Foods, phenolic acids

Knowledge of the identity of phenolic compounds in food facilitates the analysis and discussion of potential antioxidant effects. Thus studies of phenolic compounds as antioxidants in food should usually by accompanied by the identification and quantification of the phenols. Reversed-phase HPLC combined with UV-VIS or electrochemical detection is the most common method for quantification of individual flavonoids and phenolic acids in foods (Merken and Beecher, 2000 Mattila and Kumpulainen, 2002), whereas HPLC combined with mass spectrometry has been used for identification of phenolic compounds (Justesen et al, 1998). Normal-phase HPLC combined with mass spectrometry has been used to identify monomeric and dimeric proanthocyanidins (Lazarus et al, 1999). Flavonoids are usually quantified as aglycones by HPLC, and samples containing flavonoid glycosides are therefore hydrolysed before analysis (Nuutila et al, 2002). 

MATTILA p and KUMPULAINEN J (2002) Determination of free and total phenolic acids in plant-derived foods by HPLC with diode-array detection, JAgric Food Chem, 50, 3660-67. 

NUUTILA A M, KAMMioviRTA K and OKSMAN-CALDENTEY K-M (2002) Comparison of methods for the hydrolysis of flavonoids and phenolic acids from onion and spinach for HPLC-analysis, Food Chem, 76, 519-25. 

Hakkinen S H and Torronen A R (2000), Content of flavonols and selected phenolic acids in strawberries and vaccinium species influence of cultivar, cultivation site and technique , Food Res Int, 33, 517-524. 

Mpofu A, Sapirstein HD, and Beta T (2006), Genotype and environmental variation in phenolic content, phenolic acid composition, and antioxidant activity of hard spring wheat , J Agric Food Chem, 54, 1265-1270. 

Food and plant phenolics are commonly detected using DAD detectors (Tan and others 2008). Photodiode array detection allows collection of the entire UV spectrum during the elution of a chromatographic peak, which makes it possible to identify a phenolic compound by its spectra. Simple phenols, phenolic acids, flavanones, benzophenones, isoflavones, and flavan-3-ols have maximum absorbance at 280 nm, hydroxycinnamic acids at 320 nm, flavonols, flavones, and dihydroflavonols at 365 nm, and anthocyanins at 520 nm (Ibern-G6mez and others 2002 Merken Hand Beecher 2000). Hydrolyzable tannins show a characteristic shoulder at 300 nm, suitable for identifying them (Arapitsas and others 2007). For stilbenes, maximum absorbance of trans-forms are at 306 nm and at 285 nm for cA-forms (Lamuela-Raventos and others 1995). 

The Folin-Ciocalteu assay is the most widely used method to determine the total content of food phenolics (Fleck and others 2008). Folin-Ciocalteu reagent is not specific and detects all phenolic groups found in extracts, including those found in extractable proteins. A disadvantage of this assay is the interference of reducing substances, such as ascorbic acid (Singleton and others 1999). The content of phenolics is expressed as gallic acid or catechin equivalents. 

Colaric M, Veberic R, Solar A, Hudina M and Stampar F. 2005. Phenolic acids, syringaldehyde, and juglone in fruits of different cultivars of Juglans regia L. J Agric Food Chem 53(16) 6390-6396. 

Floridi S, Montanari L, Marconi O and Fantozzi P. 2003. Determination of free phenolic acids in wort and beer by coulometric array detection. J Agric Food Chem 51(6) 1548—1554. 

Mane C, Souquet JM, Olle D, Verries C, Veran F, Mazerolles G, Cheynier V and Fulcrand H. 2007. Optimization of simultaneous flavanol, phenolic acid, and anthocyanin extraction from grapes using an experimental design application to the characterization of champagne grape varieties. J Agric Food Chem 55(18) 7224—7233. 

Mattila P, Hellstrom J and Torronen R. 2006. Phenolic acids in berries, fruits, and beverages. J Agric Food Chem 54(19) 7193—7199. 

Robbins RJ. 2003. Phenolic acids in foods An overview of analytical methodology. J Agric Food Chem 51(10) 2866-2887. 

Truong VD, McFeeters RF, Thompson RT, Dean LL and Shofran B. 2007. Phenolic acid content and composition in leaves and roots of common commercial sweetpotato (Ipomea batatas L.) cultivars in the United States. J Food Sci 72(6) C343-C349. 

Zadernowski R, Czaplicki S and Naczk M. 2009. Phenolic acid profiles of mangosteen fruits (Garcinia mangostana). Food Chem 112(3) 685-689. 

NprbaskR, Aaboer DB, Bleeg IS, Christensen BT, Kondo T, Brandt K (2003) Flavone C-glycoside, phenolic acid, and nitrogen contents in leaves of barley subject to organic fertilization treatments. J Agric Food Chem 51 809-13... 

L. Yao, N. Datta, F. A. Tomas-Barberan, F. Ferreres, I. Martos and R. Singanusong, Flavonoid, phenolic acids and abscisic acid in Australian and New Zealand Leptospermum honeys. Food Chem. 81 (2003) 159-168. 

L. Yao, Y. Jiang, N. Datta, R. Singanusong, X. Liu, J.Duan, K. Raymont, A. Lisle and Y. Xu, HPLC analyses of flavanols and phenolic acids in the fresh shoots of tea (Camellia sinensis) grown in Australia. Food Chem. 84 (2004) 253-263. 

Vaughan D, Ord B. 1990. Influence of phenolic acids on morphological changes in roots of Pisum sativum. Journal of the Science of Food and Agriculture 52 289-299. 

Silva, E. A. M. Borges, E Gulmaraes, C. Lima,]. L. F. C. Matos, C. Reis, S. Phenolic Acids and Derivatives Studies on the Relationship among Structure, Radical Scavenging Activity, and Physicochemical Parameters.]. Agric. Food Chem. 2000, 48, 2122-2126. 

FIGURE 19.9 HPLC chromatogram of standards of phenolic acids, flavonols, flavones, and glycosides isolated in onions and spinach. (From Nnntila, A.M. et al., Food Chem., 76, 519, 2002. Copyright 2002. With permission from Elsevier.)... 

Torronen, R. et al., Flavonoids and phenolic acids in selected berries. Cancer Lett., 114, 191, 1997. Arts, I.C.W., van de Putte, B., and Hollman, P.C.H., Catechin contents of foods commonly consumed in The Netherlands. 2. Tea, wine, fruit juices, and chocolate milk, J. Agric. Food Chem., 48, 1752, 2000. 

Radtke, J., Linseisen, J., and Wolfram, G., Phenolic acid intake of adults in a Bavarian subgroup of the national food consumption survey, Z. Erndhrungswiss., 37, 190, 1998. 

Nardini, M., Cirillo, E., Natella, F., and Scaccini, C., Absorption of phenolic acids in humans after coffee consumption, J. Agric. Food Chem., 50, 5735, 2002. 

Konishi, Y., Kobayashi, S., and Shimizu, M., Tea polyphenols inhibit the transport of dietary phenolic acids mediated by the monocarboxylic acid transporter (MCT) in intestinal Caco-2 cell monolayers, J. Agric. Food Chem., 51, 7296, 2003. 

The cited observations suggest that it is possible to identify potato cultivars with low or high phenolic acid content for human use and to select processing conditions that minimize losses of phenolic compounds. In summary, the methods we developed and used to determine the content and distribution of phenolic compounds in potato plant flowers, leaves, and tubers, in the peel and flesh parts of potato tubers, and in freeze-dried and processed commercial potatoes merit application in numerous studies designed to assess the role of potato phenolic compounds in host-plant resistance, plant breeding, plant molecular biology, food chemistry, nutrition, and medicine. The described wide distribution of phenolic compounds in different commercial... 

Mattila, P., Hellstrom, J. (2007). Phenolic acids in potatoes, vegetables, and some of their products. J. Food Compos. Anal., 20, 152-160. 

Lewis, C. E., Walker, J. R. L., Lancaster, J. E., Sutton, K. H. (1998). Determination of anthocyanins, flavonoids and phenolic acids in potatoes. I. Coloured cultivars of Solanum tuberosum L. Journal of the Science of Food and Agriculture, 77,45-57. 

Torres, A.M., Mau-Lastovicka, T., and Rezaaiyan, R. 1987. Total phenolics and high-performance liquid chromatography of phenolic acids of avocado. J. Agric. Food Chem. 35 921-925. 

Reversed-phase chromatography is the most popular mode of analytical liquid chromatography for phenolic compounds. In most cases, the reported systems for the separation of phenolics and their glycosides in foods are carried out on reversed-phase chromatography on silica-based Cl8 bonded-phase columns. Occasionally, silica columns bonded with C8 were applied in the analysis of phenolic acid standards and coumarins (7), and C6 columns for the analysis of ferulic acid in wheat straw (8). 

---