Concentrations of oligomers and polymers of proanthocyanidins in red and purple rice bran and their relationships to total phenolics, flavonoids, antioxidant capacity and whole grain color

Rice Bran Extraction and Stabilization Methods for Nutrient and Phytochemical Biofortification, Nutraceutical Development, and Dietary Supplementation

Rice is a global staple food crop for nearly half of the world's population. Rice bran along with the germ are essential components of whole-grain rice and have immense potential for enhancing human nutrition. Rice bran has a unique composition and distinct requirements for processing before it can be consumed by humans when compared with other cereal brans. The comprehensive overview and synthesis of rice bran processing include extending the shelf life for functional food product development and extraction of bioactive components. This narrative review highlights established and innovative stabilization approaches, including solvent extraction and enzymatic treatments, which are critical methods and technologies for wider rice bran availability. The nutrient and phytochemical profiles of rice bran may improve with new cultivar development and food-fortification strategies. The postharvest agricultural practices and processing techniques can reduce food waste while also supporting growers to produce novel pigmented cultivars that can enhance nutritional value for human health.

Advances and Future Prospects of Pigment Deposition in Pigmented Rice

Pigmented rice, particularly the black and red varieties, is popular due to its better nutritional value. Anthocyanins and proanthocyanidins are two major flavonoid subcategories with broad physiological functions and therapeutic significance. However, pigment deposition is a complex process, and the molecular mechanism involved remains unknown. This review explores the metabolites responsible for the pigmentation in various rice tissues. Moreover, the current challenges, feasible strategies, and potential future directions in pigmented rice research are reported.

Comparative study for metabolomics, antioxidant activity, and molecular docking simulation of the newly bred Korean red rice accessions

This study analyzed the metabolite profiles and antioxidant capacities of two waxy and non-waxy Korean red rice accessions newly bred. Fifteen phenolic compounds were detected in the rice samples. Accession1 had high fatty acids, phytosterols, and vitamin E; accession3 had high vitamin E and phytosterol; and accession4 had a high total flavonoid. The correlation analysis findings from this study validated the positive association between all the metabolites and antioxidant activity. in silico results revealed that protocatechuic acid had a docking score of -9.541, followed by luteolin, quercetin, and caffeic acid, all of which had significant docking scores and a significant number of contacts. Similarly, molecular dynamics simulations showed that phytochemicals had root mean square deviation values of <2.8 Å with Keap 1, indicating better stability. This study provides valuable insights into potential directions for future investigations and improvements in the functional qualities of other colored rice varieties.

Association of flavonoid intake with coronary artery disease risk in the older population based on the National Health and Nutrition Examination Survey

We investigated the association between flavonoid intake and coronary artery disease (CAD) risk in older adults. Data were extracted from the National Health and Nutrition Examination Survey (age ≥ 70 years; 2007-2010 and 2017-2018; n = 2 417). The total flavonoid and flavonoid subclass intake was calculated using validated food frequency questionnaires. The association between flavonoid intake and CAD risk was examined using generalized linear models with restricted cubic spline models. After multivariate adjustment, anthocyanin intake was positively associated with CAD risk; no significant associations were observed between other flavonoid subcategories and endpoint outcomes. Anthocyanins exhibited a non-linear association with CAD risk, and threshold effect analysis showed an inflection point of 15.8 mg/day for anthocyanins. Per unit increase in anthocyanins, the odds of CAD on the left of the inflection point decreased by 2%, while the odds on the right increased by 35.8%. Excessive flavonoid intake may increase CAD risk in the older population.

Health-promoting germinated rice and value-added foods: a comprehensive and systematic review of germination effects on brown rice

Over the last 30 years, thousands of articles have appeared examining the effects of soaking and germinating brown rice (BR). Variable germination conditions and methods have been employed to measure different health-beneficial parameters in a diverse germplasm of BR. Research results may therefore appear inconsistent with occasional anomalies, and it may be difficult to reach consensus concerning expected trends. Herein, we amassed a comprehensive review on germinated brown rice (GBR), attempting to codify 133 peer-reviewed articles regarding the effects on 164 chemical parameters related to health and nutrition in BR and in value-added food products. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA-2020) approach was used to direct the flow of the literature search. A pair-wise comparison t-test was performed to deliver an overall approach indicating when a given compound has been found to significantly increase or decrease through germination, which was grouped into GABA and polyamines, γ-Oryzanol and phytosterols, phenolic compounds, vitamins, proteins and amino acids, starchy carbohydrates, free sugars, lipids, minerals and phytic acid. This resource will stimulate interest in germinating rice and optimistically help increase both production and consumption of highly nutritious, health-beneficial rice with pigmented bran.

Active compounds: A new direction for rice value addition

The development of rice active compounds is conducive to improving the added value of rice. This paper focused on the types and effects of active compounds in rice. Furthermore, it summarized the effect of rice storage and processing technology on rice active compounds. We conclude the following: Rice contains a large number of active compounds that are beneficial to humans. At present, the research on the action mechanism of rice active compounds on the human body is not deep enough, and the ability to deeply process rice is insufficient, greatly limiting the development of the rice active compound industry. To maximize the added value of rice, it is necessary to establish a dedicated preservation and processing technology system based on the physicochemical properties of the required active compounds. Additionally, attention should be paid to the development and application of composite technologies during the development of the rice active compound industry.

Genetic loci regulating the concentrations of anthocyanins and proanthocyanidins in the pericarps of purple and red rice

The pigmented flavonoids, anthocyanins and proanthocyanidins, have health promoting properties. Previous work determined that the genes Pb and Rc turn on and off the biosynthesis of anthocyanins (purple) and proanthocyanidins (red), respectively. Not yet known is how the concentrations of these pigmented flavonoids are regulated in grain pericarps. Quantitative trait locus (QTL) analysis in a population of rice (Oryza sativa L.) F5 recombinant inbred lines from white pericarp "IR36ae" x red+purple pericarp "242" revealed three QTLs associated with grain concentrations of anthocyanins (TAC) or proanthocyanidins (PA). Both TAC and PA independently mapped to a 1.5 Mb QTL region on chromosome 3 between RM3400 (at 15.8 Mb) and RM15123 (17.3 Mb), named qPR3. Across 2 years, qPR3 explained 36.3% of variance in TAC and 35.8% in PA variance not attributable to Pb or Rc. The qPR3 region encompasses Kala3, a MYB transcription factor previously known to regulate purple grain characteristics. Study of PbPbRcrc progeny showed that TAC of RcRc near isogenic lines (NILs) was 2.1-4.5x that of rcrc. Similarly, study of PbPbRcRc NILs, which had 70% higher PA than pbpbRcRc NILs, revealed a mutual enhancement, not a trade-off between these compounds that share precursors. This suggests that Pb and Rc upregulate genes in a shared pathway as they activate TAC and PA synthesis, respectively. This study provides molecular markers for facilitating marker-assisted selection of qPR3, qPR5, and qPR7 to enhance grain concentrations of pigmented flavonoids and documented that stacking Rc and Pb genes further increases both flavonoid compounds.

A fast breeding strategy creates fragrance- and anthocyanin-enriched rice lines by marker-free gene-editing and hybridization

As rice is a staple food for nearly half of the world's population, rice varieties with excellent agronomic traits as well as high flavor and nutritional quality such as fragrant rice and purple rice are naturally favored by the market. In the current study, we adopt a fast breeding strategy to improve the aroma and anthocyanin content in the excellent rice inbred line, F25. The strategy skillfully used the advantages of obtaining editing pure lines in T0 generation of CRISPR/Cas9 editing system and easy observation of purple character and grain shape, integrated the subsequent screening of non-transgenic lines, and the elimination of undesirable edited variants from gene-editing and cross-breeding at the same time as the separation of the progeny from the purple cross, thus expediting the breeding process. Compared with conventional breeding strategies, this strategy saves about 6-8 generations and reduces breeding costs. Firstly, we edited the OsBADH2 gene associated with rice flavor using an Agrobacterium-mediated CRISPR/Cas9 system to improve the aroma of F25. In the T0 generation, a homozygous OsBADH2-edited F25 line (F25B) containing more of the scented substance 2-AP was obtained. Then, we crossed F25B (♀) with a purple rice inbred line, P351 (♂), with high anthocyanin enrichment to improve the anthocyanin content of F25. After nearly 2.5 years of screening and identification over five generations, the undesirable variation characteristics caused by gene-editing and hybridization and the transgenic components were screened out. Finally, the improved F25 line with highly stable aroma component, 2-AP, increased anthocyanin content and no exogenous transgenic components were obtained. This study not only provides high-quality aromatic anthocyanin rice lines that meet the market demand, but also offers a reference for the comprehensive use of CRISPR/Cas9 editing technology, hybridization, and marker-assisted selection to accelerate multi-trait improvement and breeding process.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11032-023-01369-1.

Procyanidins from Cranberry Press Residues-Extraction Optimization, Purification and Characterization

Procyanidins are a polyphenolic group that can be found in a variety of foods such as chocolate, tea, cranberries and others. Type A procyanidins can be found in a handful of sources and one of the richest sources are American cranberries. These compounds possess antioxidative, anticancer and anti-inflammatory activities and are most widely used as prevention for urinary tract infections. Cranberries are utilized for jam and juice production, and the latter produces industrial food waste press residues. Press residues contain free and bound procyanidins which can be extracted for use as nutraceuticals. In this study, the extraction of cranberry press residues has been optimized using RSM and the resulting extracts have been purified and fractionated. The obtained procyanidin fractions have been investigated for their antioxidative potential and analyzed using LC-ESI-FTICR-HRMS to determine individual procyanidins. The optimization showed that the optimal extraction can be conducted using acetone in a concentration of 53% without the addition of an acidifying agent. Strong correlation was observed for procyanidin contents and their antioxidative activity using DPPH, ABTS and FRAP methods. The purified fractions contained 78 individual (65 Type A) procyanidins with the degree of polymerization of up to 9.

Effect of radiation processing on phenolic antioxidants in cereal and legume seeds: A review

Phenolic compounds in cereal and legume seeds show numerous benefits to human health mainly because of their good antioxidant capacity. However, long-term storage and some improper preservation may reduce their antioxidant potential. It is necessary to retain or modify the phenolic antioxidants with improved technology before consumption. Radiation processing is usually applied as a physical method to extend the shelf life and retain the quality of plant produce. However, the effect of radiation processing on phenolic antioxidants in cereal and legume seeds is still not well understood. This review summarizes recent research on the effect of radiation, including ionizing and nonionizing radiation on the content and profile of phenolic compounds, and antioxidant activities in cereal and legume seeds, the influencing factors and possible mechanisms are also discussed. The article will improve the understanding of radiation effect on phenolic antioxidants, and promote the radiation modification of natural phenolic compounds in cereal and legume seeds and other sources.

Development of a quantified herbal extract of hawthorn Crataegus mexicana leaves with vasodilator effect

Hawthorn (Crataegus spp.) has been used for the treatment of several heart diseases and hypertension. The studies carried out on several hawthorn species have led to the development of standardized extracts useful in the cure of mild chronic cardiac diseases.

In Mexico, the most common Crataegus species are C. mexicana and C. gracilior. Decoctions prepared from the fruits and leaves of these species have been employed to the treat respiratory diseases, tachycardia and to improve coronary blood flow. Considering that to date there are no reports of the use of Mexican Crataegus species to treat cardiovascular diseases, we propose an analytical method to obtain a quantified extract of Crataegus mexicana leaves for the development of a standardized extract with therapeutic value in cardiovascular diseases as an alternative source to the extracts obtained from Crataegus species of European and Asian origin.

Therefore, the aim of this study was to obtain an extract prepared from C. mexicana leaves with the highest vasodilator activity to select the optimal chemical marker to stablish and validate a reversed-phase high-performance liquid chromatography (RPHPLC-DAD) analytical method for obtaining a quantified extract with vasodilator effect.

The results obtained from the analytical method validation, which was carried out according to the guidelines stablished in the Eurachem Guide and the ICH guidelines proved that the RPHPLC-DAD method we developed was specific, precise, accurate, and showed good linearity over the concentration range of 3 – 21 µg/ml for (-)-epicatechin and rutin, which were selected as chemical markers.

Role of nutraceutical starch and proanthocyanidins of pigmented rice in regulating hyperglycemia: Enzyme inhibition, enhanced glucose uptake and hepatic glucose homeostasis using in vitro model

Dysregulation of glucose homeostasis result in hyperglycemia and pigmented rice, unique combination of high quality starch and phenolics has the potential in regulating it. In this study, pigmented rice was characterized in terms of nutraceutical starch (NS) and phenolic content. Further the effect of rice phenolics on carbolytic enzyme inhibition, glucose uptake, hepatic glucose homeostasis and anti-glycation ability was analyzed in vitro. The most relevant effect on enzyme inhibition (α-amylase: IC₅₀-42.34 µg/mL; α-glucosidase: IC₅₀:63.89 µg/mL), basal uptake of glucose (>39.5%) and anti-glycation ability (92%) was found in red rice (RR), than black rice (BR). The role of RR phenolics in regulating glucose homeostasis was deciphered using hepatic cell line system, which found up-regulation of glucose transporter 2 (GLUT2) and glycogen synthase 2 (GYS2); while expression of gluconeogenic genes were found down regulated. To our knowledge this study is the first report validating the role of starch-phenolic quality towards anti-hyperglycemic effect of RR.

Effects of edible plant polyphenols on gluten protein functionality and potential applications of polyphenol-gluten interactions

Expanding plant-based protein applications is increasingly popular. Polyphenol interactions with wheat gluten proteins can be exploited to create novel functional foods and food ingredients. Polyphenols are antioxidants, thus generally decrease gluten strength by reducing disulfide cross-linking. Monomeric polyphenols can be used to reduce dough mix time and improve flexibility of the gluten network, including to plasticize gluten films. However, high-molecular-weight polyphenols (tannins) cross-link gluten proteins, thereby increasing protein network density and strength. Tannin-gluten interactions can greatly increase gluten tensile strength in dough matrices, as well as batter viscosity and stability. This could be leveraged to reduce detrimental effects of healthful inclusions, like bran and fiber, to loaf breads and other wheat-based products. Further, the dual functions of tannins as an antioxidant and gluten cross-linker could help restructure gluten proteins and improve the texture of plant-based meat alternatives. Tannin-gluten interactions may also be used to reduce inflammatory effects of gluten experienced by those with gluten allergies and celiac disease. Other potential applications of tannin-gluten interactions include formation of food matrices to reduce starch digestibility; creation of novel biomaterials for edible films or medical second skin type bandages; or targeted distribution of micronutrients in the digestive tract. This review focuses on the effects of polyphenols on wheat gluten functionality and discusses emerging opportunities to employ polyphenol-gluten interactions.

The Effect of a Low GI Diet on Truncal Fat Mass and Glycated Hemoglobin in South Indians with Type 2 Diabetes-A Single Centre Randomized Prospective Study

Background: There has been no previous study that has investigated the effect of a low glycemic index (LGI) diet with local recipes of South Indian cuisine on the body fat composition using dual-energy X-ray absorptiometry (DXA). Truncal obesity has been associated with the risk of metabolic disorders and cardiovascular diseases. Aim: The aim of this study was to examine the effect of a low GI diet on glycemic control and body composition in people with type 2 diabetes in South India. Method: This was a prospective and randomized controlled study that was conducted over a period of 24 weeks. A total of 40 participants were recruited from the Department of Endocrinology and Diabetes Outpatient in Kerala, South India. All the patients had type 2 diabetes and were randomly assigned and given advice and instructions to follow either a low GI diet plan (n = 18) or their usual diet, which served as control (n = 18). The advice was reinforced throughout the study period. Dietary compliance was evaluated based on a 24 h dietary recall at weeks 3, 11, 12, 18, 23, and 24. The age of the subjects ranged from 35 to 65 years. Anthropometric, body composition, and cardio-metabolic parameters were measured according to standard procedures. T-tests were conducted to compare differences between intervention and control groups and the Pearson correlation coefficient was used to evaluate associations between the variables. Results: There were significant reductions (p < 0.05) in the low GI diet compared to the control group with respect to weight, body mass index (BMI), and triceps skinfold thickness. Similarly, significant reductions were observed in the low GI diet group with respect to region, total fat, android, and gynoid fat mass and the differences between the groups were significant at p < 0.05. There was also a positive correlation between BMI and android fat mass (r = 0.745), total fat mass (r = 0.661), total truncal mass (r = 0.821), and truncal fat (r = 0.707). There was a significant reduction in glycated hemoglobin in the low GI diet group compared to the control group at p < 0.05. Conclusion: This study has demonstrated that there was a significant reduction (p < 0.05) of truncal obesity and glycated hemoglobin in patients with type 2 diabetes on a local diet of South Indian cuisine with low GI compared with the control.

Hydrolytic rancidity and its association with phenolics in rice bran

Whole grain rice, which has the bran layer intact, contains more nutrients and health beneficial compounds than its milled rice equivalent. Its consumption is associated with a reduction in the risk of developing several chronic diseases. However, the bran contains non-starch lipids deposited along with the lipid degrading enzymes, lipase and lipoxygenase, resulting in a relatively short shelf life for whole grain rice. We studied the genotypic diversity of lipase induced hydrolytic rancidity (HR) level in the bran of 134 diverse genotypes and found more than a 15-fold variation. Among the genotypes, those with red or brown bran had lower HR than the purple, light brown and white brans. Total phenolic content and anthocyanins were negatively correlated with the HR in purple brans suggesting their inhibitory effect on lipase during bran storage. In conclusion, low HR genotypes could be used as breeding materials to improve the storage stability of whole grain rice.

Tricin levels and expression of flavonoid biosynthetic genes in developing grains of purple and brown pericarp rice

The methylated flavone tricin has been associated with numerous health benefits, including reductions in intestinal and colon cancers in animal models. Tricin is found in a wide range of plant species and in many different tissues. However, whole cereal grains, such as rice, barley, oats, and wheat, are the only food sources of tricin, which is located in the bran portion of the grain. Variation in tricin levels was found in bran from rice genotypes with light brown, brown, red, and purple pericarp color, with the purple pericarp genotypes having the highest levels of tricin. Here, we analyzed tricin and tricin derivative levels in developing pericarp and embryo samples of a purple pericarp genotype, IAC600, that had high tricin and tricin derivative levels in the bran, and a light brown pericarp genotype, Cocodrie, that had no detectable tricin or tricin derivatives in the bran. Tricin and tricin derivatives were detected in both the pericarp and embryo of IAC600 but only in the embryo of Cocodrie. The purple pericarp rice had higher total levels of free tricin plus tricin derivatives than the light brown pericarp rice. When expressed on a per grain basis, most of the tricin component of IAC600 was in the pericarp. In contrast, Cocodrie had no detectable tricin in the pericarp samples but did have detectable chrysoeriol, a precursor of tricin, in the pericarp samples. We also used RNA-Seq analysis of developing pericarp and embryo samples of the two cultivars to compare the expression of genes involved in the flavonoid biosynthetic pathway. The results presented here suggest that understanding the basis of tricin accumulation in rice pericarp may lead to an approach to increasing tricin levels in whole grain rice. From analysis of gene expression levels in the pericarp samples it appears that regulation of the flavone specific genes is independent of regulation of the anthocyanin biosynthetic genes. It therefore may be feasible to develop brown pericarp rice cultivars that accumulate tricin in the pericarp.

Extraction and Analysis of Phenolic Compounds in Rice: A Review

Rice represents the main source of calorie intake in many world countries and about 60% of the world population include rice in their staple diet. Whole grain rice, also called brown rice, represent the unpolished version of the more common white rice including bran, germ, and endosperm. Many health-promoting properties have been associated to the consumption of whole grain rice and, for this reason, great attention has been paid by the scientific community towards the identification and the quantification of bioactive compounds in this food item. In this contribution, the last five years progresses in the quali-quantitative determination of phenolic compounds in rice have been highlighted. Special attention has been devoted to the most recent strategies for the extraction of the target compounds from rice along with the analytical approaches adopted for the separation, identification and quantification of phenolic acids, flavonoids, anthocyanins, and proanthocyanidins. More specifically, the main features of the “traditional” extraction methods (i.e., maceration, ultrasound-assisted extraction) have been described, as well as the more innovative protocols involving advanced extraction techniques, such as MAE (microwave-assisted extraction). The predominant role of HPLC in the definition of the phenolic profile has been examined also presenting the most recent results obtained by using mass spectrometry-based detection systems. In addition, the most common procedures aimed to the quantification of the total amount of the cited classes of phenolic compounds have been described together with the spectrophotometric protocols aimed to the evaluation of the antioxidant properties of rice phenolic extracts (i.e., FRAP, DPPH, ABTS and ORAC).

Physicochemical properties of germinated dehulled rice flour and energy requirement in germination as affected by ultrasound treatment

Limited data are published regarding changes in the physicochemical properties of rice flours from germinated de-hulled rice treated by ultrasound. This work was undertaken to evaluate the effect of ultrasound treatment (25 kHz, 16 W/L, 5 min) on starch hydrolysis and functional properties of rice flours produced from ultrasound-treated red rice and brown rice germinated for up to 36 h. Environmental Scanning Electron Microscopy (ESEM) microimages showed that the ultrasound treatment altered the surface microstructure of rice, which helped to improve moisture transfer during steam-cooking. The flours from sonicated germinated de-hulled rice exhibited significantly (p < .05) enhanced starch hydrolysis, increased the glucose content, and decreased falling number values and viscosities determined by a Rapid Visco Analyzer. The amylase activity of the germinating red rice and brown rice displayed different sensitivity to ultrasonic treatment. The ultrasonic pre-treatment resulted in a significant reduction in energy use during germination with a potential to further reduce energy use in germinated rice cooking process. The present study indicated that ultrasound could be a low-power consumption method to modify the rheological behavior of germinated rice flour, as well as an efficient approach to improve the texture, flavor, and nutrient properties of steam-cooked germinated rice.

Cooking quality properties and free and bound phenolics content of brown, black, and red rice grains stored at different temperatures for six months

The changes in cooking quality and phenolic composition of whole black and red rice grains stored during six months at different temperatures were evaluated. Brown rice with known cooking quality properties and low phenolic levels was used for purposes comparison. All rice genotypes were stored at 13% moisture content at temperatures of 16, 24, 32, and 40°C. Cooking time, hardness, free and bound phenolics, anthocyanins, proanthocyanidins, and free radical scavenging capacity were analysed. The traditional rice with brown pericarp exhibited an increase in cooking time and free phenolics content, while rice with black pericarp exhibited a reduction in cooking time after six months of storage at the highest studied temperature of 40°C. There as increases in ferulic acid levels occurred as a function of storage temperature. Red pericarp rice grains showed decreased antioxidant capacity against ABTS radical for the soluble phenolic fraction with increased time and storage temperature.

Strategies for the extraction and analysis of non-extractable polyphenols from plants

The majority of studies based on phenolic compounds from plants are focused on the extractable fraction derived from an aqueous or aqueous-organic extraction. However, an important fraction of polyphenols is ignored due to the fact that they remain retained in the residue of extraction. They are the so-called non-extractable polyphenols (NEPs) which are high molecular weight polymeric polyphenols or individual low molecular weight phenolics associated to macromolecules. The scarce information available about NEPs shows that these compounds possess interesting biological activities. That is why the interest about the study of these compounds has been increasing in the last years. Furthermore, the extraction and characterization of NEPs are considered a challenge because the developed analytical methodologies present some limitations. Thus, the present literature review summarizes current knowledge of NEPs and the different methodologies for the extraction of these compounds, with a particular focus on hydrolysis treatments. Besides, this review provides information on the most recent developments in the purification, separation, identification and quantification of NEPs from plants.

Bound phenolic compounds and antioxidant properties of whole grain and bran of white, red and black rice

Total phenolic content (TPC), individual phenolic acid and antioxidant capacity of whole grain and bran fraction 18 rices with different bran color were investigated. The levels of TPC in bound fractions were significantly higher than those in the free fractions either in the whole grains or brans. The main bound phenolic acids in white rice samples were ferulic acid, p-coumaric acid, and isoferulic acid, and in pigmented rice samples were ferulic acid, p-coumaric acid, and vanillic acid. The protocatechuic acid and 2,5-dihydroxybenzoic acid were not detected in white samples. The content of gallic acid, protocatechuic acid, 2,5-dihydroxybenzoic acid, ferulic acid, sinapic acid had significantly positive correlations with TPC and antioxidant capacity. This study found much wider diversity in the phenolics and antioxidant capacity in the whole grain and brans of rice, and will provide new opportunities to further improvement of rice with enhanced levels of the phytochemicals.

Antidiabetic Potential of Purple and Red Rice (Oryza sativa L.) Bran Extracts

Pigmented rice contains anthocyanins and proanthocyanidins that are concentrated in the bran layer. In this study, we determined the phenolic, flavonoid, anthocyanin, and proanthocyanidin content of five rice bran (1 brown, 2 red, and 2 purple) extracts. Each bran extract was evaluated for inhibitory effects on α-amylase and α-glucosidase activity, two key glucosidases required for starch digestion in humans. All purple and red bran extracts inhibited α-glucosidase activity, however only the red rice bran extracts inhibited α-amylase activity. Additionally, each bran extract was examined for their ability to stimulate glucose uptake in 3T3-L1 adipocytes, a key function in glucose homeostasis. Basal glucose uptake was increased between 2.3- and 2.7-fold by exposure to the red bran extracts, and between 1.9- and 3.1-fold by exposure to the purple bran extracts. In red rice bran, the highest enzyme inhibition and glucose uptake was observed with a proanthocyanidin-enriched fraction. Both IITA red bran and IAC purple bran increased expression of GLUT1 and GLUT4 mRNA, and genes encoding insulin-signaling pathway proteins.

Bran data of total flavonoid and total phenolic contents, oxygen radical absorbance capacity, and profiles of proanthocyanidins and whole grain physical traits of 32 red and purple rice varieties

Phytochemicals in red and purple bran rice have potential health benefit to humans. We determined the phytochemicals in brans of 32 red and purple global rice varieties. The description of the origin and physical traits of the whole grain (color, length, width, thickness and 100-kernel weight) of this germplasm collection are provided along with data of total flavonoid and total phenolic contents, oxygen radical absorbance capacity and total proanthocyanidin contents. The contents and proportions of individual oligomers, from degree of polymerization of monomers to 14-mers, and polymers in bran of these 32 rice varieties are presented (DOI: http://dx.doi.org/10.1016/j.foodchem.2016.04.004) [1].