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.

Regulatory Effects of Thai Rice By-Product Extracts from Oryza sativa L. cv. Bue Bang 3 CMU and Bue Bang 4 CMU on Melanin Production, Nitric Oxide Secretion, and Steroid 5α-Reductase Inhibition.

Alopecia and gray hair are common hair abnormalities affecting physical appearance and causing psychological problems. Chemical treatments partially restore hair disorders but have distressing side effects. Bioactive plant compounds constitute promising sources of potential medicinal substances instead of chemical agents, producing high side effects. In this study, we focused on the waste of local rice cultivars: Bue Bang 3 CMU (BB3CMU) and Bue Bang 4 CMU (BB4CMU) from the north of Thailand. The rice bran oil (RBO), defatted rice bran extract (DFRB), and rice husk (H) were determined for in vitro hair revitalization in melanin production, nitric oxide (NO) secretion, and steroid 5α-reductase inhibition. The results indicated that BB4CMU-RBO with high contents of iron, zinc, and free fatty acids showed a comparable induction of melanin production on melanocytes (130.18 ± 9.13% of control) to the standard drug theophylline with no significant difference (p > 0.05). This promising melanin induction could be related to activating the NO secretion pathway, with the NO secretion level at 1.43 ± 0.05 µM. In addition, BB4CMU-RBO illustrated a significant inhibitory effect on both steroid 5α-reductase genes (SRD5A) type 1 and type 2, which relates to its primary source of tocopherols. Hence, rice bran oil from the Thai rice variety BB4CMU could be applied as a promising hair revitalizing candidate, from natural resources, to help promote hair growth and re-pigmentation effects.

Variation of Anthocyanin, Phenol, and Antioxidant Capacity in Straw among Rice Varieties and Growing Locations as a Potential Source of Natural Bioactive Compounds.

This study evaluated the variation in bioactive compounds (anthocyanins, phenols, and antioxidants) among 22 rice varieties in the same growing locations and among four varieties collected from eight different provinces in Northern Thailand. Wide variation in anthocyanins, phenols, and antioxidant capacity was established, ranging from 1.6 to 33.0 mg/100 g, 249.9 to 477.7 mg gallic acid/100 g, and 0 to 3,288.5 mg trolox equivalent/100 g, respectively. The highest straw anthocyanin and phenol concentrations were found in KDK (a traditional photoperiod-sensitive variety with purple pericarp and leaves) and K4 (an advanced, photoperiod-insensitive variety with purple pericarp and leaves), while the highest antioxidant capacity was found in KH CMU (an improved traditional photoperiod sensitive variety with a purple pericarp and green leaves) and K4. The variation of the bioactive compounds was also found in the same variety grown at different locations, e.g., the KDMl105 grown in Prayao province had a straw anthocyanin concentration higher than when grown in Mae Hong Son province. The effect was also observed in phenol content and antioxidant capacity when the same rice variety was grown across various locations. A significant correlation between total phenol and antioxidant capacity was observed across rice varieties and growing locations but was not found between anthocyanin and antioxidant capacity. This study found that the bioactive compounds in rice straw varied among rice varieties and growing locations. Straw phenol acts as a major antioxidant that can be used as a characteristic for the selection of rice varieties with high antioxidant capacity for use at the industrial scale for the processing of food, pharmaceuticals, and medicinal products.

The Potential of High-Anthocyanin Purple Rice as a Functional Ingredient in Human Health.

Purple rice is recognized as a source of natural anthocyanin compounds among health-conscious consumers who employ rice as their staple food. Anthocyanin is one of the major antioxidant compounds that protect against the reactive oxygen species (ROS) that cause cellular damage in plants and animals, including humans. The physiological role of anthocyanin in plants is not fully understood, but the benefits to human health are apparent against both chronic and non-chronic diseases. This review focuses on anthocyanin synthesis and accumulation in the whole plant of purple rice, from cultivation to the processed end products. The anthocyanin content in purple rice varies due to many factors, including genotype, cultivation, and management as well as post-harvest processing. The cultivation method strongly influences anthocyanin content in rice plants; water conditions, light quantity and quality, and available nutrients in the soil are important factors, while the low stability of anthocyanins means that they can be dramatically degraded under high-temperature conditions. The application of purple rice anthocyanins has been developed in both functional food and other purposes. To maximize the benefits of purple rice to human health, understanding the factors influencing anthocyanin synthesis and accumulation during the entire process from cultivation to product development can be a path for success.

Simultaneous Biofortification of Rice With Zinc, Iodine, Iron and Selenium Through Foliar Treatment of a Micronutrient Cocktail in Five Countries.

Widespread malnutrition of zinc (Zn), iodine (I), iron (Fe) and selenium (Se), known as hidden hunger, represents a predominant cause of several health complications in human populations where rice (Oryza sativa L.) is the major staple food. Therefore, increasing concentrations of these micronutrients in rice grain represents a sustainable solution to hidden hunger. This study aimed at enhancing concentration of Zn, I, Fe and Se in rice grains by agronomic biofortification. We evaluated effects of foliar application of Zn, I, Fe and Se on grain yield and grain concentration of these micronutrients in rice grown at 21 field sites during 2015 to 2017 in Brazil, China, India, Pakistan and Thailand. Experimental treatments were: (i) local control (LC); (ii) foliar Zn; (iii) foliar I; and (iv) foliar micronutrient cocktail (i.e., Zn + I + Fe + Se). Foliar-applied Zn, I, Fe or Se did not affect rice grain yield. However, brown rice Zn increased with foliar Zn and micronutrient cocktail treatments at all except three field sites. On average, brown rice Zn increased from 21.4 mg kg-1 to 28.1 mg kg-1 with the application of Zn alone and to 26.8 mg kg-1 with the micronutrient cocktail solution. Brown rice I showed particular enhancements and increased from 11 µg kg-1 to 204 µg kg-1 with the application of I alone and to 181 µg kg-1 with the cocktail. Grain Se also responded very positively to foliar spray of micronutrients and increased from 95 to 380 µg kg-1. By contrast, grain Fe was increased by the same cocktail spray at only two sites. There was no relationship between soil extractable concentrations of these micronutrients with their grain concentrations. The results demonstrate that irrespective of the rice cultivars used and the diverse soil conditions existing in five major rice-producing countries, the foliar application of the micronutrient cocktail solution was highly effective in increasing grain Zn, I and Se. Adoption of this agronomic practice in the target countries would contribute significantly to the daily micronutrient intake and alleviation of micronutrient malnutrition in human populations.