Optimization Of Alcohol Extraction Conditions Of Polyphenol From Different Flesh Colors Storage Roots Of Sweetpotato And Their DPPH· Scavenging Abilities

Sweetpotato (Ipomoea batatas(L.) Lam.) storage roots are rich in carbohydrates, dietary fiber, proteins, minerals and so on, but also rich in natural antioxidation, such as chlorogenic acid, anthocyanins, flavonoids, carotenoids, vitamins, alkaloids, tannins etc., so sweetpotato have antioxidant, anti-cancer, anti-inflammatory, antibacterial and other health care functions. Studing and exploring above functions of sweetpotato storage roots with different flesh color such as white, pale yellow, yellow, orange, orange red, lavender, purple, dark purple are important for sweetpotao industrialization. In present paper, in order to breeding and industrialization of sweetpotato function-varieties, after determinating chromatic value of storage roots dry powder of 78 sweetpotato varieties with five fleshed-color, alcohol extraction conditions of polyphenols in 11 different flesh colors storage roots were optimized by response surface methodology, and then DPPH-scavenging activity and polyphenol content of alcohol extraction solutions were determined for all varieties, finally, the relationships among DPPH-scavenging activity, polyphenol contents and chromatic values were studied.The main results obtained in this study are as follows:1. Chromatic values of dry powder of sweetpotato storage root show differences and regularity. Their average values of chromatic indexes are order for L*> h°>C> b* (a*) among five fleshed-color storage roots. The averages of L* and h° of 22 purple-fleshed sweetpotato varieties are the lowest among five fleshed-color storage roots, and L* and h° of non-purple-fleshed sweetpotato overlap each other. The a* in purple-fleshed sweetpotato is the highest among five fleshed-color, and the a* decreased according to the order of orange red, orange, yellow followed pale yellow. The b* in orange red-fleshed sweetpotato is the highest among five fleshed-color, and the b* decreased according to the order of orange, yellow, pale yellow overlapped by those of purple-fleshed. The average C in orange red is the highest among five fleshed-color, and the C decreased according to the order of orange, yellow, pale yellow, and overlapped by those of purple-flesed. Colorimeter not only quantitative determines the color of storage roots, but more correctely qualitative judges the color of sorage roots than human naked eye.2. The ethanol concentration, extraction time, solid-liquid ratio concerning in single-factor experiment about alcohol extraction from sweetpotato dry power obtained optimum conditions, that is 60%,9 h,10 mg·mL-1, respectively. Response surface methodology about alcohol extraction condition of polyphenols in storage roots of 11 sweetpotato varieties showed there were not significant difference among those polyphenol contents determined under the optimal conditions, under condition of 60%,9 h,10 mg·mL-1 and the polyphenol contents predicted under optimal conditions. Subsequently, the general alcohol extraction condition of polyphenol in sweetpotao storage roots are 60% ethanol concentration,9 h extraction time,10 mg·mL-1 solid-liquid ratio.Under this condition, the range of polyphenol content among 78 sweetpotato varieties was 214.06-1875.96 mg·100g-1DW, and there have significant differences among these varieties. The polyphenol contents of Yanzishu 761, contenting 1875.96 mg-100g-1 DW, is extremely significant higher than those of other purple-fleshed varieties. The polyphenol content of Xushu 22, contenting 214.06 mg·100g-1DW, is extremely significant lower than those of other-fleshed varieties. The averages of polyphenols contents among five fleshed-color are orange red> purple> orange> yellow> pale yellow, and there have no significant difference between the former two, no significant difference among the latter three.3. DPPH-scavenging amount and EC50 values show difference existing among 78 sweetpotato varieties with five fleshed-color. DPPH-scavenging amounts of 22 purple-fleshed sweetpotato varieties were generally higher, up to 113.24μg in Yanzishu 761. Orange red-fleshed sweetpotato shows also higher DPPH-scavenging amounts which some were higher than those of purple-fleshed. Five pale yellow-fleshed sweetpotato had lowest DPPH-scavenging amounts, low to 0.73μg in 2010235. The range of EC50 values among 78 sweetpotato varieties was 0.98-17.72 mg·-mL-1, the minimum is 0.98 mg-mL-1 of Yanzishu 761 and 2010275, the maximum was 17.72 mg-mL-1 of Xushu 22. The averages of EC50 in five fleshed-color are purple> orange red> orange> yellow> pale yellow. The results of DPPH-scavenging of sweetpotato show that function-variety breeding should conducted among sweetpotato lines with purple, and orange red-fleshed.4. There are correlationshipns amonge DPPH-scavenging amount, EC50 values, polyphenol contents and chromatic values. DPPH-scavenging amount, EC50 values and polyphenol content were significantly correlated each other. The relationship between EC50 and chromatic values performed as follows:EC50 value has significant positive correlation with a* in purple-fleshed sweetpotato, and has significant positive partial correlation in the orange red-fleshed sweetpotato; EC50 value have significant positive correlation with L*, significant negative correlation with b* and have no correlation and partial correlation with a* in the orange-fleshed sweetpotato; EC50 values and a*, b* have no significant correlation or partial correlation in yellow or pale yellow-fleshed sweetpotato. The effect of polyphenol on chromatic values of sweetpotato storage roots are opposed to the correlationships between EC50 values and chromatic values, namely in purple-fleshed sweet potato, the polyphenol content is higher, the chromatic values showing darker (L* is smaller), more red (a* is greater), more blue (b* is smaller), but in orange red fleshed and orange-fleshed sweetpotato, the polyphenol content is higher, the chromatic values more yellow. Correlatioships among DPPH-scavenging amount, EC50 values, polyphenol contents, chromatic values show there is a possible of colorimeter used in sweetpotao breeding.Conclusion:This study shows there are significant differences among chromatic values of sweetpotato storage roots due to differences in polyphenol contents, and significant different in DPPH-scavenging abilities. Function-variety breeding should conduct among sweetpotato lines with purple, orange red -fleshed. Among purple-fleshed sweetpotato lines, a* is greater, and L*, b* and h° are smaller, polyphenol content is higher, the antioxidant capacity is stronger. Among orange red-fleshed sweetpotato, a* and L* are smaller, b* is higher, polyphenol content is higher, the antioxidant capacity is stronger. L*, a* and b* can be determined handily, fastly by colorimeter.