Antioxidant Activity of Commercial Wild Rice and Identification of Flavonoid Compounds in Active Fractions

Abstract

The health benefits of whole grain consumption have been attributed to their content of complex carbohydrates, vitamins, minerals, and other phytochemical constituents. Wild rice is a whole grain finding applications in gourmet foods due to its nutritional value and unique taste. However, little is known about its antioxidant properties and phytochemical components. The objectives of this study were to evaluate the antioxidant properties of wild rice. Eleven commercial wild rice samples (raw, mixed, and processed) were extracted with acetone and fractionated using a Sephadex LH-20 column. 2,2-Diphenyl-1-picrylhydrazyl radical (DPPH(*)) scavenging activity, oxygen radical absorbance capacity (ORAC), and total phenolic content were evaluated to determine the antioxidant properties of wild rice. The antioxidant activity of wild rice was found to be 30 times greater than that of the control white rice. Significant differences (p < 0.05) in antioxidant activities were found among raw, mixed, and processed samples. For raw samples, DPPH(*) radical scavenging activities and ORAC values ranged from 611 to 917 micromol of Trolox equivalent (TE)/100 g and from 4069 to 6064 micromol of TE/100 g, respectively. For mixed and processed wild rice, DPPH(*) radical scavenging activities were 373 and 441 micromol of TE/100 g, respectively. The corresponding ORAC values were 2284 and 2557 micromol of TE/100 g. Total phenolic content (TPC) of raw wild rice varied from 2472 to 4072 mg of ferulic acid equivalent (FAE)/kg, higher than that of the mixed sample (1460 mg of FAE/kg) and processed sample (2076 mg of FAE/kg). TPC was highly correlated with total antioxidant activity of wild rice (r = 0.92). Tandem mass spectrometric techniques revealed the antioxidants identified in wild rice to be flavonoid glycosides (diglucosyl apigenin, glucosyl-arabinosyl apigenin, and diarabinosyl apigenin) in factions 2 and 3 and flavan-3-ols (catechin, epicatechin, and oligomeric procyanidin) in fractions 4 and 5.

Polyphenols in whole rice grain: Genetic diversity and health benefits

“…B-type proanthocyanidin is very common in nature. In red rice, the block unit of proanthocyanidin consists of catechin and epicatechin (Gunaratne et al, 2013;Qiu, Liu, & Beta, 2009), and exists in B-type (Fig. 1c).…”

“…From pH 3 to 6, anthocyanins change into colorless carbinol pseudobase or chalcone, while in neutral and slightly acidic pH, they turn into neutral quinonoidal bases showing purple to violet color (He & Giusti, 2010). For proanthocyanidins, organic solvent has been used as extractant, such as 80% methanol, acetic acid acidified acetone (Gunaratne et al, 2013;Min et al, 2012;Qiu et al, 2009).…”

“…In red rice, hexamer is the most abundant which accounts for about 16.9% for the total polymers, followed by heptamer, pentamer, and octamer which account for 10.1%, 9.7%, and 9.6%, respectively, and monomer is the lowest which account for only 0.4% (Min et al, 2012). In a different species of wild rice, the content of polymers was dramatically different; some varieties only had monomers and trace amount of dimers whereas some varieties had extremely high contents of trimers or pentamers (Qiu et al, 2009). Interestingly, a few black rice have both anthocyanins and proanthocyanins with the total content of 2050 and 153.1 lg/g, respectively (Finocchiaro, Ferrari, & Gianinetti, 2010).…”

Karakterisasi Kimia dan Efek Hipoglikemik Beras Analog Berbahan Dasar Jagung, Sorgum, dan Sagu Aren

“…Pengukuran kadar total fenolik kedua beras analog disajikan pada Tabel 1. Total phenolics beras analog A (0,10 ± 0,00 mg GAE/g sampel) dan beras analog B (0,16 ± 0,00 mg GAE/g sampel), sudah lebih tinggi dibandingkan dengan total fenol beras putih yaitu 0,044 mg GAE/g sampel (Qiu, 2009). Hal ini dapat disebabkan oleh penggunaan bahan baku jagung dan sorgum yang mengandung kadar fenolik cukup tinggi yaitu 2,607-3,201 mg GAE/g sampel (De la Parra dkk., 2007) dan 1,44 mg/GAE/g (Moraes dkk., 2015), masing-masing.…”

Inhibitory Effect of Apigenin on Pharmacokinetics of Venlafaxine in vivo and in vitro

“…It has been demonstrated that apigenin is the main active ingredient in the flower of Chrysanthemum morifolium extract, a widely used traditional Chinese medicine component [6]. Apigenin, in particular, has been highlighted in the recent researches, because of their potential role as the contributing factors to the antioxidant activity, anticarcinogenic activity, hypertension prevention substance and antibacterial qualities [7,8,9]. And apigenin worked fairly well to calm the agitated.…”