POLISH JOURNAL OF FOOD AND NUTRITION SCIENCES Pol. J. Food Nutr. Sci. 2005, Vol. 14/55, No 2, pp. 165–170 COMPARISON OF RADICAL-SCAVENGING ACTIVITIES FOR SELECTED PHENOLIC ACIDS Magdalena Karamaæ 1 , Agnieszka Kosiñska 1 , Ronald B. Pegg 2 1 Institute of Animal Reproduction and Food Research of the Polish Academy of Sciences, Division of Food Science, Olsztyn, Poland; 2 Department of Applied Microbiology and Food Science, University of Saskatchewan, Saskatoon, Canada Key words: phenolic acids, radical-scavenging activity, DPPH • The capacity of selected phenolic acids (i.e. gallic, salicylic, p-hydroxybenzoic, gentisic, protocatechuic, vanillic, syringic, o-, m-, p-coumaric, caffeic, ferulic, isoferulic, and sinapic acids) to scavenge the “stable” free radical 2,2-diphenyl-1-picrylhydrazyl • (DPPH • ) was evaluated using the classical assay. Compounds tested with this method demonstrated radical-scavenging activities to vary to a different extent, but in a concentration- -dependent manner. Gallic and gentisic acids showed the strongest antiradical properties (EC 50 0.0237 and 0.0292 μmol/assay, respectively) where- as salicylic and p-hydroxybenzoic acids were the least active radical scavengers (EC 50 > 800 μmol/assay). INRTODUCTION Benzoic and cinnamic acid derivatives are phenolic com- pounds endogenous to cereal grains (e.g. barley, buckwheat, oats, soybean, rye, wheat), oilseeds (e.g. rapeseed/canola, mustard), pulses/legumes (e.g. field pea, mung bean, chick- peas, lentils), vegetables (e.g. asparagus, carrots), and a myr- iad of other plant species [Weidner et al., 1999; Weidner et al., 2000; Amarowicz et al., 1995; Naczk et al., 1998; Shahidi et al., 1994; Shahidi & Naczk, 2004]. The phenolic acids of plant material and those in food of plant origin exist in the free, esterified, glycosidic, and insoluble-bound forms [Sosulski et al., 1982; Hermann, 1989]. In cereals, for exam- ple, much of the ferulic acid is present as ester derivatives of the stanol and sterol type [Herrmann, 1989]: the highest con- centration of steroyl ferulates (i.e. g-oryzanol) has been reported in rice bran oil [Xu & Godber, 1999]. Of the phenolic acids, ferulic acid has received much attention. For example, the antioxidant effect of ferulic acid on the peroxidation of ghee during storage for 30 days at 37°C was observed by Gupta et al. [1979]. Yagi and Ohishi [1979] reported the antioxidant activity of g-oryzanol, a mix- ture of ferulic acid esters of triterpenoid alcohol. Toda et al. [1991] noted that ferulic acid scavenged the superoxide anion radical and inhibited lipid peroxidation induced by superoxide. A general review of the radical-scavenging activity of ferulates is presented by Graf [1992]. Brand- -Williams et al. [1995] evaluated the antiradical activity of several phenolic acids. The antioxidant activity of prepared extracts from canola, rapeseed, mustard, cereals, and legumes, in which phenolic acids were the dominant pheno- lic constituent, has been reported in several studies [Amarowicz et al., 1995; Amarowicz et al., 1996; Amarowicz et al., 2000; Amarowicz et al., 2002; Karamaæ et al., 2002]. More recently, Marinova and Yanishlieva [2003] reported on the antioxidant activity of some phenolic acids using bulk oil model systems. The aim of the present work was to compare the radical- -scavenging activities of 14 phenolic acids using DPPH rad- ical as a model system. MATERIALS AND METHODS Chemicals. Methanol of analytical grade was purchased from the P.O.Ch. Company (Gliwice, Poland). 2,2-diphenyl- -1-picrylhydrazyl • (DPPH • ), butylated hydroxyanisole and phenolic acid standards (i.e. gallic, salicylic, p-hydroxyben- zoic, gentisic, protocatechuic, vanillic, syringic, o-, m-, p- -coumaric, caffeic, ferulic, isoferulic, and sinapic) were obtained from the Sigma Chemical Co. Ltd. (Poznañ, Poland). The chemical structures of these phenolic acids are presented in Figure 1. Author’s address for correspondence: M. Karamaæ, Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, ul. Tuwi- ma 10, P.O. Box 55, 10-747 Olsztyn, Poland, tel.: (48 89) 523 46 27; fax: (48 89) 524 01 24; e-mail: magda@pan.olsztyn.pl C R 1 2 3 4 5 6 R 1 2 3 4 5 6 O OH C O OH Acids: Salicylic R: 2-OH p-Hydroxybenzoic R: 4-OH Gentistic R: 2,5-di-OH Protocatechuic R: 3,4-di-OH Gallic R: 3,4,5-tri-OH Vanillic R: 3-OCH 3 , 4-OH Syringic R: 3,5-di-OCH 3 , 4-OH Acids: o-Coumaric R: 2-OH m-Coumaric R: 3-OH p-Coumaric R: 4-OH Caffeic R: 3,4-di-OH Ferulic R: 3-OCH 3 , 4-OH Isoferulic R: 4-OCH 3 , 3-OH Sinapic R: 3,5-OCH 3 , 4-OH FIGURE. 1. Chemical structures of selected phenolic acids.