홍국쌀 추출물의 항산화 작용을 DPPH radical 및 hydroxyl radical 소거능, 간암 세포에서의 산화적 DNA 손상과 항산화 효소의 유전자 발현에 미치는 영향으로 분석하였다. 홍국쌀 추출물의 DPPH radical 소거능은 ethyl acetate 추출물, methanol 추출물, butanol 추출물 순이었으며, ethyl acetate 추출물의 DPPH radical 소거능은 0.2 mg/mL에서 85%, IC<SUB>50</SUB>는 0.13 mg/mL로 나타났다. Ethyl acetate 추출물의 hydroxyl radical 소거능을 DCF fluorescence로 측정한 결과, cuvette에서는 2.5 μg/mL에서 44.2%, 5.0 μg/mL 74.1%, 10.0 μg/mL >100%로 나타났고, HepG<SUB>2</SUB> cell에서는 ethyl acetate 추출물로 전처리한 세포의 radical이 H<SUB>2</SUB>O<SUB>2</SUB>로만 처리한 세포에 비해 유의적으로 감소하였다. 홍국쌀 ethyl acetate로 전처리한 세포의 DNA 손상이 H<SUB>2</SUB>O<SUB>2</SUB>로만 처리한 세포에 비해 유의적으로 낮았으며, 추출물 대신 lovastatin을 처리한 세포는 DNA 손상이 증가하는 것으로 나타났다. 항산화 효소 유전자의 상대적 발현 정도를 측정한 결과, 산화 스트레스 없이 ethyl acetate 추출물로 전처리한 세포에서는 SOD와 GPx가 control에 비해 각각 3.25배, 2.67배 유의적으로 증가하였으며, 추출물로 전처리한 후 산화 스트레스에 노출시킨 세포에서는 CAT가 control에 비해 5 μg/mL에서 4.64배, 10 μg/mL에서 7.0배 유의적으로 증가하였다.
Red yeast rice (RER) has been used in China for centuries for its medicinal properties and is an increasingly popular alternative lipid-lowering treatment. This study was carried out to estimate the antioxidant properties of RER extracts. The ethyl acetate extract exhibited the DPPH radical scavenging activity of 85% at 0.2 mg/mL and IC<SUB>50</SUB> 0.13 mg/mL. A significant proportion of hydroxyl radicals in a cuvette were scavenged: 44.2% at 2.5 μg/mL, 74.1% at 5.0 μg/mL, and >100% at 10 μg/mL. The HepG<SUB>2</SUB> cells pre-treated with RER ethyl acetate extract reduced the hydroxyl radicals significantly compared to the control cells. Oxidative DNA damage was measured using a Comet assay. The RER ethyl acetate extract did not induce any DNA damage per se, and appeared to enhance the resistance to DNA damage caused by an oxidant challenge with H<SUB>2</SUB>O<SUB>2</SUB>, whereas lovastatin increased the level of DNA damage in the cells in both the unstressed (no oxidant) and those stressed with H<SUB>2</SUB>O<SUB>2</SUB>. The relative gene expression of the antioxidant enzymes in HepG<SUB>2</SUB> cells were also affected by the RER ethyl acetate extract. The HepG<SUB>2</SUB> cells were pre-incubated with the RER ethyl acetate extract, and then stressed with H<SUB>2</SUB>O<SUB>2</SUB> or left unstressed (no oxidant). In the unstressed cells, superoxide dismutase (Cu/Zn SOD) and glutathione peroxidase (GPx) were increased significantly 3.25-fold and 2.67-fold, respectively, whereas in the stressed cells, the catalase (CAT) level was increased by 4.64-fold and 7.0-fold at 5 μg/mL and 10 μg/mL, respectively, compared to those of the control. From these results, RER appears to be effective in suppressing oxidative stress.