PHENOLIC COMPOUNDS IN FOOD

Transcription

1 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

2 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

3 Phenolics are compounds with at least one aromatic ring and at least one -OH group 3

4 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

5 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 fruits vegetables cereals seeds cocoa seasonings oils

6 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,

7 Resveratrol stilbene C6-C2-C6 - antioxidant in wine, peanuts 7

8 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

9 Red cabbage extract at low ph (left) to high ph (right)

10 Anthocyanin Content in Common Fruits Fruit Red Apple, Pear Amount (mg/100g) Pelargonidin Peonidin Cyanidin Delphinidin Malvidin Bilberry X X X X X X Blackberry , mostly 150 Blueberry X X X X Sweet X X Cherries Cranberry X X Peach X X Plum X Strawberry varies widely X X 10

11 Tannins = condensed + hydrolyzable tannins: Procyanidin B1 Epicatechin(4beta-->8)catechin Procyanidin B2 Epicatechin(4beta->8)epicatechin 11

12 pomegranate Bennick, CROBM 2002;13: persimon

13 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 Black currant 20.3 Red currant 12.6 Bilberry 29.7 Apple Red onion Tomato Carrot, flesh Pea Horseradish Hop mg GAE/g dw, mg gallic acid equivalents/g dry weight 2 Data from (Yanishlieva et al., 2006) 13

14 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 ( 14

15 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,

16 *MEP = metileritritol phosphate pathway 16

17 Phenolics biosynthesis Heldt (1999). Plant Biochemistry and Molecular Biology, Oxford University Press 17

18 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

19 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

20 EXAMPLE: extraction of anthocyanins from billberries 1) 50 g frozen bilberry 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

21 Billberries crude extract Sep-Pak C18 Phenolic acids Sephadex LH-20 Proanthocyanidins, flavanols Sep-Pak C18 Flavonols Anthocyanin fraction Može Bornšek, Doctoral Dissertation,

22 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.,

23 ANTIOXIDANT ACTIVITY 1. RADICAL scavengering 2. METAL IONS scavengering 3. LIPID PEOXYL RADICALS scavengering 4. INHIBITION of enzymes 23

24 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

25 ANTIMICROBIALS Sempervivum tectorum L. 25

26 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

27 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

28 28

29 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

30 THANK YOU FOR YOUR ATTENTION! 30