新鮮與老化葉菜類蔬菜抗氧化力之測定

Determination of the Total Antioxidant Capacity in Fresh and Senescent Leafy Vegetables

王念慈(Nien-Tzu Wang) ； 王自存(Tsu-Tsuen Wang) ； 曹幸之(Shing-Jy Tsao)

《臺中區農業改良場研究彙報》 104期 (2009/09) Pp. 67-82

https://doi.org/10.6956/BTDAIS.200909.0067

摘要

本研究以改良之TOSC（Total oxyradical scavenging capacity）法分析葉菜之總抗氧化能力，並以6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid（Trolox）當量（Trolox equivalent antioxidant capacity, TEAC）值表示。將十七種常見葉菜分為三大群：第一群具高抗氧化能力（TEAC值在2.0 μmole/g以上），包括莧菜、山芹菜、芫荽、角菜；第二群為具中抗氧化能力（TEAC值在1.1~2.0 μmole/g之間），包括甘藷葉、芥藍、小白菜、葉萵苣、菠菜、落葵、油菜、芹菜；第三群為抗氧化能力較低者（TEAC值在1.1 μmole/g以下），包括青梗白菜、皺葉萵苣、蕹菜、半結球萵苣、茼蒿。另以DPPH（2,2’-diphenyl-1-picrylhydrazyl）法分析葉菜甲醇萃取物之自由基清除能力（以%表示）。以TOSC法與DPPH法所得之結果有所不同。兩種抗氧化力分析結果中，同樣屬於高抗氧化能力之葉菜有山芹菜與角菜，同樣屬於低抗氧化能力之葉菜有茼蒿、蕹菜及青梗白菜。莧菜與芫荽的Trolox當量高而DPPH自由基清除能力低；半結球萵苣與皺葉萵苣的Trolox當量低而DPPH自由基清除能力高。因此可知，由於反應原理與樣品準備方式不同，蔬菜之總抗氧化力以不同分析方法測定的結果，可能會有差異。葉菜類蔬菜在採後以乙烯誘導變黃、老化，其總抗氧化力之變化以TOSC法分析，結果顯示，葉萵苣、蕹菜、芥藍與紅鳳菜之總抗氧化能力有增高的趨勢，青梗白菜、莧菜、菠菜及甘藷葉於採後黃化或失去價值時的總抗氧化能力則較新鮮狀態為低。葉菜依採後總抗氧化能力之變化趨勢可分為採後下降型與採後上升型兩類。

關鍵字

自由基清除能力 ； 總抗氧化力 ； 蔬菜 ； 老化 ； 乙烯處理

並列摘要

The antioxidant capacity of 18 common leafy vegetables were assayed by modified TOSC (Total oxyradical scavenging capacity) method and expressed as the Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylicacid) equivalent antioxidant capacity (TEAC). Based on the TEAC values, tested 17 leafy vegetables could be grouped into three. The first group, with TEAC values higher than 2.0 μmole‧g^(-1) , includes amaranth, Japanese hornwort, Chinese parsley and white mugwort. The second and the largest group, with TEAC values between 1.1-2.0 μmole‧g^(-1), includes sweet potato tips, Chinese kale, pak-choi, leaf lettuce, spinach, malaber spinach, edible rape and smallage. The third group, with TEAC values less than 1.1 μmole‧g^(-1), includes chingan-cai, curled lettuce, water spinach, loose head lettuce and garland chrysanthemum.The antioxidant capacity of the same 17 leafy vegetables were also measured by the DPPH (2,2'-diphenyl-1-picrylhydrazyl) method, which measures the radical scavenging activity in methanol extracts of tissue samples. There were some differences between the results of the TOSC method and the DPPH method. Japanese hornwort and white mugwort were ranked high in antioxidant capacity by both methods. However, amaranth and Chinese parsley were ranked high in antioxidant capacity by the TOSC method but not by the DPPH method. Garland chrysanthemum, water spinach and chingan-cai were ranked low by both methods. Loose head lettuce and curled lettuce were ranked low by the TOSC method and high by the DPPH method. These are arttributed to the differences in the nature of free radical scavenging reaction as well as the ways of sample preparation, and the vegetables may thus fall into different categories of antioxidant power in two tests.The antioxidant capacities of both fresh and senescent leaves of eight leafy vegetables were determined by the TOSC method. In leaf lettuce, water spinach, Chinese kale and gynura, their antioxidant capacities increased as they turned yellow or deteriorated. In leaves of chingan-cai, amaranth, spinach and sweet potato tips, their antioxidant capacities decreased upon senescent and yellowing. Accordingly, the patterns of change in antioxidant capacity of leafy vegetables during leaf senescence could be divided into two groups: the ascending antioxidant capacity type showed an increase in antioxidant capacity during leaf senescence, and the descending type showed an decrease in leaf antioxidant capacity.

並列關鍵字

radical scavenging activity ； total antioxidant capacity ； vegetables ； senescent ； ethylene treatment