中國橄欖果實萃取物抗氧化特性及對低密度脂蛋白修飾作用之保護效應

Antioxidative Properties and Protective Effects of Extracts from Fruits of Canarium album Raeusch. on The Modification of LDL

劉子豪(Zih-Hao Liou)

指導教授 ： 陳惠英

中臺科技大學/健康科學院/食品科技研究所/碩士(2010年)

摘要

研究顯示糖尿病患的血管併發症如動脈粥狀硬化與高血糖濃度有關，高血糖濃度與血管併發症的致病機轉中扮演了重要角色，高血糖濃度會導致蛋白質糖化作用，形成早期糖化產物與最終糖化產物，可能是導致糖尿病併發症的主要原因。研究顯示糖尿病病患較一般人更易罹患動脈粥狀硬化症，而糖尿病併發動脈粥狀硬化症主要造成的原因為LDL的氧化與糖化作用。
本研究利用數種溶劑萃取中國橄欖果實，探討其抗氧化特性及對LDL修飾作用的保護效應，並分析中國橄欖果實萃取物之酚類及類黃酮含量，以瞭解中國橄欖果實於預防糖尿病併發症之發展潛力。
抗氧化試驗結果顯示，六種不同溶劑萃取物中水/酒精萃取物(WEE)具有較佳的抗氧化能力、清除自由基及抑制白蛋白氧化能力，而甲醇萃取物(ME)則具有較佳的螯合鐵離子之效果及抑制亞麻油酸自氧化能力。
酚類化合物含量分析結果顯示水酒精萃取物(WEE)含有較高含量的總多酚及類黃酮，其含量分別為190.7±6.0 mg/g及14.9±0. 2 mg/g，其次為水萃取物(WE)及酒精萃取物(EE)。高效能液相層析結果顯示中國橄欖果實萃取物含有沒食子酸。相關性分析試驗顯示中國橄欖果實萃取物的清除自由基及抑制白蛋白氧化能力與其總酚類含量呈現正相關。
進一步探討四種較具抗氧化能力之中國橄欖果實萃取物對於LDL氧化修飾之影響，其試驗結果顯示水/酒精萃取物(WEE)抑制共軛雙烯生成量、LDL蛋白質部分的氧化修飾及apoB蛋白的斷裂效果較佳，而水萃取物(WE)則對於LDL中TBARS生成量具有較佳的抑制能力。在LDL糖化試驗方面， 隨LDL糖化作用時間增長，LDL之糖化程度亦隨之增加，而中國橄欖果實萃取物則可有效抑制LDL糖化程度，其中以水/酒精萃取物(WEE)及水萃取物(WE)之抑制效果較好。
進一步將水/酒精萃取物(WEE)以正己烷、乙酸乙酯、丙酮、酒精、甲醇及水六種不同溶劑進行區分，並分析區分物之抗氧化及總酚類含量試驗，結果顯示水區分物(WF)及甲醇區分物(MF)具有較高的總酚類含量，與其抗氧化性及抑制亞麻油酸自氧化能力的趨勢相似，利用相關性分析，結果發現水/酒精萃取物(WEE)之區分物中總酚類含量與清除ABTS+自由基及抑制亞麻油酸自氧化能力呈現正相關。
綜合以上所述，中國橄欖果實萃取物具有良好的抗氧化性及對LDL修飾作用的保護效應，因此中國橄欖果實萃取物應具有預防糖尿病併發症之發展潛力。

關鍵字

動脈粥狀硬化症 ； 糖化作用 ； 抗氧化 ； 中國橄欖 ； 低密度脂蛋白

並列摘要

Large prospective clinical studies have shown a strong relationship between glycemia and diabetic microvascular complications as arteriosclerosis, retinopathy, and cataracts in diabetes. Hyperglycemia seems to have important roles in the pathogenesis of macrovascular complications. Hyperglycaemia causes increased protein glycation and the formation of early glycation products and advanced glycation end products (AGEs) which are major factors responsible for the complications of diabetes. Induction of lipoxidative and glycoxidative stress by hyperglycemia is now considered to be a key step in the modifications of lipoproteins that lead to atherosclerosis.
The objectives of this study were to investigate the antioxidative properties and the protective effects of various solvent extracts from fruit of Canarium album Raeusch. on the modification of LDL induced by Cu2+ and glucose. Correlations between phenolic, flavonoid and antioxidant activity and anti-glycation activity were also analysed to identify the components that are responsible for the antioxidant activity and anti-glycation activity of Chinese olive fruit extracts.
The results indicated that water/ethanol (1/1) extracts (WEE) of Chinese olive fruit showed well antioxidant properties, scavenging effects on free radicals and inhibitory effects on oxidation of albumin, and the methanol extracts (ME) also showed well chelating activity on metal ions and inhibitory effects on autoxidation of linoleic acid.
The highest amounts of phenolic compounds and flavonoids were found in WEE. Gallic acid was identified by HPLC analyses. The results also showed that the radicals scavenging activity and inhibition effects on oxidation of albumin of extracts correlated significantly with the content of total phenolic compounds.
Water extracts (WE) and WEE effectively increased the resistance of LDL to oxidation caused by Cu2+. The formation of conjugated dienes, thiobarbituric acid relative substances (TBARS), relative electrophoretic mobility and apoB protein fragmentationin in copper-induced LDL oxidation were significantly inhibited by WE and WEE. The glycation modification of LDL was also decreased by Chinese olive fruit extracts, especially WE and WEE showed better inhibitory effects than that of other extracts.
WEE was extracted by hexane, acetone, ethyl acetate, methanol, ethanol and water to obtain the various fractions. The results showed that water fration (WF) and methanol fraction (MF) contained higher phenolic compounds than other fractions and exhibited more inhibitory effects on autoxidation of linoleic acid and scavenging activity on radicals.
According to the results obtained, extracts of Chinese olive fruit are potent antioxidant and antiglycation agents toward copper-induced and glucose-induced LDL modification, which should have the potential to prevent the development of complications in diabetic.

並列關鍵字

Low density lipoprotein ； Chinese olive (Canarium album Raeusch.)

參考文獻

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