不同甘薯品种苗期茎尖醇溶提取物清除DPPH·的行为特征差异

Behavioral Differences of Ethanol Extracts from Sprouting Shoot Tips of Different Sweetpotato Varieties in the Process of DPPH. Scavenging Reaction

【目的】通过对65个甘薯品种苗期茎尖醇溶提取物清除1,1-二苯基-2-三硝基苯肼(DPPH.)反应过程中相关指标的研究,探索其清除DPPH.的行为特征差异。【方法】测定65个品种苗期茎尖醇溶提取物在0.1、0.2、0.4、0.8、1.6、2.0 mg.mL-16个浓度下清除DPPH.反应的0—210 min中19个时间点的DPPH.清除率,计算反应速率及其变化、各品种的EC50和各浓度下清除率达到50%与80%所需时间,并根据这些指标对65个品种进行聚类分析。【结果】甘薯苗期茎尖醇溶提取物的清除DPPH.行为在65个品种间虽然表现为连续性,但聚类分析能将其分为5种行为类型,并以类型Ⅱ、Ⅲ为主。类型Ⅰ包含1个品种,0—1 min和1—3 min的反应速率、210 min的清除率均显著小于其它类型,醇溶提取物浓度达2.0 mg.mL-1时清除率仍不能达到50%。类型Ⅱ包含44个品种,平均抗氧化能力显著优于类型Ⅰ,次于其它3种类型。醇溶提取物浓度达到0.8 mg.mL-1时有24个品种能达到50%清除能力,平均需时83.89 min,但无品种能达到80%;而2.0 mg.mL-1时有37个品种能达到80%清除率,平均需时59.23 min。④类型Ⅲ包含17个品种,其清除率曲线变化趋势、210 min的清除率、EC50、反应速率以及清除率达到50%和80%的品种比例及所需时间均介于类型Ⅱ与类型Ⅳ之间,并偏向类型Ⅳ。⑤类型Ⅳ包括一个品种,类型Ⅴ包括2个品种。两者的EC50低于前3种类型,均在0.4 mg.mL-1时就能达到50%,在0.8 mg.mL-1就能达到80%,且所需时间显著低于其它类型。而两者主要区别体现在反应速率的变化方面。【结论】在利用DPPH.清除法评定甘薯苗期茎尖醇溶提取物抗氧化能力过程中需要综合考虑清除率随反应时间、醇溶提取物浓度的变化趋势、阶段反应速率、反应消耗时间、EC50多项抗氧化反应行为特征指标。

[ Objective ] Sweetpotato[lpomoea 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.mLl 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, HI 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＇mLl. ~）The average antioxidant capacity of type 11 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＇mL1, scavenging rates of 24 clones in type II could attain to 50%, but that would spend 83.89 min, and none could achieve 80%. When the concentration increased to 2.0 mg＇mL1, 37 clones in type II could achieve 80% after 59.23 min. QThe scavenging rate variation curves of type III consisting of 17 clones, scavenging rates at 210 min, ECso, 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. （~）Type IV contained one clone and type V included 2 clones. ECs0 of both types were lower than those of the former three types, and their scavenging rates could achieve 50% even at 0.4 mg-mL1 and 80% at 0.8 mg.mL1 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.