a diode array detector and a heated electrospray ionisation mass spectrometer. A total of 62 HCAs/HCAcs/DHCAcs were found in extracts from peel and flesh. Among them, only twelve compounds were common to all cultivars in both peel and flesh. The less commonly described compounds accounted for 7.1–20.1% w/w of the total amount of HCAs/HCAcs/DHCAcs in whole tubers, highlighting their contribution to the total phenolic profile of potato tubers. Among all cultivars, the abundance (mg/100 g DW whole tuber) of neo-ChA (0.8–7.4) ranged in similar quantities as the less commonly reported feruloyl octopamine (1.2–5.2), 5-O-feruloyl quinic acid (0.1–7.5), cis-ChA (1.1–2.2), caffeoyl putrescine (0.6–2.5), sinapoyl hexose (0.1–1.8), N1,N14-bis-(dihydrocaffeoyl) spermine (0.2–1.7), N1,N10-bis-(dihydrocaffeoyl) spermidine (1.1–2.6), and N1,N5,N14-tris-(dihydrocaffeoyl) spermine (trace – 11.1).
Seasonal accumulation of major alkaloids in organs of pharmaceutical crop Narcissus Carlton
Lubbe, A. ; Gude, H. ; Verpoorte, R. ; Choi, C.Y. - \ 2013
Phytochemistry 88 (2013). - ISSN 0031-9422 - p. 43 - 53.
amaryllidaceae alkaloids - chlorogenic acid - metabolomic analysis - cancer-cells - galanthamine - apoptosis - root - nmr
Narcissus pseudonarcissus (L.) cv. Carlton is being cultivated as a main source of galanthamine from the bulbs. After galanthamine, haemanthamine and narciclasine are the next most abundant alkaloids in this cultivar. Both these compounds are promising chemical scaffolds for potential anticancer drugs. For further research and drug development, a reliable supply of these compounds will be needed. In this study a field experiment was conducted to investigate the levels of galanthamine, haemanthamine and narciclasine in plants of N. pseudonarcissus cv. Carlton. In a field experiment alkaloids in the bulbs, leaves and roots were analyzed by quantitative 1H NMR to monitor the variations during the growing season. Major primary and secondary metabolites were identified in the various plant parts. Multivariate data analysis was performed on the 1H NMR spectra to investigate how metabolites changed in the plant organs over time. The results show that the leaves have relatively high concentrations of the alkaloids before flowering. The bulbs had lower concentrations of the compounds of interest but would have a higher total yield of alkaloids due to bigger biomass. Narcissus pseudonarcissus cv. Carlton represents a good source of galanthamine, and can potentially be a source of the other major alkaloids depending on choice of organ and harvest time
New Insights into an Ancient Antibrowning Agent: Formation of Sulfophenolics in Sodium Hydrogen Sulfite-Treated Potato Extracts
Narvaez Cuenca, C.E. ; Kuijpers, T.F.M. ; Vincken, J.P. ; Waard, P. de; Gruppen, H. - \ 2011
Journal of Agricultural and Food Chemistry 59 (2011)18. - ISSN 0021-8561 - p. 10247 - 10255.
tandem mass-spectrometry - chlorogenic acid - polyphenol oxidase - ascorbic-acid - quercetin - identification - inhibition - phenolics - oxidation - cysteine
The effect of sodium hydrogen sulfite (S), used as antibrowning agent, on the phenolic profile of potato extracts was investigated. This extract was compared to one obtained in the presence of ascorbic acid (A). In the presence of A, two major compounds were obtained, 5-O-caffeoylquinic acid (5-CQA) and 4-O-caffeoyl quinic acid. With S, their 2'-sulfo-adducts were found instead, the structures of which were confirmed by nuclear magnetic resonance spectroscopy and mass spectrometry. Also, for minor caffeoyl derivatives and quercetin glycosides, the corresponding sulfo-adducts were observed. Feruloyl and sinapoyl derivatives were not chemically affected by the presence of S. Polyphenol oxidase (PPO) was thought to be responsible for the formation of the sulfo-adducts. This was confirmed by preparing 2'-sulfo-5-O-caffeoyl quinic acid in a model system using 5-CQA, sodium hydrogen sulfite, and PPO. This sulfo-adduct exhibited a small bathochromic shift (¿max 329 nm) as compared to 5-CQA (¿max 325 nm) and a strong hypochromic shift with an extinction coefficient of 9357 ± 395 M–1 cm–1 as compared to 18494 ± 196 M–1 cm–1, respectively. The results suggest that whenever S is used as an antibrowning agent, the O-quinone formed with PPO reacts with S to produce sulfo-O-diphenol, which does not participate in browning reactions.
Sunflower proteins : overview of their physicochemical, structural and functional properties
González-Pérez, S. ; Vereijken, J.M. - \ 2007
Journal of the Science of Food and Agriculture 87 (2007)12. - ISSN 0022-5142 - p. 2173 - 2191.
helianthus-annuus l - seed storage proteins - low-molecular-weight - reduced soy glycinin - chlorogenic acid - foaming properties - ionic-strength - defatted sunflower - globulin fraction - oilseed proteins
There is increasing worldwide demand for proteins of both animal and plant origin. However, animal proteins are expensive in terms of both market price and environmental impact. Among alternative plant proteins, sunflower seeds are particularly interesting in view of their widespread availability in areas where soy is not or only sparsely produced. Compared with other sources of vegetable proteins, sunflower seeds have been reported to have a low content of antinutritional factors. Although the absence of these factors is important, the functionality of the protein preparations will mainly determine their applicability. This review provides detailed information about sunflower seed composition and processing, including processes to remove phenolic compounds from meals. The main part of the review concerns the structure and functionality of the two major protein fractions, helianthinin and 2S albumins. Regarding functionality, emphasis is on solubility, thermal behaviour and surface activity. Protein structure and functionality are discussed as a function of extrinsic factors such as pH, ionic strength, temperature and the presence of other seed components, particularly chlorogenic acid. In addition, sunflower proteins are compared from a structural and functional point of view with other plant proteins, particularly soy proteins.
Interactions of phenolic compounds with globular proteins and their effects on food-related functional properties
Prigent, S.V.E. - \ 2005
University. Promotor(en): Fons Voragen; Harry Gruppen, co-promotor(en): G.A. van Koningsveld. - Wageningen : - ISBN 9085042674 - 132
globulinen - eiwitten - fenolverbindingen - chlorogeenzuur - interacties - fysicochemische eigenschappen - fysische eigenschappen - voedsel - globulins - proteins - phenolic compounds - chlorogenic acid - interactions - physicochemical properties - physical properties - food
In order to modulate the functional properties of food proteins, the interactions between globular proteins and the monomeric phenolic, caffeoylquinic acid (CQA, chlorogenic acid), and the oligomeric phenolics, procyanidins, were characterized and investigated for their effect on protein functional properties. Non-covalent interactions between proteins and CQA involved a low affinity and did not affect protein solubility. Proteins show a medium affinity for procyanidins of an average degree of polymerization (DP) of 5.5, but weakly interacted with smaller procyanidins. Procyanidins of DP 5.5 strongly decreased protein solubility. Covalent interactions between proteins and CQA oxidised by polyphenol oxidase (PPO) or oxidised at alkaline pH resulted in protein modification mainly via dimeric CQA quinones. The covalent modifications of proteins with CQA strongly reduced protein solubility. Lysine, tyrosine, histidine and tryptophan were able to interact with CQA quinones. It can be concluded that for food non-covalent interactions are restricted to oligomeric phenolic.
Formation and Stability of Foams Made with Sunflower (Helianthus annuus) Proteins
Gonzalez-Perez, S. ; Vereijken, J.M. ; Koningsveld, G.A. van; Gruppen, H. ; Voragen, A.G.J. - \ 2005
Journal of Agricultural and Food Chemistry 53 (2005)16. - ISSN 0021-8561 - p. 6469 - 6476.
seed storage proteins - functional-properties - defatted sunflower - oilseed proteins - chlorogenic acid - soy glycinin - albumin - meal - isolate - whey
Foam properties of a sunflower isolate (SI), as well as those of helianthinin and sunflower albumins (SFAs), were studied at various pH values and ionic strengths and after heat treatment. Less foam could be formed from helianthinin than from SFAs, but foam prepared with helianthinin was more stable against Ostwald ripening and drainage than foam prepared with SFAs. Foams made with SFAs suffered from extensive coalescence. The formation and stability of foams made from reconstituted mixtures of both proteins and from SI showed the deteriorating effect of SFAs on foam stability. Foam stability against Ostwald ripening increased after acid and heat treatment of helianthinin. Partial unfolding of sunflower proteins, resulting in increased structural flexibility, improved protein performance at the air/water interface. Furthermore, it was observed that the protein available is used inefficiently and that typically only ~20% of the protein present is incorporated in the foam.
Emulsion properties of sunflower (Helianthus annuus) proteins
Gonzalez-Perez, S. ; Koningsveld, G.A. van; Vereijken, J.M. ; Merck, K.B. ; Gruppen, H. ; Voragen, A.G.J. - \ 2005
Journal of Agricultural and Food Chemistry 53 (2005)6. - ISSN 0021-8561 - p. 2261 - 2267.
seed storage proteins - functional-properties - physicochemical properties - emulsifying properties - charge heterogeneity - globulin fraction - chlorogenic acid - soy proteins - albumin - meal
Emulsions were made with sunflower protein isolate (SI), helianthinin, and sunflower albumins (SFAs). Emulsion formation and stabilization were studied as a function of pH and ionic strength and after heat treatment of the proteins. The emulsions were characterized with respect to average droplet size, surface excess, and the occurrence of coalescence and/or droplet aggregation. Sunflower proteins were shown to form stable emulsions, with the exception of SFAs at neutral and alkaline pH values. Droplet aggregation occurred in emulsions made with SI, helianthinin, and SFAs. Droplet aggregation and subsequent coalescence of emulsions made with SFAs could be prevented at pH 3. Calcium was found to cause droplet aggregation of emulsions made with helianthinin, at neutral and alkaline pH values. Treatments that increase conformational flexibility of the protein molecule improved the emulsion properties of sunflower proteins.
Physicochemical properties of 2S Albumins and the corresponding protein isolate from Sunflower (Helianthus annuus)
Gonzalez-Perez, S. ; Vereijken, J.M. ; Koningsveld, G.A. van; Gruppen, H. ; Voragen, A.G.J. - \ 2005
Journal of Food Science 70 (2005)1. - ISSN 0022-1147 - p. C98 - C103.
low-molecular-weight - methionine-rich - storage protein - functional-properties - chlorogenic acid - brassica-napus - seed proteins - napin - heat - solubility
Sunflower albumins (SFAs) are a diverse group of proteins present in sunflower isolates, with a sedimentation coefficient of approximately 2S. This research presents a detailed study of the influence of pH on the structure and solubility of SFAs. The effect of temperature on the structure of SFAs was also studied. Furthermore, the solubility of a sunflower isolate (SI) was studied and discussed in terms of its main protein components (SFAs and helianthinin). The native structure of SFAs revealed to be very stable against pH changes (pH 3.0 to 9.0) and heat treatment (>100 °C), and their solubility was only marginally affected by pH and ionic strength. The solubility of the sunflower isolate as a function of pH seems to be dominated by that of helianthinin: SI (I = 30 mM) showed a U-shaped solubility curve with a minimum between pH 4.0 and pH 6.0.
The apple skin: colourful healthiness : developmental and environmental regulation of flavonoids and chlorogenic acid in apples
Awad, M.A.G. - \ 2001
University. Promotor(en): W.M.F. Jongen; L.H.W. van der Plas; A. de Jager. - S.l. : S.n. - ISBN 9789058084255 - 146
malus - appels - chemische samenstelling - plantenpigmenten - flavonoïden - chlorogeenzuur - rijp worden - plantenontwikkeling - houdbaarheid (kwaliteit) - gasbewaring - apples - chemical composition - plant pigments - flavonoids - chlorogenic acid - ripening - plant development - keeping quality - controlled atmosphere storage
<p>The ultimate objective of the production, handling and distribution of fresh fruits and vegetables is to satisfy consumers requirements. In general the attractiveness of fruits and vegetables to consumers is determined both by visible (e.g. colour) and invisible (e.g. healthiness) quality attributes. Flavonoids and hydroxycinnamic acid derivatives, secondary metabolites, contribute largely to both fruit colour and, through fruit consumption, to human health and it is, therefore, very useful to study factors that affect these substances with the aim of further improving the relevant fruit attributes. Flavonoids and hydroxycinnamic acid derivatives are widespread in the plant kingdom, comprise a large group of naturally occurring antioxidants that form part of the human diet. There is considerable evidence for the role of antioxidant constituents of fruits and vegetables in the maintenance of health and disease prevention. Recent studies have shown that the majority of the antioxidant activity of a fruit or vegetable may originate from the flavonoids and other phenolic compounds. Apple fruit are rich in flavonoids such as flavonols (quercetin 3-glycosides), flavanols (catechin, epicatechin, gallocatechin, procyanidins and its polymers), dihydrochalcone glycosides (phloritin glucoside (phloridzin) and phloritin xyloglucoside), and cyanidin 3-glycoside (anthocyanins). Apple fruits also contain considerable amounts of hydroxycinnamic acid derivatives mainly represented by chlorogenic acid. The red colour of apples is primarily a consequence of the flavonoid pigments anthocyanins which are located in the vacuole. Despite the importance of flavonoids for the intrinsic quality of apples very little is known of their regulation in fruit. The aim of the work described in this thesis was therefore, to obtain knowledge on the extent to which the contents of flavonoids and chlorogenic acid in the skin of apples varies, how they develop during fruit growth phase, ripening phase and post harvest phase and how they can be manipulated.</p><p>Chapter 1 contains a review of the literature. It appears that the accumulation of flavonoids and phenolic acids in plants is under control of many internal and external factors.</p><p>In Chapter 2 the extent of natural variation in flavonoids and chlorogenic acid concentration due to within fruit, within tree, between orchards, between cultivars and among mutants was determined. Considerable variation was observed among these variables. Individual flavonoids and chlorogenic acid concentrations were not equally distributed within the fruit. Quercetin 3-glycosides and anthocyanin were almost exclusively found in the skin. The sun-exposed skin of individual fruit had much higher cyanidin 3-galactoside (anthocyanin) and quercetin 3-glycoside concentrations than the shaded skin, while phloridzin, catechins and chlorogenic acid were similar in the skin of both sides (Chapter 2). Significant genotypic variation was observed for the concentration of flavonoids and chlorogenic acid. 'Jonagold' apples contain significant higher concentrations (about 30% higher) (Chapters 2 and 6) and amounts (about 2-fold higher) (Chapter 6) of the total flavonoids than 'Elstar' apples. Chlorogenic acid concentration was about 3-fold higher in 'Jonagold' than in 'Elstar' apples. However 'Elstar' apples contained significant higher concentrations of some quercetin glycosides types as quercetin 3-rhamnoglucoside (about 2-fold higher) and quercetin 3-glucosides (about 30% higher) than 'Jonagold' apples. This might be relevant with respect to differences in bio-activity and antioxidant capacity of various flavonoid compounds. As far as the potential maximum concentration of flavonoids in apple is genetically determined breeding would be an important tool for increasing healthiness of apples. The differences between basic forms and coloured mutants within a given cultivar (for example Jonagold-Jonaprince; Elstar-Elshof) show that the potential anthocyanin accumulation (but only that) may increase several fold without influencing the concentrations of other flavonoid classes (Chapter 2). Microscopic study showed that the most blushed mutants had a higher number of red cells per cell layer and more cell layers containing red cells than the standard cultivar and the less blushed mutants. It is striking to observe coloured and completely uncoloured cells as neighbours. Since the selection of coloured mutants is inherently based on the amount of red coloration, selection of mutants for higher levels of other potential healthy flavonoid classes e.g. quercetin 3-glycosides could be considered, providing that such characteristics can be relatively easily determined. The concentrations of anthocyanin, quercetin 3-glycosides and total flavonoids were highest in fruit borne in the top of the tree followed by fruit from the outer tree parts, whereas the lowest concentrations were found in fruit from the inner tree. Terminal fruit contained the highest concentrations of these compounds, including catechins, compared to lateral and spur fruit. Phloridzin and chlorogenic acid were not affected by the position of the fruit in the tree nor by the bearing wood type. The maximum possible difference in flavonoid concentrations, based on difference between top fruit (optimal light conditions) and inner fruit (minimal light conditions) may be 3-fold for quercetin 3-glycosides and 2-fold for total flavonoids (Chapters 2 and 3). There were significant differences in flavonoid and chlorogenic acid concentrations in 'Elstar' fruit between two normally productive orchards differing mainly in growth vigour and internal shading. All these results show that light conditions are a main regulatory factor in the biosynthesis of flavonoids in apples.</p><p>In Chapter 3 the natural distribution of light within the tree canopy in relation to the concentration of flavonoids and chlorogenic acid in fruit skin was analysed. The concentrations of cyanidin 3-galactoside and quercetin 3-glycosides and the percentage of blush in the fruit skin were directly related to light level in the direct vicinity of the fruit. Light in the interior of the canopy was poorer in UV-A, blue, green and red (R) but richer in far-red (FR) light than at all other positions. Consequently, the FR/R ratio (with large influence on formative processes) was much larger at the interior of the canopy than at all other positions. There was a critical FR/R ratio of about 1 above which no anthocyanin and only low amounts of quercetin 3-glycosides were formed.</p><p>In Chapter 4 the relationships between the fruit nutrients N, P, K, Ca and Mg and concentrations of flavonoids and chlorogenic acid in fruit skin were studied with two types of 'Elstar'. In an experiment with the mutant 'Elshof' with the 5 nutrients applied at 5 rates in 4 replications, only N and Ca applications resulted in higher concentration of these nutrients in the fruit, but sufficient variation was present among treatments to correlate the concentration of the other nutrients with those of flavonoids and chlorogenic acid. Negative correlations were frequently found between the concentration of N and Mg and the N/Ca ratio in fruit during growth, and anthocyanin and total flavonoids concentration at maturity in 1996, 1997 and 1998. In 1997, these correlations were weakest but still significant. In that season, P and K concentration were frequently negatively correlated with the concentration of anthocyanin and total flavonoids. The concentration of Ca was not related to the concentration of anthocyanin and total flavonoids. In a study in 1996 with standard 'Elstar', we used the variation in nutrient concentration due to differences in fruit position on tree. The concentrations of N and K and the N/Ca ratio in fruit at maturity were negatively and that of Ca was positively correlated with the concentration of anthocyanin and total flavonoids. Magnesium concentration was negatively correlated with anthocyanin concentration but not with total flavonoids. As a consequence of the relation with position of the fruit in the tree an interaction with the influence of light may, however, be expected. Multiple regression models mainly containing N as factor accounted for up to 40% and 30% of the variance in anthocyanin and total flavonoids concentration of 'Elshof' mutant apples, and for up to 70% and 65% of the variance in anthocyanin and total flavonoids concentration of standard 'Elstar' apples. The relationships between plant nutrients and chlorogenic acid concentration in apples were not consistent and further study is required. It is concluded that, in addition to improving light conditions, the concentration of flavonoids in fruit skin could be further increased by optimising fertilization especially that of N, directed at preventing excess N accumulation.</p><p>In Chapter 5 we tested the concept that under condition of high carbon supply, plants may increase the formation of their secondary metabolites, like phenolic compounds. In field experiments crop load was manipulated by applying flower or fruit thinning at different stages of development and at different severity. At a low crop load, fruit weight, soluble solids, acidity and firmness were significantly higher than at high and moderate loads. However, the concentrations of flavonoid and chlorogenic acid were similar at the different levels of crop load. Time of thinning had no significant influence on the concentration of flavonoids and chlorogenic acid in fruit skin and had no further effect on fruit quality characteristics such as weight, soluble solids, acidity and firmness. Removal of only the interior fruits (about one-third of total fruit) at about 4 weeks before expected commercial harvest had no influence on the concentration of flavonoids and chlorogenic acid or on the quality characteristics of the remaining exterior fruits of either 'Elstar' or 'Jonagold'. The results indicate that, within the 'normal' range of conditions, assimilate availability is not a major regulatory factor in flavonoids and chlorogenic acid formation in apples. These results are in agreement with the lack of any influence of the supply of precursors in the orchard (Chapter 7).</p><p>In Chapter 6 the changes that take place in the concentration and the amount of individual flavonoids and chlorogenic acid in the skin of 'Elstar' and 'Jonagold' apples during development and ripening were investigated. In both cultivars, the concentration on a dry weight basis of quercetin glycosides, phloridzin and chlorogenic acid was highest early in the season but decreased at different rates during fruit development to reach a steady level during maturation and ripening. Catechins (catechin plus epicatechin) concentration showed a similar pattern, but a temporary increase was observed in an early stage of development. The concentration of cyanidin 3-galactoside (anthocyanin) was relatively high early in the season, gradually decreased to a very low steady level during growth, but started to increase near maturation, especially in the outer fruit. On a fruit basis the amount of quercetin glycosides increased during development and was about two times higher in 'Jonagold' compared to 'Elstar', both in outer and inner fruit. These compounds were the most abundant flavonoids in the skin of both cultivars and their accumulation showed a strong dependency on fruit position on tree. The amount of the second most abundant flavonoid type, catechins, increased during development to a maximum and then showed some decrease by mid season which was independent of fruit position on tree. The amount of phloridzin increased only early in the season reaching a steady level during development and ripening, and was independent of fruit position on tree. The amount of chlorogenic acid in both cultivars initially increased, but subsequently decreased to reach a low steady level and was slightly higher in outer than in inner fruit. The latter phenomenon is the only direct evidence for (net) breakdown of any of the studied phenolics. Although anthocyanin concentration was relatively high at early stages of development, significant accumulation on a fruit basis only occurred during maturation and ripening. The accumulation of anthocyanin, similar to that of quercetin glycosides, showed a strong dependency on fruit position on tree. The results indicate that, in general, the overall production of total flavonoids, with the exception of anthocyanin, and chlorogenic acid in apple skin is completed during fruit development before the onset of maturation.</p><p>Chapter 7 reports the influence of exogenous application of a number of chemicals that are precursors of flavonoids or are known to affect ripening on the accumulation of flavonoids and chlorogenic acid in 'Jonagold' apple skin with emphasis on anthocyanin. One aim was to identify a possible substrate limitation and another to separate the formation of anthocyanin from other related maturity/ripening events. Since the occurrence of the second peak in anthocyanin formation more or less parallels the maturation and ripening phase (like starch degradation and aroma production), anthocyanin formation itself is often considered as a ripening phenomenon triggered by ethylene. Our results suggest, however, that there is no simple relation to ripening and consequently to ethylene production (though we did not measure ethylene). This is concluded from the promotion of anthocyanin formation by ethephon (an ethylene releasing compound) and the retardation of anthocyanin formation by ABG and GA <sub>3</sub> (known to lower or counteract endogenous ethylene), without significantly altering starch degradation and changes in streif index (combination of starch index, firmness and sugar concentration). Our results have also shown that the other flavonoid classes quercetin 3-glycosides, catechins and phloridzin and chlorogenic acid do not respond to any of the applied chemicals. It is concluded that anthocyanin formation is dependent on developmental signals and independent of both fruit maturity/ripening and of the synthesis of other flavonoid classes and responds in a complicated way to ethylene.</p><p>In Chapter 8 the changes in individual flavonoids and chlorogenic acid during regular (RS) or ultra low oxygen (ULO) storage conditions at 1°C are reported in both 'Jonagold' and 'Elstar' apples. It could convincingly be shown that during storage of both 'Jonagold' (3, 6 and 8 months) and of 'Elstar' (2, 4 and 6 months) and during 1 or 2 weeks shelf life, the concentrations of cyanidin 3-galactoside and quercetin glycosides were relatively constant, while the concentrations of catechins, phloridzin and chlorogenic acid showed only minor decreases. Moreover there were no significant differences in the concentration of flavonoids and chlorogenic acid between fruits stored under ULO compared to RS conditions. It is concluded that, following harvest, flavonoids present in apples are stable. There is no direct or indirect proof for breakdown (net metabolic turnover) during storage and shelf life.</p><p>In Chapter 9 the practical applications of the findings made in this study were discussed. Our results show that there is much room for increasing the level of potential health phytochemicals in apples. The first step would be cultivar selection either from already available genotypes or by developing new cultivars through classical breeding or molecular biology and gene technology. We showed that light has a significant impact on the final level of flavonoids in fruit. Therefore, the second and more proximate option would be the optimisation of light conditions within tree canopy by measures such as choice of root stocks, planting system, row orientation and training and pruning systems or covering the orchard floor with reflecting films (though the latter is not promoting the visual aspect of the orchard). A third step could be optimisation of the fertilization programme especially avoiding excess N and better timing of N-application. A further possibility is to sort fruit in healthiness classes. As long as a simple method to detect non-destructively quercetin 3-glycosides is lacking, sorting of fruit based on their blush might be a way to make healthiness classes, since blush is a good marker for exposure to light during growth and thus to some extent for the quercetin 3-glycosides level. Even when cultivar choice and cultivation methods succeed in getting high levels of flavonoids in fruit still the treatment by the consumer determines how much of these substances will be consumed. Many consumers still peel the fruit before consumption thereby removing almost all anthocyanin and quercetin 3-glycosides (Chapter 2). Promotion of fruit on the basis of healthiness is, in our opinion, however, only useful if it is accompanied with a guarantee of absence of pesticides, as is most credible, at least to the public, in organic farming.</p><p>Because of the large influence of a number of factors at several steps of the production chain, a quantitative model e.g. integrated with light distribution models, would offer a practical and effective tool for estimating the effect of certain measures and to predict and maximise the final level of healthy compounds in apples enabling the development of more accurate intake data and dietary recommendations.</p>
Bioavailability of flavonoids and cinnamic acids and their effect on plasma homosysteine in humans
Olthof, M.R. - \ 2001
University. Promotor(en): M.B. Katan; Peter Hollman. - S.l. : S.n. - ISBN 9789058084170 - 135
flavonoïden - kaneelzuur - homocysteïne - bloedplasma - biologische beschikbaarheid - mens - quercetine - theaflavine - chlorogeenzuur - hart- en vaatziekten - flavonoids - cinnamic acid - homocysteine - blood plasma - bioavailability - man - quercetin - chlorogenic acid - cardiovascular diseases
<p>Dietary antioxidants might prevent oxidative damage to tissues and therefore protect against cardiovascular disease and cancer. Dietary phenols are strong antioxidants in vitro but their role in vivo is uncertain. Furthermore, there are only limited data on their bioavailability in humans. The aim of this thesis was to investigate <em>whether bioavailability data on flavonoids and cinnamic acids support the hypothesis that they can affect health in humans</em> . Because the group of phenols in foods is huge, we focussed our research on major phenols in foods; the flavonol quercetin, black tea phenols and chlorogenic acid (5-caffeoylquinic acid). We studied their bioavailability and effect on plasma homocysteine in humans, a potential risk factor for cardiovascular disease.</p><p>The bioavailability of quercetin and chlorogenic acid depends upon their conjugated moieties. Hollman et al. found that the bioavailability of quercetin-3-rutinoside, a major flavonol in tea, was only 20% of that of quercetin-4'-glucoside. We found that transformation of quercetin-3-rutinoside into quercetin-3-glucoside will improve its bioavailability because the 3-glucoside had the same high bioavailability as the 4'-glucoside. Caffeic acid is a major phenol in coffee, but it is present as a conjugate with quinic acid, called chlorogenic acid. We found that the conjugation of caffeic acid with quinic acid hinders absorption in humans: absorption of chlorogenic acid was only 30% of that of its caffeic acid moiety.</p><p>Furthermore, we found that chlorogenic acid, black tea solids and quercetin-3-rutinoside are extensively metabolized in the human body, mainly before they reach the circulation. Their metabolites have no, or less, antioxidant activity in vitro than their parent phenols. Therefore the role of dietary phenols as antioxidants in vivo might be less important than suggested by their in vitro antioxidant activity.</p><p>Coffee consumption increases plasma homocysteine, a potential risk factor for cardiovascular disease. Chlorogenic acid from coffee is partly responsible for the homocysteine-raising effect of coffee, because we found that it increased plasma homocysteine. Black tea solids also raised plasma homocysteine, whereas quercetin-3-rutinoside did not. Furthermore, we found that glycination of metabolites of phenols in the body is not involved in the homocysteine-raising effect of phenols.</p><p>In conclusion, chlorogenic acid, tea phenols and quercetin are available in the human body, but their effects on health are uncertain. Further research on bioavailability and health effects of dietary phenols is needed.</p>
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