白茅根化學成分及生物活性之研究

白茅 (Imperata cylindrica) 為禾本科 (Gramineae) 多年生根莖類植物。白茅的根部是一種常見的中國藥材，自古常用來治療血熱引起的出血、鼻出血及血尿。而在現今的研究中被發現具有抗癌、抗痛風及降血糖的活性。本研究中，乾燥的白茅根部以甲醇浸泡，其中甲醇粗萃物經由分配萃取法得到乙酸乙酯層萃取物、正丁醇層萃取物以及水層萃取物。在初期的抗氧化實驗結果中，乙酸乙酯層萃取物具有活性，因此，將乙酸乙酯層經由管柱層析分離出三十六組分液，並再利用管柱層析、高效液相層析與再結晶等方法進行分離純化。經由質譜與核磁共振光譜分析並進行文獻比對，目前共鑑定出二十九個化合物，包含四個三萜類 (Triterpenoids)、四個固醇類 (Steroids)、七個蒽醌類 (Anthraquinones)、六個芳香類 (Aromatics)、兩個類黃酮 (Flavonoids)、一個香豆素(coumarin)、一個色酮類 (Chromone)、兩個苯酞類 (phthalides)、一個氧蒽酮類 (xanthone) 和一個有機酸類 (organic acid)。其中， Isoscopoletin為天然物界首次發現的化合物。在抗氧化活性方面，Protocatechuic acid、Syringic acid 和 Catenarin具自由基清除活性，其 IC50分別為 9.34±2.14、9.90±1.57 以及 24.05±2.41μg/mL。而在黃嘌呤氧化酶抑制試驗中，4-hydroxybenzaldehyde 的活性最佳，其 IC50 為 8.63±0.10 μg/mL。血管收縮素轉換酶抑制試驗方面，Protocatechuic acid、Syringic acid 和 Methyl hydrogen fumarate 的 IC50分別為 13.42±0.25、12.26±0.47 及 10.93±0.73 μg/mL。經由實驗結果可以得知，白茅根乙酸乙酯層萃取物之化學成分具有抗氧化、抗痛風及抗高血壓的活性。根據上述結果，其具有開發為保健食品的潛力。

關鍵字

白茅根；黃嘌呤氧化酶抑制活性； ACE 抑制活性；抗氧化活性

並列摘要

Imperata cylindrica is a perennial herb from the Gramineae family.Its root was used for treating bleeding and nosebleed caused by the blood heat. Recently, biological activities such as anticancer, anti-gout, and lowering the blood sugar had been reported. In this study, oven-dried roots of I. cylindrica were extracted with methanol (MeOH). The MeOH crude extract was suspended in water, and then partitioned sequentially using ethyl acetate (EA) and n-butanol (n-BuOH). In the preliminary antioxidant assays, the EA layer of I. cylindrica roots exhibited antioxidant activity. The EA layer was separated into thirty-six fractions by silica gel chromatography. Furthermore, all the fractions were purified by repeated column chromatography, high performance liquid chromatography (HPLC) and recrystallization to yield twenty-nine compounds including four triterpenoid, four steroids, seven anthraquinones, six aromatics, two flavonoids, one coumarin, one chromone, two phthalides, one xanthone and one organic acid. Their structures were elucidated by spectroscopic analysis including EI-MS and 1H- and 13C-NMR techniques. In the results of antioxidant test, protocatechuic, and catenarin exhibit the significant DPPH free radical scavenging activity, with the IC50 values 9.34± 2.14, 9.90±1.57, 24.05±2.41 μg/mL, respectively. In the results of the xanthine oxidase inhibitory assay, 4 hydroxybenzaldehyde exhibit the better activity than others. Its IC50 is 8.63±0.10 μg/mL. In the result of angiotensin-converting enzyme inhibitory assay, protocatechuic, syringic acid, and methyl hydrogen fumarate exhibit the good activity. Their IC50 are 13.42, 0.25, 12.26±0.47, and 10.93±0.73 μg/mL, respectively. From the biological activity results of EA layer extract of I. cylindrica, its chemical composition display antioxidant, anti-gout, and antihypertension activities. According to the results, it has the potential to develop health foods.