Protective effect of two Thai pigmented rice cultivars against H2O2-induced oxidative damage in HT-29 cell culture

Radicals derived from exogenous and endogenous sources are considered to be the principal cause of genetic damage. Exogenous and endogenous radicals participate in the reactive oxygen species (ROS) formation, which leads to damages in the DNA, RNA, proteins and lipids. However, dietary compounds, mainly from pigmented rice, are an essential source of antioxidants that help protect cells from damage. This study seeks to determine the antioxidant properties and cytoprotective effect of two Thai pigmented rice extracts namely the glutinous black rice (native name: Neaw dum moa37) and red rice (native name: Hom gradung-nga57) on H2O2-induced damage in HT-29 cells. The bioactive compound contents, as well as antioxidant activities of both rice extracts, were investigated. The protective effect of rice extracts on H2O2-induced damage was executed following the co-incubation method. HT-29 cells were exposed to H2O2 and different rice extract concentrations for 3 h and an MTT assay was used to measure the viability of the cell. The ROS level was determined using the 2′,7′-dichlorofluorescin diacetate (DCFDA). The result showed that glutinous black rice extract contained significantly higher contents of all analysed antioxidants and activities than red rice extract. Glutinous black rice showed a higher cytotoxic effect compared to red rice. At the non-toxic concentration of both rice extracts, the HT-29 cells were guarded against the H2O2 induced oxidative stress. Besides, the intracellular ROS accumulation result from H2O2 exposure was significantly reduced in the presence of rice extracts for both glutinous black rice and red rice compared to control. Hence, this study has demonstrated the potential properties of both pigmented rice extracts in alleviating H2O2-mediated damage in HT-29 cells.

Sensory evaluation and antimicrobial activity of snack bar from black soybean and black rice containing anthocyanins

Snack bars made from black soybean and black rice could be used as a food product to complement the energy and nutrients needs. Both have anthocyanins content in black soybean and black rice as well as the potential as an antimicrobial agent. The purpose of this study was to obtain an optimal formula, evaluate the sensory acceptance, analyze the total monomeric anthocyanin content of the snack bars, and compare the growth of probiotic and pathogenic bacteria in anthocyanins crude extracts from the snack bars. The production of snack bars was done by using three variations of main ingredients, including 30% of black soybean + 70% of black rice (formula 1), 50% of black soybean + 50% of black rice (formula 2), and 70% of black soybean + 30% of black rice (formula 3). The results performed that consumers acceptance for formulas 2 and 3 was not significantly different (P > 0.05), but significantly higher (P < 0.05) than formula 1. Total monomeric anthocyanin content analyzed by the pH differential method in these three snack bars formulas had no significant difference (P > 0.05). The growth analysis of probiotic and pathogenic bacteria showed that the percentage of growth inhibition of Escherichia coli and Salmonella enterica serovar Typhi bacteria was significantly higher (P = 0.00) compared to Lactobacillus acidophilus. Also, formulas 1 and 2 could significantly inhibit E. coli and S. enterica ser. Typhi bacteria (P = 0.00) compared to formula 3. It could be concluded that formula 2 showed the best snack bar based on sensory evaluation and pathogenic bacteria inhibition assay.

Evaluation of Phytochemical Contents and In Vitro Antioxidant, Anti-Inflammatory, and Anticancer Activities of Black Rice Leaf (Oryza sativa L.) Extract and Its Fractions

Black rice leaves (Oryza sativa L.) are a major part of rice straw left in open fields after rice harvest as agricultural waste. In this study, crude ethanolic extract (CEE) and various solvent fractions (hexane (Hex), ethyl acetate (EtOAc), n-butanol (n-BuOH), and aqueous fractions) of black rice leaves were investigated for their bioactive compound contents as well as antioxidant, anti-inflammatory, and anticancer activities. The results demonstrated that among all the fractions, the n-BuOH fraction presented the greatest contents of total phenolics and flavonoids, while anthocyanins were found to be abundant in the n-BuOH and aqueous fractions, which also exhibited powerful antioxidant abilities according to DPPH and ABTS radical-scavenging assays and a reducing power assay. Regarding anti-inflammatory activity, CEE and EtOAc reduced the production of NO and cytokine secretion (PGE2, IL-6, and IL-1β) but displayed less effect on tumor necrosis factor α (TNF-α) release in lipopolysaccharide (LPS)-induced RAW 264.7 cells. They also significantly decreased iNOS and COX-2 protein expression. Additionally, the phenolics-rich ethyl acetate fraction showed the greatest activity against HepG2 liver carcinoma cells, inhibited cell growth, increased the Sub-G1 population, and induced apoptosis via mitochondrion-dependent mechanisms. In conclusion, black rice leaves, a byproduct of rice, exhibited strong antioxidant, anti-inflammatory, and anticancer capacities and might be useful for application in functional foods and the pharmaceutical industry.