Purple Rice Varieties Research Articles

Comparison of Metabolites and Main Nutritional Components between Uncooked and Cooked Purple Rice.

Cooking can lead to varying degrees of nutrient loss in purple rice. For this investigation, two varieties of purple rice (YZN1 and YZ6) were chosen as the focal points to explore the metabolites associated with rice nutrition post cooking using nontargeted and targeted metabolomics techniques. The results showed that after cooking the two purple rice varieties, the contents of the flavonoids; OPC; TP; total antioxidant capacity; and K, Na, Fe, Mn, Zn, Cu, Ca, and Mg significantly decreased. Compared with YZN1U (YZN1 uncooked), the amino acid and mineral element contents in YZN1C (YZN1 cooked) decreased to varying degrees. After cooking YZ6, the contents of seven amino acids significantly decreased. Following the preparation of purple rice, the metabolites primarily engaged in the pathways of flavonoid synthesis and flavone and flavonol synthesis. Flavonoids, total antioxidant capacity, mineral elements, and amino acids showed a strong correlation with delphinidin and luteolin. The ROC analysis demonstrated that the value of the area under the curve for delphinidin and luteolin was 1 when comparing YZ6C (YZ6 cooked) and YZ6U (YZ6 uncooked), as well as YZN1C and YZN1U. Delphinidin and luteolin can be used as potential biomarkers of nutrient loss after cooking purple rice. This study holds significant implications for the balanced nutrition and healthy development of human dietary grains.

Genotypic Variation of Purple Rice in Response to Shading in Yield, Anthocyanin Content, and Gene Expression.

Purple rice (Oryza sativa L.) contains anthocyanin, which acts as an antioxidant and functional food for humans. The levels of anthocyanin growth and production in rice are mainly controlled by the availability of light. However, shade can affect anthocyanin biosynthesis genes. Therefore, the objective of this study was to determine the yield and anthocyanin content among four purple rice varieties, which provide the difference in colors of purple and green leaves. This study also evaluated gene expression affected by shading treatment to understand the relation of grain anthocyanin and expression level. This research was conducted using a split plot design using four levels of shading (levels of shading from anthesis to maturity) with three replications, no shading, 30% shading, 50% shading, and 70% shading, as the main plots and purple rice varieties as subplots, KJ CMU-107, K2, K4, and KDK10, from anthesis to maturity. Shading significantly decreased yield and yield components, but increased grain anthocyanin content. Nonetheless, the response of yield and grain anthocyanin content to shading did not show a significant different between purple and green leaf varieties. In addition, the level of OsDFR gene expression was different depending on the shading level in four rice varieties. The OsDFR gene presented the highest expression at shading levels of 30% for K4 and 50% for KDK10, while the expression of the OsDFR gene was not detected in the purple rice varieties with green leaves (KJ CMU-107 and K2). The response of grain anthocyanin and gene expression of OsDFR to light treatment did not show significantly differences between the purple and green leaf varieties, suggesting that the appearance of anthocyanin in leaves might be not related to anthocyanin synthesis in the grain. Taken together, the results suggest that some purple rice varieties were more suitable for planting under low light intensity based on a lower level of grain yield loss, strong shade tolerance, and high anthocyanin content in leaf and grain pericarp. However, it is necessary to explore the effects of light intensity on genes and intermediates in the anthocyanin synthesis pathway for further study.

Metabolites Associated with the Main Nutrients in Two Varieties of Purple Rice Processed to Polished Rice.

Under the same nitrogen fertilizer and cultivation conditions, the nutrients of rice are strongly affected during the processing of brown rice to polished rice, especially in special rice varieties. In this study, twenty-two amino acids in brown and polished rice of two purple rice varieties were quantified using targeted metabolomics, and the relationships among the main nutrients, mineral elements and metabolites were analysed. The results showed that the amino acid levels in YZN1_H (polished rice of Yangzinuo No. 1) and YZN2_H (polished rice of Yangzinuo No. 2) decreased to different degrees compared with those in YZN1_B (brown rice of Yangzinuo No. 1) and YZN2_B (brown rice of Yangzinuo No. 2). Citric acid is closely associated with amino acids. The total sugar (TS), ATP, and soluble dietary fiber (SDF) levels in YZN1_B decreased by 9.37%, 53.85%, and 75.71%, respectively, compared with those in YZN1_H. The TS, ATP, and SDF levels in YZN2_B decreased significantly by 6.92%, 21.03%, and 76.78%, respectively, compared with those in YZN2_H. Citric acid was significantly negatively correlated with ATP and SDF but significantly positively correlated with carotenoids. The Se content in YZN1_H was significantly higher than that in YZN1_B by 87.02%. The Se content in YZN2_H was significantly higher than that in YZN2_B by 72.02%. Citric acid was significantly positively correlated with Fe, Mn, Ca, and Mg. Citric acid was identified as a candidate key metabolite that affects changes in the main nutrients in purple rice during processing.

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.

Responses of purple rice variety to light intensities and soil zinc application on plant growth, yield and bioactive compounds synthesis

Low light intensity restricts rice productivity, however, no deep information is evaluated on purple rice production and its bioactive compound. This study investigated the effects of light intensity on plant growth, yield, and bioactive compounds synthesis during the vegetative (experiment 1) and reproductive (experiment 2) stages of purple rice varieties grown with and without zinc fertilizer application. At the seedling stage in experiment 1, low and intermediate light intensities significantly decreased the total dry weight by 31% and 63%, respectively, compared with the full light intensity. The lower light intensity also decreased the concentrations of seedling total anthocyanin by 81% and total phenol by 36% compared to the full light intensity. At the reproductive stage in experiment 2, shading at early and seed development stages decreased grain yield by 15% compared to the unshaded grains. The concentrations of total anthocyanin and total phenol, DPPH activity, and anthocyanin compounds were increased by shading, while phenolic acid and flavonoid compounds were fluctuated depending on the compound species. Applying soil zinc fertilizer produced no significant improvement in productivity or bioactive compounds but did increase grain zinc concentration by from 6% to 13% compared to zero zinc application. These results will be useful for improving grain yield and quality in purple rice cultivation during the rainy season.

Optimizing anthocyanins extraction and the effect of cold plasma treatment on the anti‐aging potential of purple glutinous rice (Oryza sativa L.) extract

AbstractBackground and objectivesThe pericarp of color rice is a rich source of anthocyanins conferring several health benefits. The present study aimed to systemically optimize anthocyanins extraction from Thai purple glutinous rice and to elucidate the effect of cold plasma on the anti‐aging effect of the extract.FindingsAntioxidant effects and phytochemical constituents of the extracts from three Thai purple glutinous rice varieties including Doi Saket, Phayao, and Luem Pua were elucidated. Cyanidin‐3‐O‐glucoside (CNG) was a major compound in all varieties. Besides, Luem Pua rice extract presented the strongest antioxidation owing to its highest total phenolic and CNG contents. The optimized method for extracting CNG, which was proceeded by 2‐level full factorial design, used deionized (DI) water with pH 2.0 and temperature 150°C. Moreover, the cold plasma‐treated Luem Pua rice offered a five‐fold higher amount of CNG compared to the untreated sample with a significantly stronger anti‐aging potential.ConclusionsOur study provided the optimized method for CNG extraction from purple rice. Additionally, cold plasma potentially enhanced the anti‐aging property of the extract.Significance and noveltyThe contributions of the extracting factors on antioxidation and anthocyanins content were statistically elucidated, and the novel performance of cold plasma on biological properties of the plant materials was demonstrated.

Improving nutritional values in purple rice through germination and parboiling processes

The objective of this study was to determine the effects of seed germination and the parboiling process at different temperatures and times on total anthocyanin concentration, antioxidant activity, γ-aminobutyric acid (GABA), and the concentration levels of zinc (Zn) and iron (Fe) in the purple rice variety CMU 107. Germinated parboiled rice (GPR) and non-germinated parboiled rice (NPR) samples were parboiled by being soaked under specific conditions involving a series of temperatures (25°C, 60°C, and 80°C) and times (2, 4, and 6 hr) then being analyzed for the nutritional values. The results showed that the total anthocyanin concentration levels in NPR were about 62.2% higher than those in GPR; however, the antioxidant activity, Zn and GABA concentration levels in GPR were 197.9%, 9.8%, and 5.8% higher than in NPR, respectively. The soaking temperatures and times did not significantly affect the Fe concentrations in all treatments. Practical applications The process of germination following by parboiling at the appropriate soaking temperature and time could be an effective approach to improve antioxidant capacity, grain Zn, and GABA concentration in purple rice. The successful approach would be applied to use in the individual household and/or scaling up into the industrial units and consequently improve nutritional intake among rice consumers. However, anthocyanin concentration in germinated parboiled grain should be preserved carefully by selecting a specific method.

Stabilizing Grain Yield and Nutrition Quality in Purple Rice Varieties by Management of Planting Elevation and Storage Conditions

Purple rice has become an interesting source of nutritional value among healthy cereal grains. The appropriate cultivation together with post-harvest management would directly benefit farmers and consumers. This study aimed (i) to determine the yield, grain nutritional quality, and antioxidant capacity of purple rice varieties grown at lowland and highland elevations, and (ii) to evaluate the effects of storage conditions on the stability of the rice nutritional value during six months of storage. The high anthocyanin PES variety grown in the lowlands had a higher grain yield than the plants grown in the highlands, but grain anthocyanin concentration had the opposite pattern. In the high antioxidant capacity KAK variety, grain yield and DPPH activity were not significantly different between plants grown at the two elevations. The storage of brown rice and vacuum-sealed packages were both found to preserve greater anthocyanin concentrations in PES, but there was no effect on the DPPH activity of KAK. The grain properties were not significantly different between storage at 4 °C and room temperature. This study suggests that the optimal cultivation practices and storage conditions would result in the higher yield and grain quality of purple rice varieties.

Variation in nutritional quality of pigmented rice varieties under different water regimes

ABSTRACT This study evaluated grain anthocyanin, zinc (Zn) and iron (Fe) concentrations, and grain yield of eleven purple rice varieties (PP1–PP11) grown under wetland (W+) and aerobic conditions (W0) in 2 years. There was a significant variation in the concentrations of anthocyanin, Zn and Fe, by water regime and year among the varieties with a wide range of anthocyanin (1–117 mg 100 g−1) and narrower ranges of Zn (19–41 mg kg−1) and Fe (6–19 mg kg−1) concentrations. The nutritional quality in aerobic grown rice was lower than wetland grown among the varieties with higher levels of anthocyanin (>40 mg 100 g−1), Zn (>30 mg kg−1) and Fe (>15 mg kg−1), with smaller effects of water among varieties in the lower quality ranges. The lowering of anthocyanin in aerobic grown rice was observed in the two varieties of the upland ecotype that were highest in anthocyanin concentration, as well as some wetland varieties. The grain yield (1.4–6.7 Mg ha−1) was associated negatively with grain Zn concentration (r = −0.50, P ≤ 0.001), but not with grain Fe (r = −0.14, NS0.05) or anthocyanin (r = −0.27, NS0.05). The anthocyanin concentration in the purple rice increased with Zn concentration (r = 0.57, P ≤ 0.001). Wetland condition was shown to be more favorable than aerobic culture for intense pigmentation in the production of purple rice, as well as higher Zn and Fe concentrations.

Research Status and Genetic Improvement of Important Characters in Purple Rice

Rice (Oryza sativa L.) is one of the most important food crops in the world. Purple rice, as a special rice with important nutritional and health functions, has important scientific significance and application value for genetic improvement of purple rice and breeding of new varieties through in-depth study on its agronomic and related quality traits and products processed, and analysis of its genetic basis. In this paper, the new progress of purple rice in agronomic traits, quality traits, environmental impacts on purple rice and genetic basis of purple rice seed coat in recent years were reviewed and analyzed, and the application prospects of purple rice processing products and purple gene in rice genetic improvement were also prospected. Thus, our results will provide important information and reference for breeding new purple rice varieties with good quality and high yield.

The influence of starch structure and anthocyanin content on the digestibility of Thai pigmented rice

Starch digestibility and polyphenol content were investigated in six (white, red and purple) Thai rice varieties. Total phenolic content (TPC), total anthocyanin content (TAC), amylose content, gelatinization parameters and in vitro digestibility were determined. Purple and red rice varieties were found to have the highest levels of TPC, TAC and amylose content. TAC was not detected in white rice, while purple rice had the highest values. Gelatinization parameters were determined using differential scanning calorimetry. Red rice (Sung Yod) showed the highest gelatinization enthalpy. Non-pigmented rice (Hom Mali) in both purified starch and flour showed the highest starch digestibility, with a total starch digestibility of 76.85% and a digestion rate of 0.25 min−1. In contrast pigmented rice varieties showed lower starch digestibility. These results suggest that pigmented rice varieties are a source of phenolics and anthocyanin and also a possible good source of low digestible starch to develop as functional food products.

Farmers Drive Genetic Diversity of Thai Purple Rice (Oryza sativa L.) Landraces

Purple or black rice (Oryza sativa L.) is a culturally important germplasm in Asia with a long history of cultivation in northern Thailand. Purple rice is identified by the color of the rice pericarp, which varies from purple to black with the accumulation of phenolic acids, flavonoids, and anthocyanins. In the present study, we assessed molecular variation within and between wetland purple rice landraces germplasm from northern and northeastern Thailand using 12 microsatellite loci. All purple rice varieties surveyed showed high levels of homozygosity within varieties and strong genetic differentiation among varieties, indicating the fixation of genetic differences among them. This pattern is consistent with purple rice farming practices in northern Thailand, where a small portion of harvested seed is selected and replanted based on farmers’ preferences. The reduced genetic diversity and high homozygosity observed for purple rice is also consistent with patterns expected for this inbreeding crop. Genetic differentiation among the varieties showed some degree of structuring based on their geographical origin. Taken together, these data highlight that the genetic diversity and structure of wetland purple rice landraces is shaped by farmer utilization and cultivation through local cultural practices, and that conservation should focus on ex situ conservation across its cultivation range, along with on-farm, in situ conservation based on farmers’ seed-saving practices. In situ conservation may prove especially valuable for preserving the genetic identity of local varieties and promote adaptation to local environments.

Polyphenols from Australian-grown pigmented red and purple rice inhibit adipocyte differentiation

Coloured rice is rich in polyphenols and has been shown to have significant antioxidant and anti-adipogenic potential. The study aimed to investigate the anti-adipogenic properties of polyphenol extract (PE) derived from Australian-grown rice varieties. Eight wholegrain pigmented rice varieties were screened for their polyphenol content and antioxidant activity, of which, Yunlu29 (red), Purple (purple) and Reiziq (brown) had the highest values. The selected varieties were then subjected to in-vitro investigation to determine the effect of rice-derived PE on adipocyte differentiation. Lipid accumulation and peroxisome proliferator-activated receptor gamma (PPARγ) expression were quantified by oil red O staining and RT-PCR respectively. PE from Yunlu29 (red) and Purple rice varieties significantly reduced (p < 0.001) lipid accumulation by 53% and 56% respectively and PPARγ expression in adipocytes by 61.2% and 35.6% respectively. PE from Reiziq (brown), did not inhibit lipid accumulation in adipocytes however, did reduce PPARγ expression (p < 0.001).

紫黒米(黒米)モチ品種「きたのむらさき」と新育成ウルチ品種「TMK^*」の育成

紫黒米(黒米)モチ品種「きたのむらさき」と新育成ウルチ品種「TMK^*」の育成

紫黒米(黒米)新育成ウルチ品種「TMK^*」の発芽について

紫黒米(黒米)新育成ウルチ品種「TMK^*」の発芽について

Antioxidant properties and production of monacolin k, citrinin, and red pigments during solid state fermentation of purple rice (Oryzae sativa) varieties by Monascus purpureus

This study aims to evaluate the effects of various purple rice varieties on the production of monacolin K, citrinin, and red pigments by Monascus purpureus CMU002U (UV-mutant strain) and their antioxidant properties. The lowest value of citrinin concentration (132 ppb) was found in the SSF of the Na variety, which passed the standards of Japan, Taiwan, and European Union. The high monacolin K (13 482 ppm) and red pigment (388.25 units/g) levels were obtained from the fermented Doi Muser variety. The lowest IC&lt;sub&gt;50 &lt;/sub&gt;value of the DPPH assay was found in the extract of fermented Doi Saked variety. An investigation of temperature shifting of the SSF for the Doi Muser variety indicated that the incubation at 30°C for 5 days, followed by 25°C until 30 days, yielded the highest value of monacolin K (35 292 ppm) production. These results demonstrated that fermented purple rice has a high potential to be developed as a new food supplement.

English

English

Hull extracts from pigmented rice exert antioxidant effects associated with total flavonoid contents and induce apoptosis in human cancer cells

Residues from pigmented rice are attractive sources of active materials for human health. Methanol extracts from Ilpum (light-brown), Heugjinju (black), Jeogjinju (red), and WD-3 (purple) rice varieties were prepared and examined for antioxidant and anti-cancer activities. Bran and hull extracts from pigmented rice showed significantly (p<0.05) higher phenolic and flavonoidic compound contents, DPPH radical scavenging activities, and reducing powers than Ilpum extracts. Hull extracts showed greater cytotoxicity in human breast, melanoma, and oral cancer cells than bran extracts, where Heugjinju hull extract was the most potent. Hull extract-mediated cytotoxicity was due to apoptosis, based on the appearance of cellular shrinkage, DNA fragmentation, and nuclear condensation. The caspase-dependent and mitochondrial-mediated pathways were associated with hull extract-induced apoptosis in MCF-7 cells. Rice residues can be used as sources of phenolic antioxidants and as anti-cancer agents for human health.

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

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

Bioactive Compound Contents in Germinated Unpolished Purple Glutinous Rice from Kum Doi Saket and Kum Phayao Varieties

This research studied the bioactive compounds in unpolished purple glutinous rice and germinated unpolished purple rice produced from two rice varieties: Kum Doi Saket and Kum Phayao. Unpolished purple glutinous rice grains were produced by grain dehusking without polishing. The quality of their physical, chemical and bioactive compounds was analyzed. Kum Doi Saket unpolished purple glutinous rice had a statistically significant (p<0.05) higher amount of almost all compositions than Kum Phayao, except ash and reducing sugar content. Germinated unpolished purple rice was produced by soaking in water at 40°C for 3 hrs, and then incubating at 35°C. The GABA content at 40 hrs of germination had the maximum amount in both varieties and tended to decrease after this time. Thus, 40 hrs of germination time was the optimum period for germinated rice from both rice varieties. When compared before and after the 40-hr germination period, gamma-oryzanol increased, but total anthocyanins and antioxidant activity decreased slightly. Comparing the two varieties of germinated unpolished purple glutinous rice grains, Kum Doi Saket had a statistically significant (p<0.05) higher amount of bioactive compounds and antioxidant activity than Kum Phayao. Germinated unpolished purple glutinous rice provided from Kum Doi Saket had 16.31±0.34 mg/100g of GABA, 30.48±1.61mg/100g of gamma-oryzanol, 70.10±0.45 mg/100g of total anthocy- anins and 83.10±0.95% of antioxidant activity. This study has shown that the glutinous purple rice variety Kum Doi Saket had the highest potential for future development as a health food.