Antioxidant properties of ferulic acid and its related compounds

Antioxidant activity of 24 ferulic acid related compounds together with 6 gallic acid related compounds was evaluated using several different physical systems as well as their radical scavenging activity. The radical scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH) decreased in the order caffeic acid > sinapic acid > ferulic acid > ferulic acid esters > p-coumaric acid. In bulk methyl linoleate, test hydroxycinnamic acids and ferulic acid esters showed antioxidant activity in parallel with their radical scavenging activity. In an ethanol-buffer solution of linoleic acid, the activity of test compounds was not always associated with their radical scavenging activity. Ferulic acid was most effective among the tested phenolic acids. Esterification of ferulic acid resulted in increasing activity. The activity of alkyl ferulates was somewhat influenced by the chain length of alcohol moiety. When the inhibitory effects of alkyl ferulates against oxidation of liposome induced by AAPH were tested, hexyl, octyl, and 2-ethyl-1-hexyl ferulates were more active than the other alkyl ferulates. Furthermore, lauryl gallate is most effective among the tested alkyl gallates. These results indicated that not only the radical scavenging activity of antioxidants, but also their affinity with lipid substrates, might be important factors in their activity.     

Steryl phenolic acid esters in cereals and their milling fractions

The steryl ferulate contents of rye and wheat grains and their milling fractions were analyzed using a reversed-phase high-performance liquid chromatographic (HPLC) method. HPLC-mass spectrometry was used for identification. In addition, steryl ferulates of some selected milling byproducts were determined. The total steryl ferulate contents of rye and wheat grains were 6.0 and 6.3 mg/100 g, respectively. Uneven distribution of steryl ferulates in the grains led to considerable differences in the milling products; their steryl ferulate contents ranged from trace amounts in flours with low ash content to 20 and 34 mg/100 g in rye and wheat brans, respectively. Campestanyl ferulate and sitostanyl ferulate were the main components, followed by campesteryl ferulate and sitosteryl ferulate, whereas sitosterol was the main component in total sterols. Among the other samples, a byproduct of rice milling (pearling dust) was the best source of steryl ferulates, its total steryl ferulate content being 119 mg/100 g, whereas no measurable amounts of steryl ferulates were measured in oat bran or pearling dust of barley. The results indicated that rye and wheat and especially their bran fractions are comparable to corn as steryl ferulate sources.     

The effect of in vitro digestion on steryl ferulates from rice (Oryza sativa L.) and other grains

Polished and cargo rice, wild rice, rice bran, corn bran, and wheat bran were subjected to a static in vitro digestion model, to monitor changes in their steryl ferulate content and composition. Free sterols, possible hydrolysis products of steryl ferulates, were also measured. Additionally, steryl ferulate bioaccessibility was calculated as the percentage of steryl ferulates liberated from the grain matrix into the digestive juice. Steryl ferulate content ranged between 6.1 and 3900 μg/g and decreased by 1-63% due to digestion. A parallel increase in free sterols of more than 70% was observed in all samples. Additionally, bioaccessibility of steryl ferulates was found to be almost negligible. These findings suggest that intestinal enzymes immediately hydrolyze steryl ferulates, which are liberated from the grain matrix, and thus they are practically unavailable for absorption in the small intestine. This further indicates that the hydrolysis products of steryl ferulates could be bioactive in the gut.     

Antioxidant effects of phenolic rye (Secale cereale L.) extracts, monomeric hydroxycinnamates, and ferulic acid dehydrodimers on human low-density lipoproteins

Dietary antioxidants that protect low-density lipoprotein (LDL) from oxidation may help to prevent atherosclerosis and coronary heart disease. The antioxidant activities of purified monomeric and dimeric hydroxycinnamates and of phenolic extracts from rye (whole grain, bran, and flour) were investigated using an in vitro copper-catalyzed human LDL oxidation assay. The most abundant ferulic acid dehydrodimer (diFA) found in rye, 8-O-4-diFA, was a slightly better antioxidant than ferulic acid and p-coumaric acid. The antioxidant activity of the 8-5-diFA was comparable to that of ferulic acid, but neither 5-5-diFA nor 8-5-benzofuran-diFA inhibited LDL oxidation when added at 10-40 microM. The antioxidant activity of the monomeric hydroxycinnamates decreased in the following order: caffeic acid > sinapic acid > ferulic acid > p-coumaric acid. The antioxidant activity of rye extracts was significantly correlated with their total content of monomeric and dimeric hydroxycinnamates, and the rye bran extract was the most potent. The data suggest that especially rye bran provides a source of dietary phenolic antioxidants that may have potential health effects.     

Effects of processing on availability of total plant sterols, steryl ferulates and steryl glycosides from wheat and rye bran

Rye and wheat bran are excellent natural sources of plant sterols in the diet. Their content, however, may vary according to processing. Thermal (roasting and heating in a microwave oven), mechanical (milling and cryogenic grinding), and enzymatic treatments (hydrolysis with xylanase or beta-glucanase or a mixture of these two enzymes) were performed, and their effect on sterol content, extractability of sterols and the characteristic steryl conjugates of cereals (steryl ferulates, steryl glycosides, and acylated steryl glycosides) were studied. Mechanical and enzymatic treatments increased the apparent sterol content, whereas aqueous processing without enzymes hindered the availability of total sterols, especially from rye bran. Changes were also seen in the amounts of steryl conjugates caused by the enzymatic treatments. On the basis of the results of this study, it can be speculated that a combination of fine particle size and enzymatic processing results in optimal sterol availability in cereal processing.     

Content of gamma-oryzanol and composition of steryl ferulates in brown rice (Oryza sativa L.) of European origin

The content of gamma-oryzanol and the composition of steryl ferulates were determined in brown rice of European origin using on-line coupled liquid chromatography-gas chromatography (LC-GC). Analysis of 30 brown rice samples of various cultivars, grown at different sites and in different seasons, revealed the gamma-oryzanol content to range from 26 to 63 mg/100 g. Cycloartenyl ferulate and 24-methylenecycloartanyl ferulate were the major components of gamma-oryzanol followed by campesteryl ferulate, campestanyl ferulate, and beta-sitosteryl ferulate. The proportions of individual steryl ferulates exhibited enormous variability. However, irrespectively of the great variations observed for single steryl ferulates, the proportions of the sum of 4,4'-dimethylsteryl ferulates (cycloartenyl ferulate, 24-methylenecycloartanyl ferulate) and the sum of 4-desmethylsteryl ferulates (campesteryl ferulate, campestanyl ferulate, and beta-sitosteryl ferulate) were rather constant. The significant natural variability observed for gamma-oryzanol content and composition of steryl ferulates were shown to be influenced by environmental conditions but not by the degree of maturity of rice grains.     

Antioxidant mechanism studies on ferulic acid: identification of oxidative coupling products from methyl ferulate and linoleate

In our studies of the chain-breaking antioxidant mechanism of natural phenols in food components, ferulic acid, a phenolic acid widely distributed in edible plants, especially grain, was investigated. The radical oxidation reaction of a large amount of ethyl linoleate in the presence of the methyl ester of ferulic acid produced four types of peroxides as radical termination products. The isolation and structure determination of the peroxides revealed that they had tricyclic structures which consisted of ethyl linoleate, methyl ferulate, and molecular oxygen. Based on the formation pathway of the products, a radical scavenging reaction occurred at the 3'-position of the ferulate radical with the four types of peroxyl radicals of ethyl linoleate. The produced peroxides subsequently underwent intramolecular Diels-Alder reaction to afford stable tricyclic peroxides.     

Antioxidant activity of anthocyanins and their aglycons

The antioxidant activity of the six common anthocyanidins, pelargonidin, cyanidin, delphinidin, peonidin, petunidin, and malvidin, and their glycosidic forms was evaluated in three lipid-containing models [human low-density lipoprotein (LDL) and bulk and emulsified methyl linoleate]. In addition, the radical scavenging activity of the compounds against the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical was studied. Most anthocyanins and their aglycons acted as strong antioxidants in emulsion and LDL. Many compounds showed an activity comparable to the well-known antioxidants alpha-tocopherol, Trolox, catechin, and quercetin. In bulk methyl linoleate, anthocyanins and anthocyanidins possessed only a weak antioxidant activity or even oxidation-promoting activity. Depending on the anthocyanidin, different glycosylation patterns either enhanced or diminished the antioxidant power. For the most part, the activities of the glycosides and the aglycons did not differ remarkably in emulsion. In LDL the aglycons showed in general higher activities than the glycosides. In bulk oil, to the contrary, the glycosides were more effective than the aglycons.     

Antioxidant contents and antioxidative properties of traditional rye breads

The purpose of this research was to find out the effect of flour extraction rate on the antioxidative properties of traditional rye bread and then to compare the bioactive compounds content and antioxidant properties of rye breads with commercial wheat roll. Four types of rye flour with different extraction rates of 100 (whole meal dark flour), 95 (brown flour), 90 (brown flour), and 70% (light flour) originated from Warko rye cultivar were used for traditional bread baking with sourdough fermentation. Four types of the respective rye breads were analyzed for their potentially beneficial components, including tocopherols and tocotrienols, total phenolics and flavonoids, reduced glutathione, and inositol hexaphosphates. Moreover, the phenolic acids profile was provided. The Trolox equivalent antioxidant capacity (TEAC) of the breads was evaluated using free radical scavenging activities of 80% methanol extracts against ABTS*+ radical cation (ABTS radical cation decolorization method) whereas radical scavenging activity (RSA) was determined against 2,2-diphenyl-1-picrylhydrazyl radical (DPPH*). The superoxide dismutase-like activity (SOD-like activity) was evaluated as free radical scavenging activities of PBS extracts against superoxide anion radicals (O2*-). The results were compared to whole meal rye bread as well as to wheat roll taken as representative example of wheat based bakery product. The studies showed that flour extraction rates strongly affected the content of bioactive compounds and antioxidative properties of traditionally baked rye breads. The incorporation of the rye flours with extraction rates from 100 down to 70% in the formulation caused decrease in tocopherol (T), tocotrienol (T3), inositol hexaphosphate (IP6), and phenolic compound (TPC) contents in rye breads. No changes in reduced glutathione (GSH) contents were noted between each type of rye bread. A significant decrease in Trolox equivalent antioxidant capacity and radical DDPH scavenging activity was also found in bread formulated on flour with an extraction rate of 70% in comparison to the breads formulated on flour with extraction rates from 100 to 90%. The highest SOD-like activity was noted for rye bread formulated on flour with an extraction rate of 70%. The four types of rye breads showed better antioxidative properties and higher antioxidant contents when compared to wheat roll with one exception made to tocopherols and tocotrienols.     

Antioxidant constituents of almond [Prunus dulcis (Mill.) D.A. Webb] hulls

Almond hulls (Nonpareil variety) were extracted with methanol and analyzed by reversed phase HPLC with diode array detection. The extract contained 5-O-caffeoylquinic acid (chlorogenic acid), 4-O-caffeoylquinic acid (cryptochlorogenic acid), and 3-O-caffeoylquinic acid (neochlorogenic acid) in the ratio 79.5:14.8:5.7. The chlorogenic acid concentration of almond hulls was 42.52 +/- 4.50 mg/100 g of fresh weight (n = 4; moisture content = 11.39%). Extracts were tested for their ability to inhibit the oxidation of methyl linoleate at 40 degrees C. At an equivalent concentration (10 microg/1 g of methyl linoleate) almond hull extracts had higher antioxidant activity than alpha-tocopherol. At higher concentrations (50 microg/1 g of methyl linoleate) almond hull extracts showed increased antioxidant activity that was similar to chlorogenic acid and morin [2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-1-benzopyran-4-one] standards (at the same concentrations). These data indicate that almond hulls are a potential source of these dietary antioxidants. The sterols (3beta,22E)-stigmasta-5,22-dien-3-ol (stigmasterol) and (3beta)-stigmast-5-en-3-ol (beta-sitosterol) (18.9 mg and 16.0 mg/100 g of almond hull, respectively) were identified by GC-MS of the silylated almond hull extract.     

Antioxidant activity of isolated ellagitannins from red raspberries and cloudberries

Ellagitannins from red raspberries (Rubus idaeus) and cloudberries (Rubus chamaemorus) were isolated by using column chromatography and preparative HPLC. The berry phenolic isolates consisted of 80% (cloudberry) and of 60% (raspberry) of ellagitannins, with raspberries also containing anthocyanins. The main ellagitannins of both raspberries and cloudberries were identified by ESI-MS to consist of the dimeric sanguiin H-6 and the trimeric lambertianin C. Monomeric ellagitannins such as casuarictin in raspberries and pedunculagin in cloudberries were also found. The antioxidant activity of the berry phenolic isolate, ellagitannin isolate (mixture), ellagitannin main fraction (dimer and trimer), and ellagic acid was studied in bulk and emulsified methyl linoleate, in human low-density lipoprotein in vitro, and the radical scavenging activity was studied in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) test. Cloudberry and red raspberry ellagitannins were highly effective as radical scavengers. Berry ellagitannins also showed significant antioxidant activity toward oxidation of both human LDL and methyl linoleate emulsions. However, only weak or moderate antioxidant activity was exhibited by ellagitannins toward oxidation of bulk oil. Thus, ellagitannins contribute significantly to the antioxidant capacity of cloudberries and red raspberries in lipoprotein and lipid emulsion environments, the latter being more relevant for food applications.     

Comparison of Swiss red wheat grain and fractions for their antioxidant properties

Swiss red wheat grain, bran, aleurone, and micronized aleurone were examined and compared for their free radical scavenging properties against 2,2-diphenyl-1-picrylhydrazyl radical (DPPH*), radical cation ABTS*+ and peroxide radical anion O(2)*-, oxygen radical absorbance capacity (ORAC), chelating capacity, total phenolic content (TPC), and phenolic acid composition. The results showed that micronized aleurone, aleurone, bran, and grain may significantly differ in their antioxidant properties, TPC, and phenolic acid composition. Micronized aleurone had the greatest antioxidant activities, TPC, and concentrations of all identified phenolic acids, suggesting the potential of postharvesting treatment on antioxidant activities and availability of TPC and phenolic acids. Ferulic acid was the predominant phenolic acid in Swiss red wheat and accounted for approximately 57-77% of total phenolic acids on a weight basis. Ferulic acid concentration was well correlated with scavenging activities against radical cation and superoxide anion, TPC, and other phenolic acid concentrations, suggesting the potential use of ferulic acid as a marker of wheat antioxidants. In addition, 50% acetone and ethanol were compared for their effects on wheat ORAC values. The ORAC value of 50% acetone extracts was 3-20-fold greater than that of the ethanol extracts, indicating that 50% acetone may be a better solvent system for monitoring antioxidant properties of wheat. These data suggest the possibility to improve the antioxidant release from wheat-based food ingredients through postharvesting treatment or processing.     

Esterase activity able to hydrolyze dietary antioxidant hydroxycinnamates is distributed along the intestine of mammals.

Hydroxycinnamic acids are effective antioxidants and are abundant components of plant cell walls, especially in cereal bran. For example, wheat and rye brans are rich sources of the hydroxycinnamates ferulic acid, sinapic acid, and p-coumaric acid. These phenolics are part of human and animal diets and may contribute to the beneficial effects derived from consumption of cereal bran. However, these compounds are ester linked to the main polymers in the plant cell wall and cannot be absorbed in this complex form. The present work shows that esterases with activity toward esters of the major dietary hydroxycinnamates are distributed throughout the intestinal tract of mammals. In rats, the cinnamoyl esterase activity in the small intestine is derived mainly from the mucosa, whereas in the large intestine the esterase activity was found predominantly in the luminal microflora. Mucosa cell-free extracts obtained from human duodenum, jejunum, and ileum efficiently hydrolyzed various hydroxycinnamoyl esters, providing the first evidence of human cinnamoyl esterase(s). This study first demonstrates the release by human colonic esterase(s) (mostly of microbial origin) of sinapic acid and p-coumaric acid from rye and wheat brans. Hydrolysis by intestinal esterase(s) is very likely the major route for release of antioxidant hydroxycinnamic acids in vivo.     

Isolation and structure determination of new antioxidative ferulic acid glucoside esters from the rhizome of Alpinia speciosa, a Zingiberaceae plant used in Okinawan food culture

An assay-guided isolation gave three antioxidants including two newly identified compounds from the rhizomes of Alpinia speciosa, which is used as an important plant in the food culture of the Okinawa area of Japan. Spectroscopic analysis of the two new compounds revealed them to be new glucoside esters of ferulic acid. The antioxidant activity of the esters was measured using two different methods. Both compounds showed greater activity than that of Trolox in the TLC method; however, one of the compounds showed weaker inhibitory activity than that of Trolox and epicatechin against AMVN-induced methyl linoleate oxidation.     

Antioxidant activity and total phenolics in selected cereal grains and their different morphological fractions

The purpose of this study was to examine the antioxidant properties of water and 80% methanolic extracts of cereal grains and their different morphological fractions. Wheat (Triticum aestivum L.) cv. Almari and cv. Henika, barley (Hordeum vulgare L.) cv. Gregor and cv. Mobek, rye (Secale cereale L.) cv. Dańkowskie Zlote, oat (Avena sativa L.) cv. Slawko and buckwheat (Fagopyrum esculentum Moench) cv. Kora were used. PC (L-alpha-phosphatidylcholine) liposome system and spectrophotometric assay of total antioxidant activity (TAA) were used to evaluate the antioxidative activity of extracts. Among the water extracts, only the one prepared from buckwheat exhibited antioxidant activity at the concentration analyzed. The following hierarchy of antioxidant activity was provided for 80% methanolic extracts originated from whole grain: buckwheat > barley > oat > wheat congruent with rye. The antioxidant activity was observed in extract prepared from separated parts of buckwheat and barley. In respect to hulls, the antioxidant hierarchy was as follows: buckwheat > oat > barley. The correlation coefficient between total phenolic compounds and total antioxidative activity of the extracts was -0.35 for water extracts and 0.96, 0.99, 0.80, and 0.99 for 80% methanolic extracts originated from whole grains, hulls, pericarb with testa fractions and endosperm with embryo fractions, respectively.     

Rapid peroxyl radical scavenging capacity (PSC) assay for assessing both hydrophilic and lipophilic antioxidants

This paper reports a simple, rapid, and sensitive assay for assessing peroxyl radical scavenging capacity (PSC) of both hydrophilic and lipophilic antioxidant compounds and food extracts. The assay is based on the degree of inhibition of dichlorofluorescin oxidation by antioxidants that scavenge peroxyl radicals, generated from thermal degradation of 2,2'-azobis(amidinopropane). For hydrophilic antioxidant activity, the dose required to cause a 50% inhibition of the reaction (EC(50)) ranged from 2.41 +/- 0.02 (EGCG) to 21.26 +/- 0.38 microM (ferulic acid). EC(50) values for the hydrophilic antioxidant activity of food extracts ranged from 309.2 +/- 3.63 (apple) to 3345.1 +/- 151.5 micromol of vitamin C equiv/100 g for wheat bran. The EC(50) values for lipophilic antioxidant activity were 1.58 +/- 0.11 (Trolox), 4.35 +/- 0.43 (alpha-tocopherol), 18.94 +/- 0.38 (BHA), and 182.69 +/- 13.7 microM (BHT). Whole grain lipophilic antioxidant activity ranged from 3.49 +/- 0.57 (wheat) to 8.79 +/- 1.98 micromol of alpha-tocopherol equiv/100 g of rice. Hydrophilic antioxidant activity contributed >98% of the total antioxidant activity (hydrophilic plus lipophilic) of whole grains tested. The PSC assay was accurate (86-108% recovery), precise (0.12-11% CV), and reproducible (12% RSD) and produced results comparable to those of similar published assays. The PSC assay can be routinely used to analyze or screen both hydrophilic and lipophilic antioxidants or food extracts and will be a valuable alternative biomarker for future epidemiological studies of chronic diseases.     

Total phenolics and antioxidant activities of fenugreek, green tea, black tea, grape seed, ginger, rosemary, gotu kola, and ginkgo extracts, vitamin E, and tert-butylhydroquinone

The total phenolics and antioxidant activities of fenugreek, green tea, black tea, grape seed, ginger, rosemary, gotu kola, and ginkgo extracts, vitamin E, and tert-butylhydroquinone, were determined. Grape seed and green tea were analyzed for their phenolic constituents using high-performance liquid chromatography. The total phenolics of the plant extracts, determined by the Folin-Ciocalteu method, ranged from 24.8 to 92.5 mg of chlorogenic acid equivalent/g dry material. The antioxidant activities of methanolic extracts determined by conjugated diene measurement of methyl linoleate were 3.4-86.3%. The antioxidant activity of the extracts using chicken fat by an oxidative stability instrument (4.6-10.2 h of induction time) followed a similar trend in antioxidant activity as determined by the Folin-Ciocalteu method. Seven phenolics in grape seed and green tea extracts were identified that ranged from 15.38 to 1158.49 and 18.3 to 1087.02 mg/100 g of extract, respectively. Plant extracts such as green tea and grape seed extracts can be used to retard lipid oxidation in a variety of food products.     

Contents of phenolic acids, alkyl- and alkenylresorcinols, and avenanthramides in commercial grain products

The contents of free and total phenolic acids and alk(en)ylresorcinols were analyzed in commercial products of eight grains: oat (Avena sativa), wheat (Triticum spp.), rye (Secale cerale), barley (Hordeum vulgare), buckwheat (Fagopyrum esculentum), millet (Panicum miliaceum), rice (Oryza sativa), and corn (Zea mays). Avenanthramides were determined in three oat products. Free phenolic acids, alk(en)ylresorcinols, and avenanthramides were extracted with methanolic acetic acid, 100% methanol, and 80% methanol, respectively, and quantified by HPLC. The contents of total phenolic acids were quantified by HPLC analysis after alkaline and acid hydrolyses. The highest contents of total phenolic acids were in brans of wheat (4527 mg/kg) and rye (4190 mg/kg) and in whole-grain flours of these grains (1342 and 1366 mg/kg, respectively). In other products, the contents varied from 111 mg/kg (white wheat bread) to 765 mg/kg (whole-grain rye bread). Common phenolic acids found in the grain products were ferulic acid (most abundant), ferulic acid dehydrodimers, sinapic acid, and p-coumaric acid. The grain products were found to contain either none or only low amounts of free phenolic acids. The content of avenanthramides in oat flakes (26-27 mg/kg) was about double that found in oat bran (13 mg/kg). The highest contents of alk(en)ylresorcinols were observed in brans of rye (4108 mg/kg) and wheat (3225 mg/kg). In addition, whole-grain rye products (rye bread, rye flour, and whole-wheat flour) contained considerable levels of alk(en)ylresorcinols (524, 927, and 759 mg/kg, respectively).     

Carotenoid, tocopherol, phenolic acid, and antioxidant properties of Maryland-grown soft wheat

Consumers' desires to either reduce the risk of or manage a specific health condition through improved diet have stimulated the research of agricultural products for their potential health beneficial components such as tocopherols and natural antioxidants. Soft wheat is one of the major crops in Maryland, with little information available about its potentially beneficial components. This study examined eight selected Maryland-grown soft wheat varieties or experimental lines for their potential beneficial components including tocopherols, carotenoids, total phenolics and phenolic acids and their antioxidant properties, including Fe(2+) chelating capacity and free radical scavenging activities against 2,2-diphenyl-1-picrylhydrazyl radical (DPPH(*) ), radical cation ABTS(*)(+), and oxygen radical (ORAC). The results showed that all tested soft wheat grain samples contained alpha-tocopherol, with a range of 3.4-10.1 microg/g. Lutein was the primary carotenoid present in the grain samples at a level of 0.82-1.14 microg/g, along with significant amounts of zeaxanthin and beta-carotene. Vanillic, syringic, p-coumaric, and ferulic acids were found in soluble free, soluble conjugated, and insoluble bound forms in the grain extracts, with ferulic acid as the predominant phenolic acid. The eight soft wheat varieties differed in their antioxidant properties. The tested wheat grain samples exhibited ED(50) values against DPPH(*) of 23-27 mg of grain equiv/mL, ORAC of 32.9-48 micromol of Trolox equiv (TE)/g, and ABTS(*)(+) scavenging capacity of 14.3-17.6 micromol of TE/g. These data suggest the possibility of producing soft wheat varieties rich in selected health beneficial factors for optimum human nutrition though breeding programs.     

Antioxidant activity of grains

Epidemiological studies have shown that consumption of whole grains and grain-based products is associated with reduced risk of chronic diseases. The health benefits of whole grains are attributed in part to their unique phytochemical composition. However, the phytochemical contents in grains have been commonly underestimated in the literature, because bound phytochemicals were not included. This study was designed to investigate the complete phytochemical profiles in free, soluble conjugated, and insoluble bound forms, as well as their antioxidant activities in uncooked whole grains. Corn had the highest total phenolic content (15.55 +/- 0.60 micromol of gallic acid equiv/g of grain) of the grains tested, followed by wheat (7.99 +/- 0.39 micromol of gallic acid equiv/g of grain), oats (6.53 +/- 0.19 micromol of gallic acid equiv/g of grain), and rice (5.56 +/- 0.17 micromol of gallic acid equiv/g of grain). The major portion of phenolics in grains existed in the bound form (85% in corn, 75% in oats and wheat, and 62% in rice), although free phenolics were frequently reported in the literature. Ferulic acid was the major phenolic compound in grains tested, with free, soluble-conjugated, and bound ferulic acids present in the ratio 0.1:1:100. Corn had the highest total antioxidant activity (181.42 +/- 0.86 micromol of vitamin C equiv/g of grain), followed by wheat (76.70 +/- 1.38 micromol of vitamin C equiv/g of grain), oats (74.67 +/- 1.49 micromol of vitamin C equiv/g of grain), and rice (55.77 +/- 1.62 micromol of vitamin C equiv/g of grain). Bound phytochemicals were the major contributors to the total antioxidant activity: 90% in wheat, 87% in corn, 71% in rice, and 58% in oats. Bound phytochemicals could survive stomach and intestinal digestion to reach the colon. This may partly explain the mechanism of grain consumption in the prevention of colon cancer, other digestive cancers, breast cancer, and prostate cancer, which is supported by epidemiological studies.