关键词: 甘薯 , 茎尖 , 醇溶提取物 , DPPH&bull, 清除率 , 反应速率 , 反应时间 , 行为特征

Abstract: 【Objective】Sweetpotato[Ipomoea batatas(L.)Lam.] vine is composed of 3 parts, namely leaf, petiole and stem. It has received more and more attentions from the researchers, consumers, and is popular in vegetable market because sweetpotato vine is an excellent source of antioxidant and is superior in its physiological health care functions to other commercial vegetables. The indexes reflecting the reaction of 1,1-diphenyl-2-picrylhydrazyl (DPPH•) scavenging of ethanol extracts from sprouting shoot tips of 65 sweetpotato clones (including 16 varieties)were investigated to explore these sweetpotato clones behavioral differences in the DPPH• scavenging reaction process.【Method】The DPPH• scavenging rates at 19 moments between 0 and 210min of the reaction duration among the ethanol extract concentration of 0.1, 0.2, 0.4, 0.8, 1.6, 2.0 mg•mL-1 from sprouting shoot tips of 65 sweetpotato clones were determined, and the reaction rate and its change, EC50 and the corresponding times spent for scavenging rate reaching 50%, 80% in all concentrations were calculated, and 65 clones were classified by cluster analysis according to these indexes.【Result】①Although behaviors of ethanol extract in their DPPH• scavenging process performed continuity among 65 clones, these clones could still be classified into five types, and types Ⅱ, Ⅲ accounted for the majority. ② The reaction rates in 0—1 min and 1—3 min, scavenging rates at 210 min under all concentrations of type Ⅰ including one clone significantly less than those of other types. And its scavenging rate could not achieve 50% even the concentration of ethanol extract increased to 2.0 mg•mL-1. ③The average antioxidant capacity of type Ⅱ with 44 clones was significantly better than that of type Ⅰ and inferior to those of other types. Only the concentration of ethanol extract reached to 0.8 mg•mL-1, scavenging rates of 24 clones in typeⅡ could attain to 50%, but that would spend 83.89 min, and none could achieve 80%. When the concentration increased to 2.0 mg•mL-1, 37 clones in typeⅡ could achieve 80% after 59.23 min. ④The scavenging rate variation curves of type Ⅲ consisting of 17 clones, scavenging rates at 210 min, EC50, reaction rates, the proportion of the number of clones which scavenging rates could reach 50% and 80% and corresponding times spent, were all between type Ⅱ and Ⅳ and deviated to the latter. ⑤Type Ⅳ contained one clone and type Ⅴ included 2 clones. EC50 of both types were lower than those of the former three types, and their scavenging rates could achieve 50% even at 0.4 mg•mL-1 and 80% at 0.8 mg•mL-1 and corresponding times spent were significantly shorter than those of the former three types. There were differences in the varying of reaction rates between type Ⅳ and Ⅴ.【Conclusion】The behavioral characteristics such as reaction rate, reaction time, scavenging rate variation corresponding to reaction process and extract concentration, and EC50 of ethanol extract from sweetpotato sprouting shoot tips duration their DPPH• scavenging reaction should be synthetically taken into account in the assaying antioxidant activity of sweetpotato shoot tips by DPPH• scavenging method.

Key words: sweetpotato , sprouting shoot tip , ethanol extract , DPPH&bull, scavenging rate , reaction rate , reaction time , behavioral characteristic