Publications by authors named "Kristof Csepregi"

UV-B radiation can substantially impact plant growth. To study UV-B effects, broadband UV-B tubes are commonly used. Apart from UV-B, such tubes also emit UV-A wavelengths.

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Plants are continuously exposed to combinations of abiotic and biotic stressors. While much is known about responses to individual stressors, understanding of plant responses to combinations of stressors is limited. The effects of combined exposure to drought and UV radiation are particularly relevant in the context of climate change.

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Grape pomace is a valuable source of various bioactive compounds such as plant-derived polyphenols and polyunsaturated fatty acids (PUFAs). The commercial demand of grape skin and seed powders as nutraceuticals is still growing. However, no distinction is currently made between unfermented native grape seed and grape seed pomace powders regarding their antioxidant activities.

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Tobacco plants were grown in plant chambers for four weeks, then exposed to one of the following treatments for 4 days: (1) daily supplementary UV-B radiation corresponding to 6.9 kJ m d biologically effective dose (UV-B), (2) daily irrigation with 0.1 mM hydrogen peroxide, or (3) a parallel application of the two treatments (UV-B + HO).

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Photosynthesis parameters, adaxial flavonoid index, phenolic profiles and antioxidant capacities of south-facing sun exposed grapevine leaves (Vitis vinifera, Pinot Noir cultivar) were measured hourly between 7 a.m. and 7 p.

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Over the past decades, nanotechnology has received great attention and brought revolutionary solutions for a number of challenges in scientific fields. Industrial, agricultural and medical applications of engineered nanomaterials have increased intensively. The ability of titanium dioxide nanoparticles (TiO NPs) to produce reactive oxygen species (ROS), when excited by ultra-violet (UV) light, makes them useful for effectively inactivate various pathogens.

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Introduction: Phenolic compounds are a chemically diverse group of plant secondary metabolites with important roles both in plant stress defence and human nutrition.

Objective: To explore structure-function relations potentiating phenolic compounds to promote leaf acclimation to light stress by excess photosynthetically active radiation (photoinhibition) and by solar ultraviolet (UV) radiation.

Methodology: We report singlet oxygen and hydrogen peroxide antioxidant capacities and UV-absorbing properties of 27 flavonoids and 11 phenolic acids.

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A 2-year study explored metabolic and phenotypic plasticity of sun-acclimated Vitis vinifera cv. Pinot noir leaves collected from 12 locations across a 36.69-49.

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Assays assessing non-enzymatic hydrogen peroxide antioxidant capacities are often hampered by the high UV absorption of the sample itself. This is a typical problem in studies using plant extracts with high polyphenol content. Our assay is based on comparing the 405 nm absorption of the product of potassium iodine and hydrogen peroxide in the presence and absence of a putative hydrogen peroxide reactive antioxidant.

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Mature berries of Pinot Noir grapevines were sampled across a latitudinal gradient in Europe, from southern Spain to central Germany. Our aim was to study the influence of latitude-dependent environmental factors on the metabolite composition (mainly phenolic compounds) of berry skins. Solar radiation variables were positively correlated with flavonols and flavanonols and, to a lesser extent, with stilbenes and cinnamic acids.

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Thirty-seven samples of naturally occurring phenolic compounds were evaluated using three common in vitro assays for total antioxidant activity (TAC) testing: the Trolox Equivalent Antioxidant Capacity (TEAC), the Ferric Reducing Antioxidant Potential (FRAP) and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, in addition to the Folin-Ciocalteu reagent reactivity (FCR). We found that antioxidant hierarchies depended on the choice of assay and applied ANOVA analyses to explore underlying structure-TAC dependencies. In addition to statistically confirming the empirically established connection between flavonoid ring-B catechol and high TEAC or FRAP, new correlations were also found.

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