PHENOLIC COMPOUNDS IN FOOD Veronika Abram, Nataša Poklar Ulrih Ljubljana, 2012 Chair of Biochemistry and Chemistry of Foods, Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana 1
Phenolic compounds (phenolics) are secondary metabolites responsible for sensory properties of foods, like taste, color, aroma and texture (Shahidi and Naczk, 1995a; Batu, 2003) 2
Phenolics are compounds with at least one aromatic ring and at least one -OH group 3
PHENOLICS CLASIFICATION No. of C-atoms Basic skeleton Group 6 C6 phenols 7 C6-C1 phenolic acids 8 C6-C2 phenylacetic acids 9 C6-C3 hydroxycinnamic acids, phenylpropenes 10 C6-C4 naphtoquinones 13 C6-C1-C6 xantones 14 C6-C2-C6 stilbenes 15 C6-C3-C6 flavonoids 18 (C6-C3)2 lignans, neolignans 30 (C6-C3-C6)2 biflavonoids n (C6-C3)n lignines (C6)n melanins (C6-C3-C6)n condensed tannins 4 Goodwin in Mercer (1983). Introduction to Plant Biochemistry, 2. Izdaja, Oxford University Press
Number of polyphenols described in each food group (Perez-Jimenez et al., 2010) food group flavonoids phenolic acids stilbenes lignans other polyphenols nonalcoholic beverages alcoholic beverages 105 49 6 2 12 75 33 13 7 19 fruits 112 47 7 6 1 vegetables 92 51 0 6 12 cereals 33 29 0 6 2 seeds 76 16 3 18 4 cocoa 25 13 2 0 5 seasonings 62 29 1 0 25 oils 11 28 2 12 22 5
Phenolic acids: hydroxybenzoic, C6-C1, and hydroxycinnamic acids, C6-C3 gallic acid caffeic acid - various phenolic acids are found in bilberries, blueberries or other berries Može Bornšek et al. J.Agric. Food Chem. (2011), 59, 6998-7004 6
Resveratrol stilbene C6-C2-C6 - antioxidant in wine, peanuts 7
Flavonoids: Anthocyanins sugar = Anthocyanidins, C6-C3-C6, red, purple, and blue colors (many fruits, vegetables, cereal grains, and flowers) Anthocyanidin R1 R2 R3 Pelargonidin H OH H Cyanidin OH OH H Delphinidin OH OH OH Peonidin OCH 3 OH H Petunidin OCH 3 OH OH Malvidin OCH 3 OH OCH 3 8
Red cabbage extract at low ph (left) to high ph (right)
Anthocyanin Content in Common Fruits Fruit Red Apple, Pear Amount (mg/100g) Pelargonidin Peonidin Cyanidin Delphinidin Malvidin Bilberry 300-648 X X X X X X Blackberry 82-325, mostly 150 Blueberry 25-495 X X X X Sweet 350-450 X X Cherries Cranberry 50-80 X X Peach X X Plum X Strawberry varies widely X X 10
Tannins = condensed + hydrolyzable tannins: Procyanidin B1 Epicatechin(4beta-->8)catechin Procyanidin B2 Epicatechin(4beta->8)epicatechin 11
pomegranate Bennick, CROBM 2002;13:184-196 persimon
Table 1. The contents of phenolic compounds in some fruit and vegetables (Kahkoenen et al., 1999) Fruit/ vegetable Phenolics (mg GAE/g dw) 1 Strawberries 14.8-23.7 Black currant 20.3 Red currant 12.6 Bilberry 29.7 Apple 11.9 12.1 Red onion 2 3.0 Tomato 2 2.0 Carrot, flesh 2 0.6 Pea 2 0.4 Horseradish 2 0.9 Hop 2 23.1 1 mg GAE/g dw, mg gallic acid equivalents/g dry weight 2 Data from (Yanishlieva et al., 2006) 13
SOURCES OF PHENOLIC COMPOUNDS The most important because they consumed in large quantities: green and black tea, red wine, coffee, cocoa and chocolate A database with the contents of different phenolic compounds: INRA, France webpage (http://www.phenol-explorer.eu) 14
PHENOLICS BIOSYNTHESIS synthesized from eritrose 4-phoshate and phosphoenolpyruvate via aromatic amino acids (phenylalanine, tyrosine) to phenylpropanoids and then with malonyl-coa to flavonoids or other phenolic compounds Strack, 1997; Winkel-Shirley, 2002 15
*MEP = metileritritol phosphate pathway 16
Phenolics biosynthesis Heldt (1999). Plant Biochemistry and Molecular Biology, Oxford University Press 17
ISOLATION OF PHENOLICS the fact is that there is not only one solvent or solvent extraction mixture which would be able to extract each and every food phenolics Waterman and Simon 1994; Shahidi and Naczk 1995 18
A recommendation to a beginner: a mixture of water with one of the following solvents: methanol, ethanol or acetone. A 50 % methanol in water is a popular choice. Start with room temperature or in the cold room. Place a sample in a flask and add at least 100 times its volume of the extracting solvent, use a shaker to improve extraction and leave the extraction overnight. 19
EXAMPLE: extraction of anthocyanins from billberries 1) 50 g frozen bilberry + 150 ml of cooled methanol, extracted 3 h by shaking in the dark 2) centrifugation 3) repeat the extraction 4) centrifugation 5) both supernatants combined, saturated with nitrogen and stored at 20 C until analysis or further purification 20
Billberries crude extract Sep-Pak C18 Phenolic acids Sephadex LH-20 Proanthocyanidins, flavanols Sep-Pak C18 Flavonols Anthocyanin fraction Može Bornšek, Doctoral Dissertation, 2012 21
POTENTIAL APPLICATIONS good antioxidants antimicrobials interesting for food industry colorants anticarcinogenic compounds etc. Abram and Donko, 1999, Abram, 2000; Šentjurc et al., 2003; Klancnik et al., 2010 22
ANTIOXIDANT ACTIVITY 1. RADICAL scavengering 2. METAL IONS scavengering 3. LIPID PEOXYL RADICALS scavengering 4. INHIBITION of enzymes 23
ANTIOXIDANT ACTIVITY - S. tectorum Figure 2. KA = kaempferol, KG = kaempferol-3-glucoside, OP = oligomeric polyphenols from leaves of S. tectorum, STJA = juice squeezed from the leaves of S. tectorum in the presence of ascorbate oxidase (1000 U/mL), mix = mixture of KA, KG, malic acid and citric acid and CA = citric acid Šentjurc et al. (2003) J. Agric. Food Chem., vol. 51, no. 9, str. 2766-2771 24
ANTIMICROBIALS Sempervivum tectorum L. 25
Leaves of S. tectorum Figure 4. Growth inhibition: 1 - Bacillus cereus, 2 - Enterococcus faecalis, 3 - Proteus morgani, 4 - Escherichia coli, 5 - Staphylococcus aureus, 6 - Saccharomyces cerevisiae, 7 - Geotrichum sp. (Abram and Donko, 1999) 26
BIOAVAILABILITY the proportion of the nutrient that is digested, absorbed and metabolized through normal pathways TASK: up-to-date 502 Polyphenols in 452 foods 27
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Some conclusions (Može Bornšek et al., 2012): The results obtained indicate that the extracts of billberries are excellent intracellular antioxidants even at very low concentrations. There is the marked paradox of high bioactivity versus low bioavailability of anthocyanins. Rather, the daily intake of normal servings over a long time span deserves being considered in future intervention studies. 29
THANK YOU FOR YOUR ATTENTION! 30