檸檬果皮萃出物之抗氧化活性探討

本試驗之目的，在於探討不同溶劑萃取檸檬果皮之萃取物所含抗氧化活性及其成分（總酚與總類黃酮）之含量。結果顯示，檸檬皮之最適萃取條件為：15倍溶劑量、萃取溫度40℃及萃取時間60分鐘。溶劑萃取率之排序為甲醇＞水＞乙醇。將不同組別之萃取物，包括檸檬皮甲醇萃取物（ME）、檸檬皮乙醇萃取物（EE）、檸檬皮水萃取物（WE），以及酸化檸檬皮甲醇萃取物（AcME）進行抗氧化活性試驗之分析。在總酚含量及總類黃酮含量的結果顯示，皆以ME中的含量為最高，分別為70.52 ± 0.77 GAE mg/g dm以及65.51 ± 0.08 QE mg/g dm。此外，在2,000 mg/L的濃度下，AcME有較高的抗氧化活性，其還原力、Trolox當量抗氧化能力以及鐵離子還原力皆為最高，分別為OD_(700nm) = 2.64、58.96%以及OD_(593nm) = 1.114。在DPPH自由基清除能力方面，500ppm之AcME清除能力與BHA接近，但在亞鐵離子螯合能力方面低於EE。以HPLC分析各組萃取物之機能性成分，可以發現在酚類及類黃酮化合物部分是以橘皮苷（hesperetin）含量最多，其次為柚皮苷（naringin）、香豆酸（p-coumaric acid）及阿魏酸（ferulic acid）；在多甲氧基黃酮化合物方面則是以川陳皮素（nobiletin）含量最多，其次為甜橙黃酮（sinensetin）及橘黃酮（tangeretin）。由上述可知，檸檬果皮中含有極豐富的抗氧化成分。然而，若先將果皮以加熱酸化處理後再以甲醇萃取，其萃取物之抗氧化活性為最高。因此，AcME之萃取物應具有作為天然抗氧化物之潛力。

關鍵字

檸檬皮；酸化萃取；抗氧化活性；總酚；總類黃酮

並列摘要

The purpose of this study was to investigate the antioxidative activity and antioxidative components (including contents of phenolics and flavonoids) of lemon peels (Citrus limon) extracted with different solvents. The results showed that the optimal extraction condition of lemon peels was: solvent ratio of 15/1 (v/w), extraction temperature of 40˚C and extraction time of 60min. The order of extraction yield was methanol > water > ethanol. The lemon peel extracts, including methanol extract (ME), ethanol extract (EE), water extract (WE), and the acidified methanol extract (AcME), were used for analysis of antioxidative activity. The ME had the hightest total phenolic content and the total flavonoid content, which were 70.52 ± 0.77GAE mg/g dm and 65.51 ± 0.08QE mg/g dm, respectively. On the other hand, when the sample concentration was at 2,000 mg/L, the AcME showed the highest antioxidative activity. The reducing power, trolox equivalent antioxidant capacity, and ferric reducing antioxidant power of AcME was OD_(700nm) = 2.64, 58.96%, and OD_(593nm) = 1.114, respectively. The DPPH radical scavenging activityof AcME was similar to BHA at 500ppm, but the ferrous ion chelating capacity was lower than that of EE. The major phenolic compounds of lemon peels extract were hesperetin, naringin, p-coumaric acid, and ferulic acid. Moreover, the major polymethoxylflavones of lemon peel extracts were nobiletin, sinensetin, and tangeretin. The lemon peels were rich in antioxidative components. Nevertheless, when lemon peels treated with heating and acidification followed by methanol extraction, the highest antioxidative activity of extract was found. Therefore, AcME may be used as a natural antioxidant.

並列關鍵字

Lemon (Citrus limon) peel ； Acidifiedextraction ； Total phenolics ； Total flavonoids

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檸檬果皮萃出物之抗氧化活性探討

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