Bound phenolics in foods, a review

Research has shown that whole grain consumption helps lower the risk of cardiovascular disease, ischemic stroke, type II diabetes, metabolic syndrome, and gastrointestinal cancers (36,37). In addition to dietary fiber, whole grains contain many health-promoting components such as vitamins, minerals, and phytochemicals, which include phenolic compounds. Phenolic compounds have antioxidant properties and can protect against degenerative diseases (i.e., heart disease and cancer) in which reactive oxygen species (i.e., superoxide anion, hydroxyl radicals, and peroxy radicals) are involved (32,57). The general definition of a phenolic compound is any compound containing a benzene ring with one or more hydroxyl groups. Phenolic acids, flavonoids, condensed tannins, coumarins, and alkylresorcinols are examples. All plant-based foods have phenols, which affect their appearance, taste, odor, and oxidative stability (45). In cereal grains, these compounds are located mainly in the pericarp, and they can be concentrated by decorticating the grain to produce bran, which can be incorporated into a food product (i.e., breads, cookies, and tortillas) with increased dietary fiber levels and nutraceutical properties. Most of the literature on plant phenolics focuses mainly on those in fruits, vegetables, wines, and teas (33,50,53,58, 74). However, many phenolic compounds in fruits and vegetables (i.e., phenolic acids and flavonoids) are also reported in cereals. The different species of grains have a great deal of diversity in their germplasm resources, which can be exploited. Some phenols are unique to one plant species, such as the oat avenanthramides (12). Different methods of analysis for phenols and antioxidant activity are reported in the literature. Unfortunately, it is difficult to make comparisons of phenol and antioxidant activity levels in cereals since different methods have been used. The purpose of this article is to give an overview of phenolic compounds reported in whole grain cereals and to compare their phenol and antioxidant activity levels.

Phenolic compounds in cereal grains and their health benefits

Epidemiological studies suggested that the low incidence of certain chronic diseases in rice-consuming regions of the world might be associated with the antioxidant compound contents of rice. The molecules with antioxidant activity contained in rice include phenolic acids, flavonoids, anthocyanins, proanthocyanidins, tocopherols, tocotrienols, γ-oryzanol, and phytic acid. This review provides information on the contents of these compounds in rice using a food composition database built from compiling data from 316 papers. The database provides access to information that would have otherwise remained hidden in the literature. For example, among the four types of rice ranked by color, black rice varieties emerged as those exhibiting the highest antioxidant activities, followed by purple, red, and brown rice varieties. Furthermore, insoluble compounds appear to constitute the major fraction of phenolic acids and proanthocyanidins in rice, but not of flavonoids and anthocyanins. It is clear that to maximize the intake of antioxidant compounds, rice should be preferentially consumed in the form of bran or as whole grain. With respect to breeding, japonica rice varieties were found to be richer in antioxidant compounds compared with indica rice varieties. Overall, rice grain fractions appear to be rich sources of antioxidant compounds. However, on a whole grain basis and with the exception of γ-oryzanol and anthocyanins, the contents of antioxidants in other cereals appear to be higher than those in rice.

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Rice antioxidants: phenolic acids, flavonoids, anthocyanins, proanthocyanidins, tocopherols, tocotrienols, γ-oryzanol, and phytic acid

Antioxidant activity of methanolic extracts from some grains consumed in Korea

Increased consumption of whole grains has been associated with reduced risk of developing major chronic diseases. These health benefits have been attributed in part to their unique phytochemicals. Previous studies on black rice mainly focused on anthocyanins. Little is known about the phytochemical profiles and antioxidant activities of different black rice varieties. The objective of this study was to determine the phytochemical profiles and antioxidant activity of rice bran samples from 12 diverse varieties of black rice. The free, bound, and total phenolic contents of black rice bran samples ranged from 2086 to 7043, from 221.2 to 382.7, and from 2365 to 7367 mg of gallic acid equiv/100 g of dry weight (DW), respectively. The percentage contribution of free phenolics to the total ranged from 88.2 to 95.6%. The average values of free, bound, and total phenolic contents of black rice bran were 8, 1.5, and 6 times higher than those of white rice bran, respectively (p < 0.05). The free, bound, and total fl...

Phenolic Profiles and Antioxidant Activity of Black Rice Bran of Different Commercially Available Varieties

Two hydroxycinnamate sucrose esters, 6‘-O-(E)-feruloylsucrose and 6‘-O-(E)-sinapoylsucrose, were isolated from methanol extracts of rice bran. Soluble and insoluble phenolic compounds as well as 6‘-O-(E)-feruloylsucrose and 6‘-O-(E)-sinapoylsucrose from white rice, brown rice, and germinated brown rice were analyzed using HPLC. The results demonstrated that the content of insoluble phenolic compounds was significantly higher than that of soluble phenolics in rice, whereas almost all compounds identified in germinated brown rice and brown rice were more abundant than those in white rice. 6‘-O-(E)-Feruloylsucrose (1.09 mg/100 g of flour) and 6‘-O-(E)-sinapoylsucrose (0.41 mg/100 g of flour) were found to be the major soluble phenolic compounds in brown rice. During germination, an ∼70% decrease was observed in the content of the two hydroxycinnamate sucrose esters, whereas free phenolic acid content increased significantly; the ferulic acid content of brown rice (0.32 mg/100 g of flour) increased to 0.48 mg...

Analysis of phenolic compounds in white rice, brown rice, and germinated brown rice.

High-performance liquid chromatographic determination of phenolic compounds in rice

Hawthorn polyphenol (HP) was prepared by ethyl acetate treatment of the ethanol extract (HE) of Chinese hawthorn fruit. The concentrations of 15 polyphenols in the HP, HE, extraction residue (HJ), and a hawthorn leaf extract (HF) were determined by HPLC. For HP, the total content of the 15 polyphenols was 21.4%, comprised of 19.7% of procyanidins, 1.21% of chlorogenic acid, and 0.48% of flavonoids, compared to 2.55% for the HE. The yields of procyanidin monomer, dimer, trimer, tetramer, and pentamer were 50.5%, 30.3%, 23.0%, 14.6%, and 12.5% respectively, and the mean degree of polymerization was reduced to 1.39 (HP) from 1.65 (HE). Seven different physiological actions of the four extracts were investigated. The HP showed strong O(2)(-) and (.-)OH scavenging capacities (IC(50) values of 6.3 microg/ml and 1.1 microg/ml respectively), as well as selective prolyl endopeptidase inhibition (IC(50) of 60 microg/ml). The active constituents appeared to be procyanidins.

https://www.tandfonline.com/doi/pdf/10.1271/bbb.60361

Polyphenolic Content and Physiological Activities of Chinese Hawthorn Extracts

Antihypertensive effects of orally administered eggplant (Solanum melongena) rich in acetylcholine on spontaneously hypertensive rats

Choline is an essential nutrient and choline esters are potential functional food ingredients. We aimed to analyze the choline compound content in 19 cultivated fruits and vegetables and identify those with high acetylcholine content. We utilized liquid chromatography with tandem mass spectrometry to quantify choline compounds according to the standard addition method. Choline compounds were extracted from lyophilized fruit/vegetable powders and passed through a weakly acidic cation exchange column, resulting in a concentrated solution of choline compounds. The compounds were separated on a pentafluorophenyl column and then analyzed using positive mode electrospray ionization. Results showed that acetylcholine and choline were the primary choline compounds in all agricultural products; propionylcholine and butyrylcholine were minor compounds in 17 and 12 agricultural products, respectively. The acetylcholine concentration was 2900-fold higher in eggplants (6.12 mg/100 g fresh weight [FW]) than in other agricultural products (average: 2.11 × 10-3 mg/100 g FW). The concentration of acetylcholine differed only 2-fold between eggplant cultivars with the highest ('Higomurasaki': 5.53 mg/100 g FW) and lowest ('Onaga nasu': 2.79 mg/100 g FW) concentrations. The half-life of acetylcholine in eggplants was approximately 16 days, which is longer the shelf life of eggplants. Thus, eggplants can be a good source of acetylcholine.

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Su Tian

Papers

Analysis of phenolic compounds in white rice, brown rice, and germinated brown rice.

High-performance liquid chromatographic determination of phenolic compounds in rice

Polyphenolic Content and Physiological Activities of Chinese Hawthorn Extracts

Antihypertensive effects of orally administered eggplant (Solanum melongena) rich in acetylcholine on spontaneously hypertensive rats

LC-MS/MS Analysis of Choline Compounds in Japanese-Cultivated Vegetables and Fruits.