Red Rice Bran Research Articles

Anticancer properties of tocotrienols: A review of cellular mechanisms and molecular targets.

Vitamin E is composed of two groups of compounds: α-, β-, γ-, and δ-tocopherols (TPs), and the corresponding unsaturated tocotrienols (TTs). TTs are found in natural sources such as red palm oil, annatto seeds, and rice bran. In the last decades, TTs (specifically, γ-TT and δ-TT) have gained interest due to their health benefits in chronic diseases, based on their antioxidant, neuroprotective, cholesterol-lowering, anti-inflammatory activities. Several in vitro and in vivo studies pointed out that TTs also exert a significant antitumor activity in a wide range of cancer cells. Specifically, TTs were shown to exert antiproliferative/proapoptotic effects and to reduce the metastatic or angiogenic properties of different cancer cells; moreover, these compounds were reported to specifically target the subpopulation of cancer stem cells, known to be deeply involved in the development of resistance to standard therapies. Interestingly, recent studies pointed out that TTs exert a synergistic antitumor effect on cancer cells when given in combination with either standard antitumor agents (i.e., chemotherapeutics, statins, "targeted" therapies) or natural compounds with anticancer activity (i.e., sesamin, epigallocatechin gallate (EGCG), resveratrol, ferulic acid). Based on these observations, different TT synthetic derivatives and formulations were recently developed and demonstrated to improve TT water solubility and to reduce TT metabolism in cancer cells, thus increasing their biological activity. These promising results, together with the safety of TT administration in healthy subjects, suggest that these compounds might represent a new chemopreventive or anticancer treatment (i.e., in combination with standard therapies) strategy. Clinical trials aimed at confirming this antitumor activity of TTs are needed.

Optimization of Flavonoid Extraction from Red and Brown Rice Bran and Evaluation of the Antioxidant Properties.

Recently, the quality-by-design concept has been widely implemented in the optimization of pharmaceutical processes to improve batch-to-batch consistency. As flavonoid compounds in pigmented rice bran may provide natural antioxidants, extraction of flavonoid components from red and brown rice bran was optimized using central composite design (CCD) and response surface methodology (RSM). Among the solvents tested, ethanol was most efficient for extracting flavonoids from rice bran. The examined parameters were temperature, solvent percentage, extraction time, and solvent-to-solid ratio. The highest total flavonoid content (TFC) in red rice bran was predicted as 958.14 mg quercetin equivalents (QE)/100 g dry matter (DM) at 58.5 °C, 71.5% (v/v), 36.2 min, and 7.94 mL/g, respectively, whereas the highest TFC in brown rice bran was predicted as 782.52 mg QE/100 g DM at 56.7 °C, 74.4% (v/v), 36.9 min, and 7.18 mL/g, respectively. Verification experiment results under these optimized conditions showed that the TFC values for red and brown rice bran were 962.38 and 788.21 mg QE/100 g DM, respectively. No significant differences were observed between the predicted and experimental TFC values, indicating that the developed models are accurate. Analysis of the extracts showed that apigenin and p-coumaric acid are abundant in red and brown rice bran. Further, red rice bran with its higher flavonoid content exhibited higher nitric oxide and 2,2-diphenyl-1-picrylhydrazyl scavenging activities (EC50 values of 41.3 and 33.6 μg/mL, respectively) than brown rice bran. In this study, an extraction process for flavonoid compounds from red and brown rice bran was successfully optimized. The accuracy of the developed models indicated that the approach is applicable to larger-scale extraction processes.

Bioactive compounds and protective effect of red and black rice brans extracts in human neuron-like cells (SH-SY5Y)

Rice bran is obtained from the rice polishing process, and this by-product contains many bioactive compounds. In this study, the composition of phenolic compounds from red and black rice brans was determined by HPLC−DAD−MS. Additionally, the neuroprotective ability of these brans in SH-SY5Y cells insulted with hydrogen peroxide (H2O2) was evaluated. The phenolic constituents of rice bran were separated into hydrophilic and pellet fractions. The major phenolic compound in both samples was ferulic acid. Cyanidin 3-glucoside was the main anthocyanin in black rice bran. The hydrophilic and pellet fractions showed a protective effect (38–94%) on SH-SY5Y cells insulted by H2O2 in DCFH-DA assay. No extract showed cytotoxicity in the SRB assay. These results suggest a neuroprotective effect of red and black rice brans extracts due to their high antioxidant capacity, along with the absence of cytotoxicity. Thus, they may potentially be used as sources of bioactive compounds.

Phytochemical constituents, antioxidant activity, and antiproliferative properties of black, red, and brown rice bran

BackgroundIn the recent years, the health benefits of the pigmented rice varieties have reported due to the presence of bioactive compounds. In this study, the phytochemical constituents (total phenolic, flavonoid and anthocyanin content) and individual phenolics and flavonoids of the extracts of sixteen genotypes of pigmented rice bran were evaluated using spectrophotometric and ultra-high performance liquid chromatography method. Antioxidative properties of the free and bound fractions were evaluated using nitric oxide and 1,1-diphenyl-2-picrylhydrazyl scavenging assays. Extracts were evaluated for antiproliferative activity against breast cancer cell lines (MCF-7 and MDA-MB-231) using the MTT assay.ResultsSignifficant diferences were observed in the concentrations of phytochemicals and biological activities among different pigmented rice brans. The highest phytochemical content was observed in black rice bran followed by red and brown rice bran. The concentration of free individual flavonoids and phenolic compounds were significantly higher than those of bound compounds except those of ferulic acid and p-coumaric acid. Highest antioxidant activities were observed in black rice bran, followed by red and brown rice bran extracts. Extracts of black rice bran exhibited potent antiproliferative activity, with half maximal inhibitory concentrations (IC50) of 148.6 and 119.2 mg/mL against MCF-7 and MDA-MB-231 cell lines, respectively, compared to the activity of the extracts of red rice bran (175.0 and 151.0 mg/mL, respectively) and brown rice bran (382.3 and 346.1 mg/mL, respectively).ConclusionsBlack rice bran contains high levels of phytochemicals, and thus has potent pharmaceutical activity. This highlights opportunities for researcher to breed new genotypes of rice with higher nutritional values, which the food industry can use to develop new products that will compete in expanding functional food markets.

Optimization of the polyphenolics extraction from red rice bran by response surface methodology

Recently, the interest towards phenol compounds has progressed. In this study, a response surface methodology (RSM) was applied to predict the optimum conditions for extraction of phenolic from red rice bran. Firstly, the effects of ethanol concentration (20–80%), added acetic acid concentration (0–20%), extraction time (0–6.5 hours), temperature (25–100oC), number of extraction cycles (1–4) and solid–solvent ratio (1/4–1/10 w/v) on total polyphenolic content (TPC) of red rice bran were found. After that, three parameters such as solvent concentration (48–68%), added acetic acid concentration (10–15%) and extraction time (120–240 min) were able to be optimized using the Box Behnken design (BBD) with a quadratic regression model built by using RSM. The experiment was designed according to 30 runs with 2 blocks; each block consists of 3 central points and 1 replicate. This design was set up for 3 factors to optimise the response in term of TPC extraction. The extracts were analyzed the TPC spectrophotometrically according to the Folin-Ciocalteu colorimetric assay. The optimal extraction conditions were determined as follows: ethanol concentration of 54.5%, added acetic acid concentration of 13.1%, extraction time of 210 min, temperature of 40oC, 3 cycles of extraction and solid–solvent ratio 1/6 w/v. Using these extraction conditions, the experimental yield of TPC was 2391.1±5.9 mg GAE/100 g dry weight (dw) that was in close significant agreement with predicted value (p < 0.05). The experimental results were fitted to a second order quadratic polynomial model, and they have shown a good fit to the proposed model (R2 = 0.99). With these conditions, the antioxidant capacity assayed by 1,1–diphenyl–2–picrylhydrazyl (DPPH) radical–scavenging activity in term of IC50 value of extract was 108.1±2.9 μg dw/mL. The study result indicates the suitability of the developed model and the success of RSM in optimizing the extraction conditions.

In vitro inhibition of lipase, α‐amylase, α‐glucosidase, and angiotensin‐converting enzyme by defatted rice bran extracts of red‐pericarp rice mutant

AbstractBackground and objectivesFreeze‐dried aqueous and various ethanolic (25%, 50%, 75%, and 95%) extracts of defatted red rice (mutant AM‐425) bran were prepared and designated as E0, E25, E50, E75, and E95, respectively. Phenolic constituents of extracts and the in vitro inhibitory effects of extracts against lipase, α‐amylase, α‐glucosidase, and angiotensin‐converting enzyme (ACE) were examined.FindingsYields of extracts ranged from 16.45% (E0) to 11.57% (E95). The E50 and E75 had higher total phenols (79.2–80.9 mg ferulic acid equivalent (FAE)/g extract) than other extracts. The E75 and E95 had higher total flavonoids (20.46–21.35 mg catechin equivalent/g extract). The most abundant phenolic acid and flavonoid were ferulic acid and catechin, respectively. Both E50 and E75 had higher inhibitory activity against lipase (IC50, 35.95–35.97 mg/ml), α‐amylase (IC50, 21.99–22.02 mg/ml), α‐glucosidase (IC50, 1.67 mg/ml), and ACE (IC50, 2.93–2.97 mg/ml).ConclusionsBoth E50 and E75 can be used to produce high‐value functional supplements. However, further studies with in vivo models reflecting potential human benefits are needed in the future.Significance and noveltyThe tested E50 and E75 had higher contents of total phenols. Moreover, both E50 and E75 were able to inhibit key enzymes relevant to obesity (lipase), type‐2 diabetes mellitus (α‐amylase and α‐glucosidase), and hypertension (angiotensin‐converting enzyme) in an in vitro model. The results suggest that defatted rice bran extracts could be considered as potential candidates for developing functional foods or supplements.

EXTRACTION AND CHEMICAL COMPOUNDS IDENTIFICATION OF RED RICE BRAN OIL USING GAS CHROMATOGRAPHY – MASS SPECTROMETRY (GC-MS) METHOD

The objectives of the study are to obtain optimum yield of extraction red rice bran oil, to determine the physico-chemical characteristics, and componen coumpounds. Data was analyzed using Nir Parametric Statistics by Friedmann test. The result showed the optimum extraction results was obtained by the ratio of substrate : solvent of 1: 8 and the oil yield was 12.31 ±0.325%. The physico properties of red rice bran oil were greenish brown colour, with a density ranged from 0.908 ± 0.014 to 0.922 ± 0.014 (g/mL), and the water content ranged from 0.87 ± 0.06 to 0.91 ± 0.02 %. The chemical properties of red rice bran oil were: the acid number ranged from 116.41 ± 1.22 to 118.11 ± 2.45 (mg NaOH/g); the saponification number ranged from 193.74 ±21.88 to 199.62 ± 12.63 (mg KOH/g); and the peroxide number ranged from 24.37 ± 2.44 to 26.07 ± 4.88 (mgek/kg), respectively. Oils was analyzed used GC-MS. The chemical components of rice bran oil are oleic acid (46.24%), palmitic acid (18.25%), linoleic acid (13.29%), 9-octadecane(7.76%).

Optimization of enzyme-assisted improvement of polyphenols and free radical scavenging activity in red rice bran: A statistical and neural network-based approach

ABSTRACTThe current study is focused on optimizing the parameters involved in enzymatic processing of red rice bran for maximizing total polyphenol (TP) and free radical scavenging activity (FRSA). The sequential optimization strategies using central composite design (CCD) and artificial neural network (ANN) modeling linked with genetic algorithm (GA) was performed to study the effect of incubation time (60–90 min), xylanase concentration (5–10 mg/g), cellulase concentration (5–10 mg/g) on the response, i.e., total polyphenol and FRSA. The result showed that incubation time has a negative effect on the response, while the square effect of xylanase and cellulase showed positive effect on the response. A maximum TP of 2,761 mg ferulic acid Eq/100 g bran and FRSA of 778.4 mg Catechin Eq/100 g bran was achieved with incubation time (min) = 60.491; xylanase (mg/g) = 5.4633; cellulase (mg/g) = 11.5825. Furthermore, ANN-GA-based optimization showed better predicting capabilities as compared to CCD.

Discrimination of red and white rice bran from Indonesia using HPLC fingerprint analysis combined with chemometrics.

HPLC fingerprint analysis combined with chemometrics was developed to discriminate between the red and the white rice bran grown in Indonesia. The major component in rice bran is γ-oryzanol which consisted of 4 main compounds, namely cycloartenol ferulate, cyclobranol ferulate, campesterol ferulate and β-sitosterol ferulate. Separation of these four compounds along with other compounds was performed using C18 and methanol-acetonitrile with gradient elution system. By using these intensity variations, principal component and discriminant analysis were performed to discriminate the two samples. Discriminant analysis was successfully discriminated the red from the white rice bran with predictive ability of the model showed a satisfactory classification for the test samples. The results of this study indicated that the developed method was suitable as quality control method for rice bran in terms of identification and discrimination of the red and the white rice bran.

Experimental treatment of antipsychotic-induced movement disorders.

Antipsychotic drugs are extensively prescribed for the treatment of schizophrenia and other related psychiatric disorders. These drugs produced their action by blocking dopamine (DA) receptors, and these receptors are widely present throughout the brain. Therefore, extended antipsychotic use also leads to severe extrapyramidal side effects. The short-term effects include parkinsonism and the later appearing tardive dyskinesia. Currently available treatments for these disorders are mostly symptomatic and insufficient, and are often linked with a number of detrimental side effects. Antipsychotic-drug-induced tardive dyskinesia prompted researchers to explore novel drugs with fewer undesirable extrapyramidal side effects. Preclinical studies suggest a role of 5-hydroxytryptamine (serotonin)-1A and 2A/2C receptors in the modulation of dopaminergic neurotransmission and motivating a search for better therapeutic strategies for schizophrenia and related disorders. In addition, adjunctive treatment with antioxidants such as vitamin E, red rice bran oil, and curcumin in the early phases of illness may prevent additional oxidative injury, and thus improve and prevent further possible worsening of related neurological and behavioral deficits in schizophrenia. This review explains the role of serotonergic receptors and oxidative stress, with the aim of providing principles for prospect development of compounds to improve therapeutic effects of antischizophrenic drugs.

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.

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

Proanthocyanidins, a flavonoids subgroup, are proposed to have chronic disease modulation properties. With the eventual goal of enhancing rice phytonutrient concentrations, we investigated the genotypic variation of the concentrations of individual oligomers and polymers of proanthocyanidins in red and purple rice brans. A 4.3-fold variation in total proanthocyanidins (sum of oligomers and polymers) in the extractable fraction was found and the concentration was highly correlated with total phenolics, total flavonoids and antiradical capacity. Variation in the proportion of oligomers and polymers existed, with monomers to trimers, 4–6mers, 7–10mers and polymers accounting for 7, 18, 26.5 and 48.7%, respectively, of the total. The redness value a∗ of whole grain rice measured in CIE L∗a∗b∗ color space was negatively and positively correlated with extractable and non-extractable proanthocyanidins, respectively. The variation found indicates it is possible to select rice with bran containing high levels of total proanthocyanidins and specific degree of polymerization profiles.

Correlation of pasting behaviors with total phenolic compounds and starch digestibility of indigenous pigmented rice grown in upper Northern Thailand

Background: Thailand has one of the most important rice genetic resources with white, light brown, brown, red, and purple rice bran colors. The latter believed to have potential for health benefits due to their phenolic content. Recently researchers have indicated that starch digestive enzymes, including salivary and pancreatic α-amylases and α-glucosidases, can be inhibited by phenolic compounds. Although pasting properties of rice flour are key determinants of quality significantly impacting the final product texture, there is no in-depth study on their correlation with phenolic compound and starch digestibility. Methods: Rice flour from twelve varieties, three from each of five bran colors (white, brown, red, and purple), were evaluated for pasting properties (RVA-3D), total phenolic compounds, amylose content, resistant starch and estimated glycemic index. Simple correlation coefficients were calculated for the relationships between pasting properties (final viscosity, breakdown, setback and pasting temperature) and total phenolic compounds, resistant starch and estimated glycemic index.Results: Within each rice variety, red and purple pigmented flours had higher total phenolic compounds (TPC) and more resistant starch than that of white flours. The TPC and resistant starch content of the flours ranged between 7.83- 47.3 mg/L and 2.44–10.50% respectively, and producing 60-80 of estimated glycemic index. Viscosity behavior showed that pigmented with low amylose rice had lower viscosity temperature than that of pigmented with high amylose rice flour, but higher in peak viscosity. Correlation coefficients of pasting temperature, final viscosity, break down and setback with TCP was observed to be inversely related to glycemic index. However, it was positively correlated to the resistant starch and amylose content. Conclusions: Pigmented rice flour is a better source of TPC and resistant starch which in turn provides low glycemic index. This could help reduce the onset of type 2 diabetes and other related chronic diseases. In addition, this study provides impact of pasting behavior – TPC- resistant starch of rice flour relationships, which have important implication for utilization in food industry.Keywords: total phenolic compounds, amylose content, resistant starch, glycemic index

Bioactive compounds and antioxidative activity of colored rice bran

The profiles of bioactive compounds (including phenolics and flavonoids in free and bound fractions, anthocyanins, proanthocyanidins, vitamin E, and γ-oryzanol) of outer and inner rice bran from six colored rice samples collected from local markets were investigated. Proanthocyanidins could only be detected in red rice bran but not in black rice bran. The free fraction of the extracts dominated the total phenolics (72–92%) and the total flavonoids (72–96%) of colored rice bran. Most of the phenolic acids (83–97%) in colored rice bran were present in the bound form. Protocatechualdehyde was identified for the first time in the bound fraction of red rice bran by high performance liquid chromatography-photodiode array/electrospray ionization tandem mass spectrometry. The antioxidative activities of the free fraction of the colored rice bran were attributed to the proanthocyanidins in red colored rice and anthocyanins in black rice, while that of the bound fraction was mainly due to the phenolic acids.

Effect of Red Yeast Rice and Coconut, Rice Bran or Sunflower Oil Combination in Rats on Hypercholesterolemic Diet.

Dietary supplements provide a novel population based health approach for treating hyperlipidemias. Red yeast rice is known to have lipid lowering effects. Combination of red yeast rice with various oils is taken by different population around the world. In this present work, we aimed to compare the effects of red yeast rice with different oil (coconut, rice bran and sunflower oil) supplementations on lipid levels and oxidative stress in rats fed on hypercholesterolemic diet. A Randomized controlled study was conducted on 28 male Sprague Dawley rats. It included 4 arms-Control arm (hypercholesterolemic diet), Test arm A (hypercholesterolemic diet +Red yeast rice + Rice bran oil), arm B (hypercholesterolemic diet +Red yeast rice + Coconut oil) and arm C (hypercholesterolemic diet +Red yeast rice + Sunflower oil). At the end of one month, serum cholesterol, triglycerides, MDA and paraoxonase was measured. The mean values of analytes between the different groups were compared using student 't-' test. The rats fed with red yeast rice and rice bran oil combination showed significantly lower levels of serum cholesterol, triglycerides and MDA when compared to the controls. The serum paraoxonase levels were significantly higher in this group when compared to the controls. The rats fed with red yeast rice and coconut oil combination showed significantly lower serum cholesterol and MDA levels when compared to the controls. The mean triglyceride and paraoxonase levels did not show any statistically significant difference from the controls. The rats on red yeast rice and sunflower oil combination did not show any statistically significant difference in the lipid levels and oxidative stress parameters. The food combination which had best outcome in preventing the development of hyperlipidemia and oxidative stress in rats fed with hypercholesterolemic diet was red yeast rice and rice bran oil. Combining red yeast rice with coconut oil and sunflower oil gave suboptimal benefits.

Quality Improvement of Reduced‐Salt, Phosphate‐Free Fish Patties from Processed By‐Products of Nile Tilapia Using Textural Additives and Bioactive Rice Bran Compounds

AbstractOver 60% of tilapia by‐products from the frozen fillet industry are wasted. In response to the increased health consciousness of consumers, we investigated the effects of lowered salt content, phosphate substitute additives and natural antioxidants on the quality improvement of patties made from processed by‐products of tilapia. We determined the effect of 0.5% k‐carrageenan, Citri‐Fi 100 fine granulated and xanthan gum combined with 0.5% microbial transglutaminase and 0.3% NaHCO3 on the textural qualities of reduced‐salt (1% NaCl) Nile tilapia patties (made from an 80:20 ratio of trimmed meat to belly flap) then compared this with a control with sodium tripolyphosphate (0.3%). After 12 freeze‐thaw cycles, k‐carrageenan was observed to improve the textural quality and lower cooking losses better than other treatments (P ≤ 0.05). Rice bran protein hydrolysate and red jasmine rice bran extract (2%) could be used instead of butylated hydroxyanisole (0.02%) to prevent lipid oxidation in reduced‐salt, k‐carrageenan‐supplemented patties during freezing and thawing.Practical ApplicationsThailand boasts robust production, consumption and export of Nile tilapia (Oreochromis niloticus Linn); notwithstanding, over 60% of by‐products are discarded including the trimmed and belly flap meat. These are, however, low‐value, high‐fat meats, which limit shelf life and create an undesirable flavor and texture in processed products. Appropriate textural additives (i.e., MTGase, various hydrocolloids) and natural antioxidants (i.e., bioactive rice bran compounds) are promising as additives because they enhance the textural qualities and stability in reduced‐salt, phosphate‐free fish patties made from processed tilapia by‐products. Supportive findings would lead to efficient, industrial‐scale use of these by‐products.

Evaluation of antioxidant activities and phenolic subtype contents of ethanolic bran extracts of Thai pigmented rice varieties through chemical and cellular assays

SummaryThis study revealed that the ethanolic bran extracts of 11 Thai pigmented (red and purple) and 2 nonpigmented rice varieties exerted scavenging activity against DPPH and ABTS radicals and ROS in HL‐60 cells in the following order: red &gt; purple &gt; nonpigmented rice. These rice extracts also showed the same order of phenolic and flavonoid contents, which were strongly correlated with their scavenging activity. Phenolic subtype analysis further indicated that proanthocyanidins as well as anthocyanins and protocatechuic acid contributed directly to antioxidant capacity in red and purple rice bran, respectively. In contrast, these pigmented rice bran extracts possessed moderate chelating activity partly attributed to their contents of phenolics and flavonoids, especially proanthocyanidins in red rice bran. Moreover, rice bran extracts significantly restored SOD and CAT activities in oxidative stress‐induced A549 cells. This study provides new insights on the intracellular potent antioxidant capacity of pigmented rice bran extracts in the cell‐based systems.

Suppression and Treatment of Haloperidol Induced Extrapyramidal Side Effects and Anxiety Syndrome by the Coadministeration of Red Rice Bran Oil in Rats

Antipsychotic medications may reduce or eliminate symptoms of psychosis. They are not a 'cure' for mental illnesses, but can be an effective part of treating mental disorders. Even though many of the antipsychotics such as haloperidol cannot cure mental illnesses, they are effective in eliminating or reducing psychotic symptoms. However, prolong administration of haloperidol may result in parkinsonian like effects and tardive dyskinesia. The objective of the present research was to determine the effects of long term co-administration of RRBO in diet on haloperidol induced anxiety and EPS. It was hypothesized that co-administration of RRBO by the free radicals scavenging property could alleviate parkinsonian like effects and tardive dyskinesia. The present results showed a reversal of haloperidol induced parkinsonian like effects and tardive dyskinesia in rats cotreated with RRBO.

STABILITAS AKTIVITAS ANTIOKSIDAN EKSTRAK BEKATUL BERAS MERAH TERHADAP OKSIDATOR DAN PEMANASAN PADA BERBAGAI pH [Stability of Antioxidant Activity of Red Rice Bran Extract Subjected to Oxidator and Heating in Various pH

Rice bran is acknowledged as the highest nutritious part of rice grain as well as rich in bioactive phytochemicals. Coloured rices are reported as potent sources of antioxidants therefore are regarded as viable source of antioxidants for functional foods. The aim of this study was to extract the bioactive component of red rice bran, and further the component was subjected to antioxidant activity and stability tests. The research design was a factorial randomized complete design with two factors. The first factor was the pH of the m aceration that consisted of 3 levels, i.e. 1, 2.5, and 4 . The second factor was the ratio s of bran and solvent that consisted of 4 levels, namely: 1:4, 1:6, 1:8, and 1:10. Total phenol, total anthocyanin and antioxidant activity were measured. The results showed that extraction at the pH of 1 and under the optimized conditions of a material–solvent ratio of 1:10 (wt./vol.) p roduced the most potent extract. This treatment resulted in 5.45 mg/100 g of total anthocyanins, 743.51 mg/100 g of total phenolics, 92.19% of antioxidant activity , and 441.74 mg/L of IC 50 . Reduction of the antioxidant activities as a result of heating of the red rice bran extract was greater than that of oxid ator.

Evaluation of antioxidant activities and contents in bran extracts of Thai pigmented rice using chemical and cellular assays

Due to adverse effects of synthetic antioxidants, pigmented rice has become attractive as potential sources of natural antioxidants to prevent oxidative stress implicated in many chronic diseases. In the present study, antioxidant activities of ethanol-water (70:30, v/v) bran extracts of 11 Thai pigmented rice (red and purple) and 2 non-pigmented rice varieties were evaluated by chemical assays (DPPH and ABTS radical scavenging and ferrous ion chelating assays) and cellular assays (intracellular free radical scavenging activity-NBT and DCF assays). Also, contents of total phenolics and their subtypes (flavonoids, proanthocyanidins, and anthocyanins) were assessed using colorimetric assays. Correlations between these contents and antioxidant activities were further analyzed. The results revealed that the pigmented rice bran extracts exhibited higher scavenging activity in chemical assays (IC50= 5.3 – 46.9 µg/ml) and in NBT (% inhibition = 12.3 – 62.6%) and DCF (% inhibition = 31.4 – 70.2%) assays at 30 µg/ml as compared to the non-pigmented rice extracts. High correlations between such activity and contents of phenolics and flavonoids indicated their contribution to the strong scavenging activity in red rice followed by purple rice bran extracts. In particular, noticeably high contents of proanthocyanidins in red bran and anthocyanins in purple bran as well as their positive correlations with the scavenging activity strongly suggest that they are the phenolic subtype mainly accounting for such strong activity in these rice varieties. In addition, the pigmented rice bran extracts demonstrated modulate ferrous ion chelating activity (IC50= 0.62 – 0.87 mg/ml) and modulate correlations of such activity with contents of phenolics and flavonoids. In particular for the red rice bran extracts, this activity was partly due to the presence of proanthocyanidins. Thus, pigmented rice bran extracts are abundant, safe, and inexpensive sources of potent natural antioxidants.