Phytochemical profiles and antioxidant capacity of pigmented and non-pigmented genotypes of rice (Oryza sativaL.)

Abstract

Pigmented rice (Oryza sativa L.) genotypes become increasingly important in the agroindustry due to their bioavailable compounds that have the ability to inhibit the formation and/or to reduce the effective concentration of reactive cell-damaging free radicals. This study aimed at determining the concentrations of free, and bound phytochemicals and their antioxidant potential (DPPH and ABTS assays) as well as the vitamin E and carotenoids contents of non-pigmented and pigmented rice genotypes. The results confirmed that the content of total phenolics and flavonoids contents, as well as the antioxidant capacity (DPPH and ABTS assays) of pigmented rice was several-fold greater than non-pigmented ones (4, 4, 3 and 5 times, respectively). Compounds in the free fraction of pigmented rice had higher antioxidant capacity relative to those in the bound form, whereas the non-pigmented rice cultivars exhibited the opposite trend. Ferulic acid was the main phenolic acid of all rice genotypes, whereas black rice contained protocatechuic and vanillic acids in higher contents than red rice and non-pigmented rice genotypes. For vitamin E (tocopherols and tocotrienols) and carotenoids (lutein, zeaxanthin and β-carotene) contents, no obvious concentration differences were observed between non-pigmented and pigmented rice, with the black rice exhibiting the highest carotenoid content. Overall, pigmented rice genotypes contain a remarkable amount of bioactive compounds with high antioxidant capacity; therefore, they have great potential as a source of bioactives for developing functional food products with improved health benefits.

The Genetic Basis and Nutritional Benefits of Pigmented Rice Grain

“…Rice grain represents a good source of vitamin E, including both the tocopherols and the tocotrienols (Zubair et al, 2012). The βand γ-tocotrienols are the most abundant forms present in rice (Irakli et al, 2016). According to Gunaratne et al (2013), red rice grains harbor higher levels of total tocopherol and tocotrienol than do the grains of modern white rice varieties.…”

“…In an alternative pathway, particularly active in black rice, cinnamic acid is converted to vanillic acid and protocatechuic acid (Zhang et al, 2015;Shao et al, 2018). In red rice, caffeic acid has been identified as a minor phenolic acid, while this compound is not detectable in brown rice (Gunaratne et al, 2013;Zhang et al, 2015;Irakli et al, 2016;Shao et al, 2018). Additional phenolic acids identified include syringic acid in the extract of brown, red, and black rice (Ghasemzadeh et al, 2018;Shao et al, 2018), pinellic acids in red and white rice (Kim et al, 2014), hydroxybenzoic acid in black rice extracts (Tantipaiboonwong et al, 2017), and gallic acid in the extracts of the red rice mutant AM-425 (Chiou et al, 2018).…”

Effect of olive pulp enrichment on physicochemical and antioxidant properties of wheat bread

“…Extraction was carried out at least in triplicate. The amount of TPC in extracts was determined according to the Folin-Ciocalteu method (Irakli, Samanidou, Katsantonis, Biliaderis, & Papadoyannis, 2016;Singleton, Orthofer, & Lamuela-Raventos, 1999). The results were expressed as mg of GA equivalents per 100 g of the dried sample (mg GAE/100 g dw).…”

“…The results were expressed as mg of GA equivalents per 100 g of the dried sample (mg GAE/100 g dw). The concentration of TFC was determined using the aluminum chloride colorimetric method (Bao, Cai, Sun, Wang, & Corke, 2005;Irakli et al, 2016). The TFC was estimated using a standard calibration curve, with catechin as a standard, and expressed as milligrams catechin equivalent (CATE) per 100 g of dry weight (mg CATE/100 g dw).…”

“…Results were expressed as mg Trolox equivalents per 100 g of dry sample (mg TE/100 g dw). The ferric reducing antioxidant power assay (FRAP) was performed according Benzie and Strain (1996) and Irakli et al (2016). The results were expressed as mg Trolox equivalents per 100 IJFS April 2020 Volume 9 pages 178-192 g of dry sample (mg TE/100 g dw).…”