Differential Effects of In Vitro Simulated Digestion on Antioxidant Activity and Bioaccessibility of Phenolic Compounds in Purple Rice Bran Extracts.

Pigmented rice varieties are abundant in phenolic compounds. Antioxidant activity and bioaccessibility of phenolic compounds are modified in the gastrointestinal tract. After in vitro simulated digestion, changes in antioxidant activity and bioaccessibility of phenolic compounds (phenolic acids, flavonoids, and anthocyanins) in purple rice brans (Hom Nil and Riceberry) were compared with undigested crude extracts. The digestion method was conducted following the INFOGEST protocol. Antioxidant activity was determined using the ferric-reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity assays. The bioaccessibility index (BI) was calculated from the ratio of digested to undigested soluble phenolic content. Overall results showed that the in vitro simulated digested rice brans had lower antioxidant activity and lower total phenolic, flavonoid, and anthocyanin contents. However, the concentration of sinapic acid was stable, while other phenolic acids (gallic, protocatechuic, vanillic, ρ-coumaric, and ferulic acids) degraded after the oral, gastric, and intestinal phases. The BI of sinapic, gallic, vanillic, and ferulic acids remained stable, and the BI of quercetin was resistant to digestion. Conversely, anthocyanins degraded during the intestinal phase. In conclusion, selective phenolic compounds are lost along the gastrointestinal tract, suggesting that controlled food delivery is of further interest.

The nutritional profile and human health benefit of pigmented rice and the impact of post-harvest processes and product development on the nutritional components: A review.

Pigmented rice has attracted considerable attention due to its nutritional value, which is in large conferred by its abundant content of phenolic compounds, considerable micronutrient concentrations, as well as its higher resistant starch and thereby slower digestibility properties. A wide range of phenolic compounds identified in pigmented rice exhibit biological activities such as antioxidant activity, anti-inflammatory, anticancer, and antidiabetic properties. Post-harvest processes significantly reduce the levels of these phytochemicals, but recent developments in processing methods have allowed greater retention of their contents. Pigmented rice has also been converted to different products for food preservation and to derive functional foods. Profiling a large set of pigmented rice cultivars will thus not only provide new insights into the phytochemical diversity of rice and the genes underlying the vast array of secondary metabolites present in this species but also provide information concerning their nutritional benefits, which will be instrumental in breeding healthier rice. The present review mainly focuses on the nutritional composition of pigmented rice and how it can impact human health alongside the effects of post-harvest processes and product development methods to retain the ambient level of phytochemicals in the final processed form in which it is consumed.

Influence of γ-irradiation on physicochemical, functional, proximate, and antioxidant characteristics of pigmented rice flours.

In recent years, food irradiation using γ-rays is one of the most valuable practices for insect disinfestation in rice grains for extended shelf life. In this study, flours from four pigmented rice cultivars were exposed to γ-irradiation using 60Co at different doses (0, 5, 10, and 15 kGy). The impact of γ-irradiation on the physico-chemical, functional, and morphological characteristics of pigmented rice flours were analyzed. Results revealed that reduction in amylose content, pH, bulk density, tapped density, and syneresis, while solubility, water absorption capacity, and swelling power values increased significantly (p < 0.05). Pasting characteristics of pigmented rice flours also reduced after exposure to γ-irradiation. Morphological features of pigmented rice flour granules revealed no evidence of physical destruction after irradiation except for black kavuni flour. The structural analysis by FTIR confirms no effect of γ-irradiation on pigmented rice flours. Overall, the study revealed that irradiated pigmented rice flours with enhanced functional properties of less than 10 kGy can be effectively used in the development of value-added rice-based food products considering all the beneficial and safety aspects. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-023-05709-z.

Grain and Leaf Anthocyanin Concentration Varies among Purple Rice Varieties and Growing Condition in Aerated and Flooded Soil.

Anthocyanins are a group of pigments responsible for the red-blue color in plant parts, and have potential for health benefits and pharmaceutical ingredients. To evaluate whether anthocyanin concentrations in five purple rice varieties could be varied by water condition, plants were grown in waterlogged and aerobic (well-drained) soil. Grain anthocyanin concentration and grain yield were measured at maturity, while leaf anthocyanin concentrations were measured at booting and flowering stages. Four varieties grown under the waterlogged condition had 2.0−5.5 times higher grain anthocyanin than in the aerobic condition. There was a positive relationship between grain and leaf anthocyanin at booting in the waterlogged condition (r = 0.90, p < 0.05), while grain and leaf anthocyanin were positively correlated at flowering in both the waterlogged (r = 0.88, p < 0.05) and aerobic (r = 0.97, p < 0.01) conditions. The results suggest that water management should be adopted as a practical agronomic tool for improving the anthocyanin concentration of purple rice for specialist markets, but the specific responses between rice varieties to water management should be carefully considered.

Identification and characterization of drought-tolerant local pigmented rice from Indonesia.

Water is essential to support life. Because limited water availability may affect their life cycles, plants have developed multiple responses to drought stress. Plant physiological and metabolic changes during drought may reflect changes that occur at the level of gene expression. In this study, we investigated the variation in drought-mitigating strategies employed by pigmented rice (Oryza sativa) varieties and the genes involved in their possible drought tolerance. We screened 21 local pigmented rice cultivars from Indonesia for increased drought tolerance using the fraction transpirable soil water method to exert precise control of the drought stress imposed on plants. We then determined the expression of OsDREB1A, OsNAC6, OsNHX1, OsCuZnSOD2, OsOSCAT2, and OsCAT3 in plants grown under well-watered conditions and under moderate or severe drought stress. Among the pigmented rice cultivars, Merah Pari Eja had the greatest drought tolerance, while the red rice Inpari 24 had the highest mortality rate (60%). We also included the white rice cultivar Putih Payo, which is fully sensitive to drought (with 100% mortality under the conditions used) as a negative control. Gene expression profiling revealed a general upregulation of drought-related genes in Merah Pari Eja and a downregulation of such genes in the other two cultivars. Measurements of antioxidant enzyme activity, leaf damage, free radicals, chlorophyll, and anthocyanin contents provided further evidence that Merah Pari Eja is more drought tolerant than the other two cultivars. We conclude that OsDREB1A, OsNAC6, OsNHX1, OsCuZnSOD2, OsOSCAT2 and OsCAT3 expression patterns can reveal plants that have increased drought tolerance.

Dipeptidyl peptidase-4 (DPP-4) inhibitory activity and glucagon-like peptide (GLP-1) secretion in arsenically safe pigmented red rice (Oryza sativa L.) and its product.

Inhibition of DPP-4 and stimulation of GLP-1 secretion are therapeutic strategies for controlling glycaemia in type 2 diabetes. The present study assessed the DPP-4 inhibitory activity and GLP-1 secretory action of pigmented and non-pigmented rice (Oryza sativa L.), along with an extruded food product. Cereal-based extruded food products, with or without passion fruit powder, were prepared from red rice using a twin extruder. Optimal extrusion conditions were determined using a CCD of response surface methodology resulting in optimal conditions to be 97.5 °C, a screw speed of 250 rpm, feed moisture of 25.2% and addition of 11.25% passion fruit powder. Samples were sequentially extracted in n-hexane, ethanol (50%) and water. Ethanol/water (50:50) extracts of rice bran significantly inhibited DPP-4 activity by 70.48 ± 1.06%, comparing favourably with RR (42.55 ± 0.84%), PRR (35.91 ± 1.27%) and PA (29.14 ± 1.23%). DPP-4 inhibitory activity was retained in both extruded products albeit at reduced levels. GLP-1 secretion was stimulated mostly by extruded products extracted with n-hexane or ethanol which upregulated basal secretion by 6.1-fold and 4.2-fold, respectively. ICP-MS results showed that extruded food items have a lower arsenic content. In conclusion, there are potential opportunities for the nutraceuticals and functional food products using pigmented red rice. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-022-05444-x.

OsMYB3 is a R2R3-MYB gene responsible for anthocyanin biosynthesis in black rice.

Black rice is a rare type of rice germplasm with various health benefits that are largely attributed to anthocyanin pigment accumulation in the pericarps. The anthocyanin biosynthesis in plant tissues is activated mainly by the MBW complexes, consisting of three types of transcription factors R2R3-MYB, bHLH, and WDR. In black rice, the bHLH and WDR components regulating anthocyanin biosynthesis in pericarps have been characterized, while the R2R3-MYB factor remains unknown. By examining the expression correlation between all putative rice MYB genes and anthocyanin biosynthesis-related genes based on transcriptome data of pericarps in combination with further molecular and genetic analysis, we proved that OsMYB3 (LOC_Os03g29614) was the determinant R2R3-MYB gene for anthocyanin biosynthesis in rice pericarps. The expression level of OsMYB3 in pericarps of black rice was significantly higher than that of white rice. The knockout of OsMYB3 in a black rice variety caused significant downregulation of 19 anthocyanin metabolites and many other flavonoids in grains. Our research deepens the understanding of regulatory system for anthocyanin biosynthesis in rice pericarps and provides implications for breeding black rice varieties with high anthocyanin level. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-021-01244-x.

Differential expression of flavonoid biosynthesis genes and biochemical composition in different tissues of pigmented and non-pigmented rice.

Ever since the flavonoids and other antioxidants in rice were demonstrated with immense health benefits, much interest has been diverted to study the native indigenous rice landraces. In the present investigation, three pigmented rare Indian rice landraces and two non-pigmented rice varieties were analyzed for their phytoconstituents like total phenolic content (TPC), total flavonoid content (TFC), total anthocyanin content and antioxidant potential using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity. The phytochemical profile was compared between seed, seedling, stem, leaf and root tissues of the different varieties. Pigmented rice cultivars demonstrated higher levels of bioactive compounds as compared to the non-pigmented cultivars exhibiting a strong correlation between the antioxidant activity of the grain and their phenolic and flavonoid content. Among the five different rice studied, black navara was found to be superior in terms of its phytochemical composition. Further, the expression levels of flavonoid genes among pigmented and non-pigmented rice was studied. Higher gene expression profiles were observed in the 8 flavonoid genes studied in pigmented rice varieties as compared to non-pigmented varieties. The colorlessness of non-pigmented rice and its lower levels of phytoconstituents correlated with the low transcript levels of flavonoid genes recorded in them. This study provides a basis for understanding the health-promoting properties of pigmented rice over non-pigmented rice at the biochemical and molecular levels.

Production of innovative gluten-free breakfast cereals based on red and black rice by extrusion processing technology.

The transformation of black and red, broken or not, whole rice grains, into breakfast cereals is an interesting way to add value to these snacks for some reasons. Firstly, broken kernels hardly achieve a high market value; whole rice is healthy not only for their nutrient contents but also for their phytochemical profile, rich in phenolic compounds; breakfast cereals from pigmented rice are colored by themselves, and any additional colorant is unneeded; finally, rice is naturally gluten-free and suitable for those with conditions like celiac disease or gluten sensitivity. The objective of this study was to optimize some extrusion parameters that account for the physicochemical properties of extrudates by using response surface methodology. Feed moisture between 15 and 21% and the 4th barrel zone temperature between 110 and 160 °C were the independent variables. Specific features such as color, texture, water solubility and absorption, cold viscosity, expansion, specific volume, and compression force were evaluated. The trials have shown that moisture had a higher impact on the extrusion process than temperature. Less expanded, denser, harder, and darker products were obtained at higher moisture levels. The optimum points were defined at 15.5% and 16.0% of feed moisture and 159 °C and 150 °C of temperature for black and red rice extrudates, respectively. These conditions resulted in cereal breakfast balls with optimal water solubility, volume, texture, and good color. Additionally, cold viscosities and a low compression led to products with a potential high approval by consumers.

Diversity in γ-oryzanol profiles of Japanese black-purple rice varieties.

The γ-oryzanol contents and the composition of steryl ferulates distributed in Japanese pigmented rice varieties were investigated using the high-performance liquid chromatography-ultraviolet detection method for the purpose of expanding their utilisation. The average γ-oryzanol content in nine black-purple, four red, four green and three brown rice varieties was 54.2, 47.3, 44.3 and 43.3 mg γ-oryzanol equivalent/100 g dried weight, respectively. Among the nine varieties of black-purple rice, five varieties showed steryl ferulate composition similar to that of brown, red and green varieties. In contrast, the composition of steryl ferulates in other four black-purple rice varieties was partially specific and was characterised by a low amount of campesteryl ferulate and high of campestanyl ferulate and stigmastanyl ferulate. The latter two steryl ferulates have been recognised as minor components of γ-oryzanol in rice and as major components in wheat and corn. These results indicate that the compositions of steryl ferulates vary among Japanese black-purple rice varieties.

Milling and thermal treatment induced changes on phenolic components and antioxidant activities of pigmented rice flours.

Processing methods involved in value addition to pigmented broken rice, a milling by-product may affect the nutraceutical qualities. Hence the effect of pulverisation and toasting on nutraceutical content in brown rice flours of red and black rice varieties were studied. Plate milling reduced soluble, bound and total polyphenols in red, but increased in black; increased insoluble polyphenols and oryzanol, and reduced anthocyanin in both varieties; antioxidant activity is reduced in red, but increased in black. Toasting caused reduction of soluble, insoluble and total polyphenol, anthocyanin and antioxidant activity in both varieties with an increase in bound polyphenols, and retention of flavonoids and oryzanol. HPLC characterization of phenolics showed changes on processing in content of catechin, caffeic, vanillic, protocatechuic and ferulic acid. It can be concluded that processing impacts the phenolic components of pigmented broken brown rice flour and this information is useful for functional food industry.

Applying nitrogen fertilizer increased anthocyanin in vegetative shoots but not in grain of purple rice genotypes.

BACKGROUND: Anthocyanin is a major antioxidant compound in purple rice, with properties that can protect against oxidative damage in some human diseases. This study was undertaken to determine if nitrogen (N) fertilizer can enhance anthocyanin and antioxidant levels in four purple Thai rice genotypes. RESULTS: The anthocyanin concentration and antioxidant capacity were increased in the shoots of N120 plants compared with plants without N. The leaves had higher anthocyanin concentration and antioxidant capacity than the stem+leaf sheath. Maximum shoot anthocyanin concentrations occurred at tillering and then declined by 87-94% at maturity. Antioxidant capacity was high at tillering and panicle initiation and declined by 26% in leaves and by 98% in the stem+leaf sheath at maturity. Unlike in the vegetative shoot, grain anthocyanin was not affected by the addition of N fertilizer. The response of grain antioxidant capacity to N fertilizer was affected by genotype, increasing in KPY by 45% but decreasing in K19959 by 30% in N120 plants. CONCLUSION: Applying N fertilizer could be a promising way to improve the antioxidative properties in vegetative parts for use in rice-grass juice, cosmetics and other products, especially the young leaves, which contained high values of anthocyanin as well as antioxidant capacity. However, further field studies should be undertaken to optimize N utilization for anthocyanin and antioxidant capacity in purple rice genotypes. © 2018 Society of Chemical Industry.

Evaluation of variability and environmental stability of grain quality and agronomic parameters of pigmented rice (O. sativa L.).

Eleven pigmented rice genotypes were evaluated to estimate genetic parameters, heritability and association. The results indicated that, genotypic variation was high among the lines. The distinct seasonal effect on plant performance for antioxidant capacity, anthocyanin, flavonoids, head rice recovery and test weights was also observed. Wet season favoured the crop performance in all genotypes as compared to drought conditions. The differential accumulation of different quality traits such as AOA, anthocyanin content, flavonoids content, etc showed high heritability, which would be transfer to high yeilding popular rice cultivars through conventional or geneticaly modification techniques. The line Mamihunger was chosen as donor of the high-quality rice grain and Annapurna for high yield. Further, Mamihunger are foreseen to be good in nutritional quality and industry use.

Molecular and Biochemical Analysis of Two Rice Flavonoid 3'-Hydroxylase to Evaluate Their Roles in Flavonoid Biosynthesis in Rice Grain.

Anthocyanins and proanthocyanidins, the major flavonoids in black and red rice grains, respectively, are mainly derived from 3',4'-dihydroxylated leucocyanidin. 3'-Hydroxylation of flavonoids in rice is catalyzed by flavonoid 3'-hydroxylase (F3'H: EC 1.14.13.21). We isolated cDNA clones of the two rice F3'H genes (CYP75B3 and CYP75B4) from Korean varieties of white, black, and red rice. Sequence analysis revealed allelic variants of each gene containing one or two amino acid substitutions. Heterologous expression in yeast demonstrated that CYP75B3 preferred kaempferol to other substrates, and had a low preference for dihydrokaempferol. CYP75B4 exhibited a higher preference for apigenin than for other substrates. CYP75B3 from black rice showed an approximately two-fold increase in catalytic efficiencies for naringenin and dihydrokaempferol compared to CYP75B3s from white and red rice. The F3'H activity of CYP75B3 was much higher than that of CYP75B4. Gene expression analysis showed that CYP75B3, CYP75B4, and most other flavonoid pathway genes were predominantly expressed in the developing seeds of black rice, but not in those of white and red rice, which is consistent with the pigmentation patterns of the seeds. The expression levels of CYP75B4 were relatively higher than those of CYP75B3 in the developing seeds, leaves, and roots of white rice.

Advancements in understanding low starch hydrolysis in pigmented rice: A comprehensive overview of mechanisms.

This review explores the health-promoting properties of pigmented rice, focusing on its unique ability to promote slow starch digestion and improve blood sugar regulation. While the impact of slow starch digestibility is widely acknowledged, our current understanding of the underlying mechanisms remains insufficient. Therefore, this review aims to bridge the gap by examining the intricate factors and mechanisms that contribute to the low starch hydrolysis of pigmented rice to better understand how it promotes slower starch digestion and improves blood sugar regulation. This paves the way for future advancements in utilizing pigmented rice by enhancing our understanding of the mechanisms behind low starch hydrolysis. These may include the development of food products aimed at mitigating hyperglycemic symptoms and reducing the risk of diabetes. This research broadens our understanding of pigmented rice and facilitates the development of strategies to promote health outcomes by incorporating pigmented rice into our diets.

Comparative Metabolic Profiling of Different Colored Rice Grains Reveals the Distribution of Major Active Compounds and Key Secondary Metabolites in Green Rice.

Pigmented rice grains are important resources for health and nutritional perspectives. Thus, a thorough dissection of the variation of nutrients and bioactive metabolites in different colored rice is of global interest. This study applied LC-MS-based widely targeted metabolite profiling and unraveled the variability of metabolites and nutraceuticals in long grain/non-glutinous black (BR), red (RR), green (GR), and white rice (WR) grains. We identified and classified 1292 metabolites, including five flavonoid compounds specific to BR. The metabolite profiles of the four rice grains showed significant variation, with 275-543 differentially accumulated metabolites identified. Flavonoid (flavone, flavonol, and anthocyanin) and cofactor biosynthesis were the most differentially regulated pathways among the four rice types. Most bioactive flavonoids, anthocyanidins (glycosylated cyanidins and peonidins), phenolic acids, and lignans had the highest relative content in BR, followed by RR. Most alkaloids, amino acids and derivatives, lipids, and vitamins (B6, B3, B1, nicotinamide, and isonicotinic acid) had higher relative contents in GR than others. Procyanidins (B1, B2, and B3) had the highest relative content in RR. In addition, we identified 25 potential discriminatory biomarkers, including fagomine, which could be used to authenticate GR. Our results show that BR and RR are important materials for medicinal use, while GR is an excellent source of nutrients (amino acids and vitamins) and bioactive alkaloids. Moreover, they provide data resources for the science-based use of different colored rice varieties in diverse industries.

Machine learning approach for high-throughput phenolic antioxidant screening in black Rice germplasm collection based on surface FTIR.

Pigmented rice contains beneficial phenolic antioxidants but analysing them across germplasm collections is laborious and time-consuming. Here we utilised rapid surface Fourier transform infrared (FTIR) spectroscopy and machine learning algorithms (ML) to predict and classify polyphenolic antioxidants. Total phenolics, flavonoids, anthocyanins, and proanthocyanidins were quantified biochemically from 270 diverse global coloured rice collection and attenuated total reflectance (ATR) FTIR spectra were obtained by scanning whole grain surfaces at 800-4000 cm-1. Five ML classification models were optimised using the biochemical and spectral data which performed predictions with 93.5%-100% accuracy. Random Forest and Support Vector Machine models identified key FTIR peaks linked to flavonols, flavones and anthocyanins as important model predictors. This research successfully established direct and non-destructive surface chemistry spectroscopy of the aleurone layer of pigmented rice integrated with ML models as a viable high-throughput platform to accelerate the analysis and profiling of nutritionally valuable coloured rice varieties.

Comprehensive lipidomic insights of differentially accumulating lipids in large pigmented rice sprout collection and the changes in the starch composition upon germination.

Germination represents a vital bioprocess characterized by numerous biochemical transformations that significantly influence the nutritional characteristics of rice. The mobilization of starch and lipids during germination plays a pivotal role in altering the dietary profile of rice, thus potentially addressing the nutritional requirements of populations heavily reliant on rice as a staple food. To explore this potential, a comprehensive analysis encompassing lipidomics and starch composition was conducted on a diverse collection of pigmented rice sprouts. High-resolution mass spectrometry unveiled substantial shifts in the lipidome of pigmented rice sprouts, showcasing a notable enrichment in carotenoids and unsaturated triglycerides, with potential human health benefits. Notably, purple rice sprouts exhibited heightened levels of alpha- and beta-carotene. Analysis of starch composition revealed slight changes in amylose and amylopectin content; however, a consistent increase in digestible carbohydrates was observed across all rice varieties. Germination also led to a reduction in resistant starch content, with purple rice sprouts demonstrating a pronounced two-fold decrease (p < 0.05). These changes were corroborated by a 1.33% decrease in gelatinization enthalpy and a 0.40% reduction in the melting of the amylose-lipid complex. Furthermore, pasting property analysis indicated a substantial 42% decrease in the complexation index post-germination. We posit that the insights garnered from this study hold significant promise for the development of novel products enriched with health-promoting lipids and characterized by unique flour properties.

Assessment of macro, trace and toxic element intake from rice: differences between cultivars, pigmented and non-pigmented rice.

Pigmented and non-pigmented rice varieties (grown in different areas) were collected in China, Yunnan, to investigate the content of macro-, trace elements and potentially toxic elements (PTEs), and to assess the health risk associated with dietary intake. The order of elemental concentrations in rice was Mn > Zn > Fe > Cu > Se for trace elements, P > K > Mg > Ca > Na for macro elements, and Cr > As > Cd for PTEs. Rice with a high concentration of essential elements also associated with a high content of PTEs. In addition, higher content of Cr, Mn and Na were found in pigmented rice. The health risk assessment showed that the daily intake of all elements was below the tolerable limit (UL). Moreover the intake of Fe, Zn and Se was far from sufficient for the nutrient requirement. The PTEs in rice dominated the health risk. Of concern is that this rice consumption is likely to contribute to carcinogenic risks in the long term and that adults are at higher health risk from pigmented rice compared to non-pigmented rice. This study confirms that the lack of essential micronutrients in rice and the health risk associated with rice diets should remain a concern.

Optimizing green approach to enhanced antioxidants from Thai pigmented rice bran using deep eutectic solvent-based ultrasonic-assisted extraction.

Deep eutectic solvents (DES) have garnered significant attention as extraction media owing to their commendable attributes of being environmentally sustainable and the inherent adaptability of DES's versatile physical and chemical characteristics. The present study investigated the effects of deep eutectic solvents on the total contents of anthocyanin, phenolic, and flavonoids, as well as the antioxidant activity of Thai pigmented rice bran extract. The optimal extraction parameters for deep eutectic solvent-based ultrasonic-assisted extraction (DES-UAE) were also determined using the response surface methodology (RSM). The optimal conditions for the extraction of anthocyanins and other antioxidants from pigmented rice bran using a deep eutectic solvent were choline chloride: ethylene glycol (Ch:Eg) at a 1:2 ratio, mixed with 20 % water as a solvent. The ultrasonic-assisted extraction (UAE) at 37 kHz of frequency, 50 °C of temperature, 40 min of extraction time, and a 1:6 g/mL of solid-to-solvent ratio yielded a total anthocyanin content of 4.55 ± 0.09 mg C3G/g DW, a total phenolic content of 26.49 ± 0.62 mg GAE/g DW, a total flavonoid content of 6.57 ± 0.55 mg QE/g DW, and a percent inhibition of DPPH radical of 77.83 ± 1.51. By comparing the antioxidant content that was extracted from three cultivars of pigmented rice, it was found that Leum Pua black rice bran provided significantly higher antioxidant content compared to Hom Nin purple rice bran and Mali Dang red rice bran. This research suggests an achievable, eco-friendly, and effective method for preparing high-quality, consumer-safe Thai rice bran as a raw material for nutraceuticals.