| Sweetpotato vine tips are not only rich in carbohydrates, dietary fiber, protein and so on, but also rich in carotenoids, vitamins, minerals, anthocyanins, flavonoids and other natural antioxidants,so they can against aging, prevention cancer, maintain cardiovascular fitness and other physiological health functions. Now selling fresh vine tips as food and deep processing of vine tips become the focus in the sweetpotato industy. The breeding of sweetpotato variety for vine tips-vegetable-use is one of the important direction. The forming of plant leaf color is related to itself pigments contents and changes. It is important significance for variety breeding and using of sweetpotato vine tips how to determining natural antioxidant content and antioxidant capacity of different colors sweetpotato vine tips. In present paper, basis on the measuring color values and ABTS ? scavenging capacities of lipid-soluble extraction and β- carotene contents in vine tips of 44 sweetpotato varieties, the relationships among the color values, β- carotene content and ABTS ? scavenging capacities were analyzed, in order to provide the appropriate basis for the variety breeding and deep processing of sweetpotato vine tips..The main results in this paper are as follows:1. 44 sweetpotato varieties had significant differences in five color values, namely L*、a*、b*、C、h°, of upper and lower surfaces of vine tips and were be divided into green, green with purple,yellow, purple color-types by clustering according to their color values. The color values L*, a*, b*,C, h° of 44 varieties vine tips upper surfaces variation range were 31.16-57.40,-10.24-0.76,3.47-38.94, 4.35-40.29, 81.26-116.84, respectively, and those of lower surfaces were 34.35-62.57,-8.30-7.62,-0.05-25.43, 8.61-26.26, 82.57-239.96, respectively. 44 varieties were divided into green,purple with green, purple, yellow color-types categories by clustering according to their color values and there had significant differences in color values among four color-types.There were significantly positive relation between the same color value belong to upper and lower surfaces except for h°.There were significant positive relations between color value L* and b* or C,while a * and b *, C or h° existed significant or notable negative relations among green-type varieties or among green with purple-type varieties.2. There were significant differences in β-carotene contents of vine tips among sweetpotatovarieties and β-carotene contents related to upper surface a* value of vine tips belong to green type.The contents of β-carotene in vine tip of 25 sweet potatoes varieties ranged from 0.2653 mg?g-1DW to 1.5415 mg?g-1DW, and there had significant difference between different varieties. Yu Su no. 8had the highest contents of β-carotene, 1.5415 mg?g-1DW, among these varieties, while those of varieties which serial number were 1, 4, 7, 19, 32, 41 and 44 over 1.0000mg?g-1DW. The order from higher to lower according to their average of β-carotene contents were yellow > purple > green with purple > green among four color-type. There had significant differences between yellow color-type and green color-type or green with purple color-type according to their average of β-carotene contents and no differences between yellow and purple, purple and green with purple, green and green with purple. There were significantly positive relation between β-carotene content in vine tips and a * of upper surfaces of vine tips among varieties belong to the green color-tye,.3. There were obviously differences among varieties according to their ABTS ? scavenging capacities of lipid- soluble extraction from vine tips, and the ABTS ? scavenging capacity was significantly positive relation to β-carotene contents, and β-carotene was the major antioxidant in lipid- soluble extraction from the green color type or green with purple color type. The ABTS ?scavenging rates at 10 min showed significant difference among 44 varieties. The ABTS? scavenging rates of varieties belong to subgroup 2 of green color-type were generally higher than those of other varieties. Yusu 162 had the highest ABTS? scavenging rates at 10 min, reached 85.78%, when extraction concentration was 16.0 mg?m L-1. The ABTS ? scavenging rates of green color-type had the highest among four color-types at 16.0 mg?m L-1, followed by yellow color-type, and there were no significant difference among among four color-types according to the average of ABTS?scavenging rates. At 0.5, 4.0, 8.0 mg?m L-1, The ABTS? scavenging rates of purple color-type is the highest, followed by yellow color-type. At 2.0 mg?m L-1, The ABTS? scavenging rates of purple varieties was the highest, followed by green color-type. At 1.0mg?m L-1, The ABTS? scavenging rates of four-color-types were very closed.Among four color-types, purple color-type had minimum EC50 average values, 6.63 mg?m L-1,and green with purple color-type had maximum EC50 average value, 8.12 mg?m L-1. At 2.0, 4.0, 8.0mg?m L-1, there were obviously positive relation between β-carotene contents and ABTS? scavenging rates among varieties belong to green color-type, and so as among varieties belong to green with purple color-type at 16.0 mg?m L-1. There were obviously negative relation between EC50 values and β- carotene content among the 25 varieties, which showed β- carotene were major lipid-soluble antioxidant in the green and green with purple varieties. the reaction rate of 0-1min ABTS scavenging reaction rates is significant difference, Under 2.0, 4.0, 8.0, 16.0 mg?m L-1, the 0-1min ABTS? scavenging reaction rates of the yellow color-type is the fastest than those of othercolor-types, and at 0.5 mg?m L-1, the fastest 0-1min ABTS? scavenging reaction rates is those of purple color-type.Among varieties belong to green color-type, there were significant negative relation between the EC50 value and a * of upper surfaces.Conclusion: This study showed there were significant differences among varieties in the vine tips color and the ABTS ? scavenging capacities of lipid- soluble extraction from vine tips and related to the β- carotene contents in vine tips. During the process of vine tips vegetable-use variety breeding,the a * value measured by portable colorimeter would assist to breeder in the field selecting for high lipid-soluble antioxidant activity variety or germplasm accession from breeding lines belong to green color type. |
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