Black rice

Abstract: The dye-sensitized solar cells (DSC) were assembled by using natural dyes extracted from black rice, capsicum, erythrina variegata flower, rosa xanthina, and kelp as sensitizers. The I SC from 1.142 mA to 0.225 mA, the V OC from 0.551 V to 0.412 V, the fill factor from 0.52 to 0.63, and P max from 58 μW to 327 μW were obtained from the DSC sensitized with natural dye extracts. In the extracts of natural fruit, leaves and flower chosen, the black rice extract performed the best photosensitized effect, which was due to the better interaction between the carbonyl and hydroxyl groups of anthocyanin molecule on black rice extract and the surface of TiO 2 porous film. The blue-shift of absorption wavelength of the black rice extract in ethanol solution on TiO 2 film and the blue-shift phenomenon from absorption spectrum to photoaction spectrum of DSC sensitized with black rice extract are discussed in the paper. Because of the simple preparation technique, widely available and low cheap cost natural dye as an alternative sensitizer for dye-sensitized solar cell is promising.

Abstract: Total phenolics, flavonoid contents and antioxidant capacity from a wide collection of rice germplasm were measured, and their relations to grain color, grain size and 100-grain weight were investigated. Highly significant genotypic differences were observed in total phenolics, flavonoid contents and 2,2-azino-bis-(3-ehylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) radical cation antioxidant capacity. They displayed an increasing order in the white rice, red rice and black rice, yet several white rice had higher phenolics and flavonoids contents than the red rice. Significant positive pair-wise correlations were found among the phenolics, flavonoid contents and antioxidant capacity, and the coefficient between the phenolic contents and antioxidant capacity was extremely high (r = 0.96). Among all rice accessions, the grain color parameters had negative correlations with the phenolics, flavonoid contents and antioxidant capacity (p < 0.001). The negative correlation between a* and antioxidant capacity, and the positive correlation between H° and antioxidant capacity were consistent within the respective white rice and red rice groups. Flavonoid contents had positive correlation with grain length and length to width ratio, and had negative correlation with the 100-grain weight among all rice accessions. It was also found that 100-grain weight still had negative correlations with phenolics, flavonoid contents and antioxidant capacity within the white rice genotypes. These relationships may serve as indexes to indirectly select breeding lines high in the phenolics, flavonoids and antioxidant capacity. Principal component analysis including the information for phenolics, flavonoids, antioxidant capacity, grain color parameters, grain size and 100-grain weight extracted five principal components that explained 83.7% of the total variances. The results of this study may provide new opportunities for rice breeders and eventually commercial rice growers to promote the production of rice with enhanced nutritional quality.

Abstract: Nine red and three black rice varieties from Thailand, China and Sri Lanka were analysed to determine their proximate composition and their physicochemical and antioxidant properties. Four groups of rice varieties with different amylose contents were identified. Cyanidin 3-glucoside and peonoidin 3-glucoside were confirmed as the dominant anthocyanins in black rice varieties with contents ranging from 19.4 to 140.8 mg/100 g DM and 11.1–12.8 mg/100 g DM, respectively. Total phenolic content (TPC) differed significantly between the varieties, but not between the colours. Highest TPC was found in the red Thai rice Bahng Gawk (BG) with 691 FA equivalent mg/100 g DM, which showed as well the highest antioxidant properties. In red varieties, the major phenolic acids in the free form were ferulic, protocatechuic and vanillic acid, whereas in black varieties protocatechuic acid was dominant followed by vanillic and ferulic acid. In the bound form, ferulic acid was predominant in both colours, where contents differed significantly, followed by p-coumaric and vanillic acid. The antioxidative capacity did not differ significantly between both colours but amongst genotypes. Antioxidant capacity of rice varieties ranged within 0.9–8.1 mmol Fe(II)/100 g DM for FRAP and 2.1–12.3 mmol TEAC/100 g DM. DPPH scavenging ability ranged from 13.0% to 76.4% remaining DPPH.

Abstract: 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.

Abstract: The objectives of this study were to determine antioxidant activity of the methanolic extracts from some grains and to investigate relationships between antioxidant activities and antioxidant contents in the extracts. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities, 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical cation scavenging activities, inhibitory effect on lipid peroxidation, chelating activity and reducing power have been used to investigate the relative antioxidant activities of the extracts from grains. The concentrations of total polyphenolics and carotenoids in the extracts were measured by spectrophotometric methods and vitamin E analysis was carried out by HPLC. The methanolic extracts prepared from red sorghum and black rice showed significantly higher antioxidant activities and contained higher polyphenolic contents than other grains such as white rice, brown rice, mungbean, foxtail millet, prosomillet, barley, and adlay. Polyphenolic compounds were the major naturally occurring antioxidants in grains. The correlation coefficient between total polyphenolic content and ABTS radical cation scavenging activity in the extracts was >0.99. However, no relationship was found between antioxidant activities and carotenoids and vitamin E derivatives.