Kuijpers Tomas F M, van Herk Teunie, Vincken Jean-Paul, Janssen Renske H, Narh Deborah L, van Berkel Willem J H, Gruppen Harry
Laboratory of Food Chemistry, Wageningen University , P.O. Box 17, 6700 AA Wageningen, The Netherlands.
J Agric Food Chem. 2014 Jan 8;62(1):214-21. doi: 10.1021/jf4043375. Epub 2013 Dec 27.
Enzymatic browning is a major quality issue in fruit and vegetable processing and can be counteracted by different natural inhibitors. Often, model systems containing a single polyphenol oxidase (PPO) are used to screen for new inhibitors. To investigate the impact of the source of PPO on the outcome of such screening, this study compared the effect of 60 plant extracts on the activity of PPO from mushroom ( Agaricus bisporus , AbPPO) and PPO from potato ( Solanum tuberosum , StPPO). Some plant extracts had different effects on the two PPOs: an extract that inhibited one PPO could be an activator for the other. As an example of this, the mate ( Ilex paraguariensis ) extract was investigated in more detail. In the presence of mate extract, oxygen consumption by AbPPO was found to be reduced >5-fold compared to a control reaction, whereas that of StPPO was increased >9-fold. RP-UHPLC-MS analysis showed that the mate extract contained a mixture of phenolic compounds and saponins. Upon incubation of mate extract with StPPO, phenolic compounds disappeared completely and saponins remained. Flash chromatography was used to separate saponins and phenolic compounds. It was found that the phenolic fraction was mainly responsible for inhibition of AbPPO and activation of StPPO. Activation of StPPO was probably caused by activation of latent StPPO by chlorogenic acid quinones.
酶促褐变是果蔬加工中的一个主要质量问题，可通过不同的天然抑制剂来抑制。通常，含有单一多酚氧化酶（PPO）的模型体系用于筛选新的抑制剂。为了研究PPO来源对这种筛选结果的影响，本研究比较了60种植物提取物对蘑菇（双孢蘑菇，AbPPO）PPO和马铃薯（马铃薯，StPPO）PPO活性的影响。一些植物提取物对两种PPO有不同的作用：一种抑制一种PPO的提取物可能是另一种PPO的激活剂。作为一个例子，对马黛茶（巴拉圭冬青）提取物进行了更详细的研究。在马黛茶提取物存在的情况下，发现与对照反应相比，AbPPO的耗氧量降低了5倍以上，而StPPO的耗氧量增加了9倍以上。RP-UHPLC-MS分析表明，马黛茶提取物含有酚类化合物和皂苷的混合物。将马黛茶提取物与StPPO孵育后，酚类化合物完全消失，皂苷残留。采用快速柱色谱法分离皂苷和酚类化合物。发现酚类部分主要负责抑制AbPPO和激活StPPO。StPPO的激活可能是由绿原酸醌激活潜在的StPPO引起的。
