College of Forestry, Northwest A&F University, 3 Taicheng Road, Yangling 712100, Shaanxi, China.
Molecules. 2013 Feb 1;18(2):1857-68. doi: 10.3390/molecules18021857.
Leaf of Eucommia ulmoides Oliver (EU) is a Traditional Chinese Medicine and a functional food in China. Antioxidant contents of EU leaves, which were collected monthly during the period of May-October in three years, were determined. Samples' antioxidant capacity was characterized by DPPH radical scavenging activity, hydroxyl radical scavenging activity, ferrous chelating ability, and antioxidant capacity in linoleic acid emulsion and in rapeseed oil assays. The results showed that contents of some active compounds and antioxidant activity were related to a certain time of the year. Samples collected in August showed high content of phenolics, and the samples collected in May contained higher amount of flavonoids than other samples. Leaves collected in May or June exhibited high contents of rutin, quercetin, geniposidic acid and aucubin. The August leaves showed stable and high DPPH radical scavenging activity, and ferrous chelating ability. May samples showed strong inhibitory effects on oxidation of rapeseed oil and linoleic acid. The DPPH radical scavenging activity was related to the total phenolics content. Flavonoids played an important role in the inhibitory effects on rapeseed oil and linoleic acid oxidation. Therefore, August and May were indicated as the best months to harvest EU leaves for industry.
杜仲叶是中国的一种传统中药和功能性食品。在三年间的 5 月至 10 月，每月采集杜仲叶样本，检测其抗氧化成分。采用 DPPH 自由基清除活性、羟基自由基清除活性、亚铁螯合能力以及在亚油酸乳液和菜籽油中的抗氧化能力等方法，评估样本的抗氧化能力。结果表明，某些活性化合物的含量和抗氧化活性与一年中的特定时间有关。8 月采集的样本中酚类物质含量较高，5 月采集的样本中黄酮类物质含量高于其他月份。5 月或 6 月采集的样本中芦丁、槲皮素、京尼平苷酸和桃叶珊瑚苷含量较高。8 月的叶子表现出稳定且较高的 DPPH 自由基清除活性和亚铁螯合能力。5 月的样本对菜籽油和亚油酸的氧化具有很强的抑制作用。DPPH 自由基清除活性与总酚含量有关。黄酮类物质对菜籽油和亚油酸氧化的抑制作用起着重要作用。因此，8 月和 5 月是杜仲叶工业收获的最佳月份。
