Publications by authors named "HAAJ. Korthout"

Tyrosinase (TYR) plays a key role in the enzymatic reaction that is responsible for a range of unwanted discoloration effects, such as food browning and skin hyperpigmentation. TYR inhibitors could, therefore, be candidates for skin care products that aim to repair pigmentation problems. In this study, we used a metabolomics approach combined with the isobologram analysis to identify anti-TYR compounds within natural resources, and evaluate their possible synergism with each other.

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Background: Measuring polar auxin transport (PAT) in plants and drawing conclusions from the observed transport data is only meaningful if these data are being analysed with a mathematical model which describes PAT. In this report we studied the polar auxin transport in Panax ginseng stems of different age and grown on different substrates.

Methods: We measured polar IAA transport in stems using a radio labelled IAA and analysed the transport data with a mathematical model we developed for Arabidopsis.

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Natural deep eutectic solvents (NADES) made mainly with abundant primary metabolites are being increasingly applied in green chemistry. The advantages of NADES as green solvents have led to their use in novel green products for the food, cosmetics and pharma markets. However, one of the main difficulties encountered in the development of novel products and their quality control arises from their low vapour pressure and high viscosity.

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Nuclear magnetic resonance (NMR) spectroscopy and multivariate data analyses methods are applied to the metabolic profiling of different red wines from Portugal. The water, methanol-water (1:1), and methanol fractions from solid phase extraction (SPE) with C18 resin were subjected to in vitro TNFα activity assay. Principal component analysis allowed the clear separation among the different SPE fractions according to the activity.

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The identification of active ingredients in crude plant extracts offers great advantages. In this study, nuclear magnetic resonance and chemometrics were used for the screening of in vitro anti-TNFα activity in different berry types. Solid phase extraction was applied and the resulting water, methanol-water (1:1), and methanol fractions were tested for the activity.

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Background: Causes and consequences of the complex changes in lipids occurring in the metabolic syndrome are only partly understood. Several interconnected processes are deteriorating, which implies that multi-target approaches might be more successful than strategies based on a limited number of surrogate markers. Preparations from Chinese Medicine (CM) systems have been handed down with documented clinical features similar as metabolic syndrome, which might help developing new intervention for metabolic syndrome.

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There is a great interest in the pharmacological properties of cannabinoid like compounds that are not linked to the adverse effects of Delta(9)-tetrahydrocannabinol (THC), e.g. psychoactive properties.

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The introduction of the concept of systems biology, enabling the study of living systems from a holistic perspective based on the profiling of a multitude of biochemical components, opens up a unique and novel opportunity to reinvestigate natural products. In the study of their bioactivity, the necessary reductionistic approach on single active components has been successful in the discovery of new medicines, but at the same time the synergetic effects of components were lost. Systems biology, and especially metabolomics, is the ultimate phenotyping.

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The 14-3-3 proteins are a family of ubiquitous regulatory molecules which have been found in virtually every eukaryotic organism and tissue. Discovered 34 years ago, 14-3-3 proteins have first been studied in mammalian nervous tissues, but in the past decade their indispensable role in various plant regulatory and metabolic pathways has been increasingly established. We now know that 14-3-3 members regulate fundamental processes of nitrogen assimilation and carbon assimilation, play an auxiliary role in regulation of starch synthesis, ATP production, peroxide detoxification, and participate in modulation of several other important biochemical pathways.

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Over the past few years the presence of p53-like proteins in plants was frequently reported, by using the monoclonal antibody Pab240. By means of protein purification and screening a cDNA library, a Pab240 cross-reacting protein and a cDNA clone were isolated from barley. Peptide- and DNA-sequence analysis identified one and the same protein: 2-oxoglutarate dehydrogenase.

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Fusicoccin (FC), a fungal phytotoxin, evokes a number of physiological responses after binding to the FC-binding protein (FCBP). For characterization of this plasma membrane protein and elucidation of the signal transduction pathway, we purified active FCBP from oat (Avena sativa L. cv Valiant) root plasma membranes using avidin-biotin affinity chromatography.

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