Effect of elevated carbon dioxide (CO₂) on phenolic acids, flavonoids, tocopherols, tocotrienols, gamma-oryzanol and antioxidant capacities of rice (Oryza sativa L.).

摘要

There have been no studies conducted with the objective of investigating the effect of elevated CO₂ concentrations ([CO₂]) on antioxidants in grains. Therefore, a two-year field experiment was conducted using open-top chambers with two levels of atmospheric CO₂ (375 and 550 mumol/mol) to evaluate their effects on rice grain antioxidants. Following exposure to high [CO₂], the total phenolic content of all rice milling fractions decreased (3%-18%), with the highest reduction in the brown rice for sinapic acid (167%), and in the white rice for p-hydroxybenzoic acid (100%). The total flavonoid content also decreased under elevated [CO₂] in all rice milling fractions (8%-14%), with apigenin (25%) being highly affected in the white rice, and tricin (12%) in the bran. The same trend was found for gamma-oryzanol, with decreases of 35%, 32%, 25%, and 2% in the white rice, brown rice, husk, and bran, respectively. In the white and brown rices, tocopherols and tocotrienols were all lower under elevated [CO₂], with reductions larger for alpha-tocotrienol (69%), gamma-tocotrienol (46%), and alpha-tocopherol (38%). Good correlations between antioxidant contents and DPPH radical scavenging capacities indicated that these decreases may be meaningful in the preventive ability of rice against free radical-mediated degenerative diseases