title: Potato and mushroom polyphenol oxidase activities are differently modulated by natural plant extracts.
abstract: 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.
authors.affiliation: Laboratory of Food Chemistry, Wageningen University , P.O. Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Tomas F M
authors.initials: TF
authors.lastname: Kuijpers
authors.forename: Teunie
authors.initials: T
authors.lastname: van Herk
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Vincken
authors.forename: Renske H
authors.initials: RH
authors.lastname: Janssen
authors.forename: Deborah L
authors.initials: DL
authors.lastname: Narh
authors.forename: Willem J H
authors.initials: WJ
authors.lastname: van Berkel
authors.forename: Harry
authors.initials: H
authors.lastname: Gruppen
mesh_terms: D000364:Agaricus / Q000201:enzymology*; D004156:Catechol Oxidase / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000737:chemistry*; D005656:Fungal Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D030019:Ilex paraguariensis / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry; D010936:Plant Extracts / Q000737:chemistry*; D010940:Plant Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D012503:Saponins / Q000737:chemistry; D011198:Solanum tuberosum / Q000201:enzymology*
chemical_list: D004791:Enzyme Inhibitors; D005656:Fungal Proteins; D010636:Phenols; D010936:Plant Extracts; D010940:Plant Proteins; D012503:Saponins; D004156:Catechol Oxidase
keywords: Ilex paraguariensis; LC-MS; enzymatic browning; plant extracts; tyrosinase