新鮮與老化葉菜類蔬菜之總抗氧化力之測定與變異

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

王念慈(Nien-Tzu Wang)

指導教授 ： 王自存

共同指導教授 ： 曹幸之(Shing-Jy Tsao)

國立臺灣大學/生物資源暨農學院/園藝學研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.01392

摘要

本研究改良MacLean等人[Postharvest Biol. Technol. 29(2003):183] 提出之總抗氧化能力分析法 ( TOSC assay )，以改進其結果之精確度。原方法以針筒將自由基產生者 2,2’-azobis-amidinopropane (ABAP) 注入試管的方式，被改為以微量吸管加入試管後迅速封說C利用修改步驟後之TOSC法測定常見蔬菜之抗氧化能力，其中菠菜與青花菜具有較高的抗氧化能力，餘由高到低依序為油菜、葉萵苣、青梗白菜、半結球萵苣、蕹菜、花椰菜。
以TOSC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，可將十七種常見葉菜分為三大群：第一群具高抗氧化能力的 (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的 (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。第三群為具低抗氧化能力的 (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)，結果顯示以TOSC法與DPPH法之結果有所不同。二種抗氧化力分析結果中，同時屬於高抗氧化能力之葉菜有山芹菜與角菜，同時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，蔬菜用不同之總抗氧化力分析方法測定的結果，可能會有差異。
葉菜類蔬菜在變黃老化後，其總抗氧化力之變化，以TOSC分析結果顯示，葉萵苣、蕹菜、芥藍與紅鳳菜在採後之總抗氧化能力有增高的趨勢；青梗白菜、莧菜、菠菜以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。根據此結果可將葉菜依採後總抗氧化能力之變化趨勢大別為採後下降型與採後上升型兩類。

關鍵字

老化 ； 自由基 ； 抗氧化 ； 蔬菜

並列摘要

The modified total oxyradical scavenging capacity (TOSC) assay for antioxidants in plant tissues reported by MacLean et al. [Postharvest Biol. Technol. 29(2003):183] was further modified to improve its accuracy. The original method of injecting the radical generator 2,2’-azobis-amidinopropane (ABAP) into the sealed reaction vial through a syringe was replaced by pipetting equivalent amount of ABAP into the test vial followed by sealing the vial with a serum cap immediately. This re-modified TOSC method was used to evaluate the total antioxidant capacity of several common vegetables. Spinach and broccoli were found to have higher antioxidant capacity followed by rape, leaf lettuce, chingan cai, loose head lettuce, water spinach and cauliflower in descending order.
Mature leaves of 17 common leafy vegetables were assayed by this re-modified TOSC method and their results were expressed as the Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid) equivalent antioxidant capacity (TEAC). The TEAC of 17 common leafy vegetables could be divided into three groups: the first group, with their TEAC values higher than 2.0 μmole/g , included amaranth, hornwort, Chinese parsley and white mugwort; the second group, with their TEAC values between 1.1 - 2.0 μmole/g, included sweet potato tips, Chinese kale, pak-choi, leaf lettuce, spinach, malaber spinach, rape and smallage; the third group, with their TEAC values less than 1.1 μmole/g, included chingan cai, curled lettuce, water spinach, loose head lettuce and garland chrysanthemum.
The antioxidant capacity of these 17 common 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 sample. There were substantial differences between the results of the TOSC method and the DPPH method. Hornwort and white mugwort ranked as high in antioxidant capacity by both methods; but amaranth and Chinese parsley ranked high by the TOSC method but low by the DPPH method. On the other hand, garland chrysanthemum, water spinach and chingan cai ranked low by both methods, but loose head lettuce and curled lettuce ranked low by the TOSC method and high by the DPPH method. These results indicated that owing to differences in the nature of free radical scavenging reaction as well as to ways of sample preparation, results of antioxidant capacity measurement may fall into different categories.
The antioxidant capacities in the fresh and senescent leaves of eight leafy vegetables were determined by the TOSC method. In leaves of leaf lettuce, water spinach, Chinese kale and gynura, their antioxidant capacities increased when it turned yellow or deteriorated. In leaves of chingan cai, amaranth, spinach and sweet potato tips, their antioxidant capacities decreased when it turned yellow. According to these results, the patterns of change in antioxidant capacity of leafy vegetables during leaf senescence could be divided into two groups: the ascending type showed an increase trend in their antioxidant capacity during senescence, the descending type showed an decrease trend in their antioxidant capacity.

並列關鍵字

senescence ； free radical ； TOSC ； antioxidant ； DPPH ； vegetables

參考文獻

劉慧瑛、黃淵輝. 1991. 台灣水果維他命C含量之測定. 中華農業研究 40:280-290.

Anderson, D. and B. J. Phillips. 1999. Comparative In Vitro and In Vivo effects of antioxidants. Food Chem. Toxic. 37:1015-1025.

Arnao, M. B., A. Cano, J. Hernández-Ruiz, F. García-Cánovas, and M. Acosta. 1996. Inhibition by L-ascorbic acid and other antioxidants of the 2,2’-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) oxidation catalyzed by peroxidase: a new approach for determining total antioxidant status of foods. Analytical Biochem. 236:255-261.

Bendich, A. 1990. Antioxidant nutrients and immune function, p.1-12. In: Antioxidant nutrients and immune functions. Vol. 262. Plenum Press, New York.

Benzie I. F. F. and J. J. Strain. 1996. The ferric reducing ability of plasma (FRAP) as a measure of ‘Antioxidant Power’ : the FRAP assay. Anal. Biochem. 239:70-76.