Srisawat Umarat, Panunto Watcharin, Kaendee Noppamat, Tanuchit Sermkiat, Itharat Arunporn, Lerdvuthisopon Nusiri, Hansakul Pintusomrn
Department of Preclinical Science, Faculty of Medicine, Thammasat University, Rangsit Campus, KlongLuang, Pathumthani, Thailand.
J Med Assoc Thai. 2010 Dec;93 Suppl 7:S83-91. doi: 10.1055/s-0030-1264431.
Free radical-induced oxidative stress damages cellular components leading to many human diseases. Plant-derived antioxidant compounds have become a profitable alternative to prevent oxidative stress in cells.
To determine and compare total phenolic and flavonoid contents as well as antioxidant activity using both chemical and cell assays in the water extracts of brown rice and rice bran from two Thai rice cultivars: Sangyod, a red pigmented rice typically grown in Southern Thailand and Dawk Mali 105, a commercial white-colored rice.
All the rice water extracts were analyzed for their total phenolic and flavonoid contents using the colorimetric assays, as well as for their antioxidant activity through two chemical assays: DPPH radical-scavenging and inhibition of lipid peroxidation assays, as well as through cell-based assays: scavenging capacity of intracellular ROS in HL60 cells using the fluorescent DCF and the NBT reduction.
The two chemical assays detected free radical scavenging and free radical chain breaking activities in all the rice extracts with EC50 values ranging from 26 to 357 microg/ml. Moreover, the cell-based assays detected ROS scavenging activities of these extracts with EC50 values in the range of 0.6-5 mg/ml. All these assays indicated that the water extracts of Sangyod exerted significantly higher antioxidant activity than those of Dawk Mali 105, which exhibited only moderate to low activity. Furthermore, high levels of antioxidant activity of the water extracts of Sangyod were closely correlated to their flavonoid and phenolic contents, which were approximately 2.5 and 3 times higher, respectively, than those of Dawk Mali 105.
These findings suggest that water extracts from colored brown rice or colored rice bran can be promising sources of potential natural antioxidants.
自由基诱导的氧化应激会损害细胞成分，从而引发多种人类疾病。植物来源的抗氧化化合物已成为预防细胞氧化应激的一种有益替代物。
使用化学和细胞检测方法，测定并比较泰国两个水稻品种糙米和米糠水提取物中的总酚和黄酮含量以及抗氧化活性。这两个品种分别是：桑约德，一种典型生长于泰国南部的红色素米；以及道克·马里105，一种商业白米。
所有水稻水提取物均采用比色法分析其总酚和黄酮含量，并通过两种化学检测方法（DPPH自由基清除和脂质过氧化抑制检测）以及基于细胞的检测方法（使用荧光DCF和NBT还原法检测HL60细胞内活性氧的清除能力）分析其抗氧化活性。
两种化学检测方法均检测到所有水稻提取物中的自由基清除和自由基链断裂活性，其半数有效浓度（EC50）值在26至357微克/毫升之间。此外，基于细胞的检测方法检测到这些提取物的活性氧清除活性，其EC50值在0.6至5毫克/毫升范围内。所有这些检测均表明，桑约德的水提取物抗氧化活性明显高于道克·马里105，后者仅表现出中度至低度活性。此外，桑约德水提取物的高抗氧化活性与其黄酮和酚类含量密切相关，其含量分别比道克·马里105高出约2.5倍和3倍。
这些发现表明，有色糙米或有色米糠的水提取物有望成为潜在天然抗氧化剂的来源。
