| 摘要: | 海巴戟天(Morinda citrifolia)，屬於茜草科（Rubiaceae），其俗名為Noni，主產於夏威夷群島、大溪地與熱帶亞洲國家，依據民間傳統療法的資料顯示，海巴戟天的樹皮、莖、根、葉、果皆可調製，相傳有糖尿病、高血壓與癌症的預防及治療等醫療保健?效C本論文首要目的是針對不同的海巴戟天之葉、莖及果實粗萃取物進行抗氧化活性分析；並藉抗氧化活性分析的結果確立最佳材料來源與萃取條件。萃取條件使用 80℃ 熱水、50 % 與 99.5% 乙醇、乙酸乙酯及超臨界二氧化碳等萃取方法，抗氧化活性分析採用 Trolox 當量的抗氧化能力、還原力、清除 DPPH 自由基能力、清除活性氧的能力（超氧陰離子、氫氧自由基及過氧化氫等）以及螯合鐵能力。結果顯示海巴戟天的葉在不同溶劑萃取下，存在各式抗氧化活性的能力，顯示海巴戟天的葉中存在極性與非極性的抗氧化成分；高螯合鐵能力成分傾向存在於葉中極性部分，還原力、清除O2-‧與 H2O2 的能力傾向存在於葉中非極性部分，清除氫氧自由基能力則多存在於葉中醇溶性部分。海巴戟天之褐莖萃取物，以超臨界二氧化碳萃取的方式所得之抗氧化活性較高，顯示褐莖中抗氧化物質多屬於非極性。不論是何種萃取條件，海巴戟天果實及青莖萃取物的抗氧化活性普遍較差。綜合來說，就材料而言，海巴戟天的葉中萃取物能偵測出較多樣的抗氧化特性與較高的活性，值得作為進一步純化抗氧化物質的材料來源；就萃取條件而言，以乙醇萃取的方法能得到較高的總抗氧化活性，其中又以清除氫氧自由基能力為主。
本論文第二個目的是評估海巴戟天粗萃取物的抗氧化活性與其化學成份的相關性，結果顯示了海巴戟天葉之乙醇萃取物含有較高的總酚類化合物及類黃酮並且與其抗氧化活性有關，但海巴戟天超臨界二氧化碳萃取物的總酚類化合物含量普遍較低。第三個目的是評估海巴戟天萃取物在保護生物細胞膜及 DNA免於氧化性傷害之能力，結果顯示海巴戟天葉之 99.5% 乙醇萃取物對LYD三品系肉豬肝臟微粒體脂質過氧化具有顯著性的抑制能力，此結果可能與其清除氫氧自由基的能力為主有關，並與多酚類物質相關。另一方面海巴戟天葉之熱水及 50% 乙醇萃取物在保護氫氧自由基誘導無細胞膜之人類淋巴球 DNA 氧化傷害上卻出現了較佳的能力，這可能是因其具有強的金屬離子螯合能力及有力的清除氫氧自由基能力。相較之下，海巴戟天葉之99.5% 酒精及乙酸乙酯萃取物在較高劑量（10-100 μg/mL）時反而呈現了促氧化之現象，推測會造成此現象的原因可能是海巴戟天葉之 99.5% 乙醇及乙酸乙酯萃取物具有較高的還原力，會將金屬離子還原而造成促氧化作用。
Morinda citrifolia（Rubiaceae）, commonly known as Noni, is a plant typically found in the Hawaiian, Tahitian and tropical Asia. The bark, stem, roots, leaves, and fruits have been used traditionally as a folk remedy for many diseases including diabetes, hypertension, and cancer. The first purpose of this study was focused on the antioxidative properties of various crude extracts from leaves, stems and fruits of Noni. With the results of antioxidative analysis, the optimal material of Noni plant and extract condition would be defined. Hot water (80℃), 50% aqueous or absolute ethanol, ethyl acetate and supercritical fluid carbon dioxide (SF-CO2) were used as solvents to extract. The antioxidative activity of crude extracts were measured by Trolox equivalent antioxidant capacity (TEAC) assay, the reducing power assay, the bleaching of 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH) free radical, the scavenging ability of reactive oxygen species (superoxide ion, hydroxyl radical and hydrogen peroxides) and the chelating activity on ferrous ions. The results suggested that antioxidative activity of Noni’s extracts might be due to both polar and non-polar compounds. Hot water and 50 % aqueous ethanol extracts from leaves and stems exhibited higher chelating activity on ferrous ions. Ethyl acetate extracts from leaves showed the highest scavenging ability of superoxide ion, and SF-CO2（1500 psi）extracts from leaves displayed significantly the scavenging ability of hydrogen peroxides. On the other hand, the absolute ethanol extracts of Noni’s leaves and green stems, and the SF-CO2 （3500 psi） extracts of brown stems had higher scavenging ability to hydroxyl free radical. However, fruits extracts were showed very poor as antioxidants. To sum up, leaves of Noni exhibited higher and variety of antioxidative activity, which is comparable to that of both stems and fruits. Noni leaf is worth further research in purification and identification of active compounds. As for extraction condition, ethanol extracts had higher total antioxidative activity, especially in scavenging of hydroxyl radical.The second purpose was to study the relationship between the antioxidative activities and chemical constituents in the crude extracts of Noni. The data showed that ethanolic extracts of Noni’s leaves had higher total polyphenolic and flavonoid contents and revealed that these compounds played a part in antioxidative activities. However, SF-CO2 extraction of Noni generally had lower total polyphenolic contents. The third study was to prove the Noni’s extracts in the protection ability of biological cell membrane and DNA which were attacted by oxidative damage. The results indicated that the absolute ethanol extracts of Noni’s leaves display significantly the inhibition ability of lipid peroxidation of microsomes from LYD pig liver. The scavenging mechanism of the absolute ethanol extracts of Noni’s leaves might have relation with hydroxyl radical. The antioxidant components might be attributed to higher content of polyphenolic compounds. On the other hand, the hot water and 50% ethanolic extracts of Noni’s leaves display the better protection ability from hydroxyl radical-induced, DNA damage in human lymphocyte without cell membrane. The antioxidant mechanism may be attributed to a strong metal-chelating ability and their effectiveness as good scavengers of hydroxyl radicals. By contrast, the absolute ethanol and ethyl acetate extracts of Noni’s leaves showed the pro-oxidative activity in the higher dosage extracts (10-100 μg/mL). The higher reducing power, which reduced the ferric ion to ferrous ion, appeared to be responsible for the pro-oxidative activity of the absolute ethanol and ethyl acetate extracts of Noni’s leaves. |
