Karin Schwarz

Bio: Karin Schwarz is an academic researcher from University of Kiel. The author has contributed to research in topics: Lipid oxidation & Chemistry. The author has an hindex of 40, co-authored 127 publications receiving 4715 citations. Previous affiliations of Karin Schwarz include University of Münster.

Genome-wide association analysis identifies variation in vitamin D receptor and other host factors influencing the gut microbiota

Abstract: Human gut microbiota is an important determinant for health and disease, and recent studies emphasize the numerous factors shaping its diversity. Here we performed a genome-wide association study (GWAS) of the gut microbiota using two cohorts from northern Germany totaling 1,812 individuals. Comprehensively controlling for diet and non-genetic parameters, we identify genome-wide significant associations for overall microbial variation and individual taxa at multiple genetic loci, including the VDR gene (encoding vitamin D receptor). We observe significant shifts in the microbiota of Vdr-/- mice relative to control mice and correlations between the microbiota and serum measurements of selected bile and fatty acids in humans, including known ligands and downstream metabolites of VDR. Genome-wide significant (P < 5 × 10-8) associations at multiple additional loci identify other important points of host-microbe intersection, notably several disease susceptibility genes and sterol metabolism pathway components. Non-genetic and genetic factors each account for approximately 10% of the variation in gut microbiota, whereby individual effects are relatively small.

Investigation of plant extracts for the protection of processed foods against lipid oxidation. Comparison of antioxidant assays based on radical scavenging, lipid oxidation and analysis of the principal antioxidant compounds

Abstract: Antioxidant activities of plant extracts from spices, coffee, tea, grape skin, and tomato peel slurry were evaluated using a number of analytical methods including the quantification of principal compounds. Similar rankings in the activities of these extracts were obtained by evaluating their efficiencies as scavengers of stable free radicals: Fremy's salt, galvinoxyl or α,α-diphenyl-β-picrylhydrazyl (DPPH). Similar results were obtained with the lipid oxidation assays based on thermal acceleration (formation of conjugated dienes in methyl linoleate at 40 °C or the Rancimat test at 100 °C with lard). Rankings of the extract activity obtained by scavenging of hydroxyl radicals generated in the Fenton reaction were similar to those obtained by an oxygen consumption assay with linoleic acid as substrate and metmyoglobin as catalyst. However, the results of the latter two assays differed from those of the other assays. In the overall ranking, coffee and rosemary extracts were amongst the most potent extracts whereas the tomato peel slurry showed no activity.

Identification of flavonoids and hydroxycinnamic acids in pak choi varieties (Brassica campestris L. ssp. chinensis var. communis) by HPLC-ESI-MSn and NMR and their quantification by HPLC-DAD.

Abstract: Twenty-eight polyphenols (11 flavonoid derivatives and 17 hydroxycinnamic acid derivatives) were detected in different cultivars of the Chinese cabbage pak choi ( Brassica campestris L. ssp. chinensis var. communis) by HPLC–DAD–ESI-MS n . Kaempferol was found to be the major flavonoid in pak choi, glycosylated and acylated with different compounds. Smaller amounts of isorhamnetin were also detected. A structural determination was carried out by 1H and 13C NMR spectroscopy for the main compound, kaempferol-3- O-hydroxyferuloylsophoroside-7- O-glucoside, for the first time. Hydroxycinnamic acid derivatives were identified as different esters of quinic acid, glycosides, and malic acid. The latter ones are described for the first time in cabbages. The content of polyphenols was determined in 11 cultivars of pak choi, with higher concentrations present in the leaf blade than in the leaf stem. Hydroxycinnamic acid esters, particularly malic acid derivatives, are present in both the leaf blade and leaf stem, whe...

Reactive Oxygen Species, Oxidative Damage, and Antioxidative Defense Mechanism in Plants under Stressful Conditions

Abstract: Reactive oxygen species (ROS) are produced as a normal product of plant cellular metabolism. Various environmental stresses lead to excessive production of ROS causing progressive oxidative damage and ultimately cell death. Despite their destructive activity, they are well-described second messengers in a variety of cellular processes, including conferment of tolerance to various environmental stresses. Whether ROS would serve as signaling molecules or could cause oxidative damage to the tissues depends on the delicate equilibrium between ROS production, and their scavenging. Efficient scavenging of ROS produced during various environmental stresses requires the action of several nonenzymatic as well as enzymatic antioxidants present in the tissues. In this paper, we describe the generation, sites of production and role of ROS as messenger molecules as well as inducers of oxidative damage. Further, the antioxidative defense mechanisms operating in the cells for scavenging of ROS overproduced under various stressful conditions of the environment have been discussed in detail.

Antioxidant activity and phenolic compounds in selected herbs

Abstract: The antioxidant capacities (oxygen radical absorbance capacity, ORAC) and total phenolic contents in extracts of 27 culinary herbs and 12 medicinal herbs were determined. The ORAC values and total phenolic contents for the medicinal herbs ranged from 1.88 to 22.30 μmol of Trolox equivalents (TE)/g of fresh weight and 0.23 to 2.85 mg of gallic acid equivalents (GAE)/g of fresh weight, respectively. Origanum × majoricum, O. vulgare ssp. hirtum, and Poliomintha longiflora have higher ORAC and phenolic contents as compared to other culinary herbs. The ORAC values and total phenolic content for the culinary herbs ranged from 2.35 to 92.18 μmol of TE/g of fresh weight and 0.26 to 17.51 mg of GAE/g of fresh weight, respectively. These also were much higher than values found in the medicinal herbs. The medicinal herbs with the highest ORAC values were Catharanthus roseus, Thymus vulgaris, Hypericum perforatum, and Artemisia annua. A linear relationship existed between ORAC values and total phenolic contents of th...

The use of the stable free radical diphenylpicrylhydrazyl (dpph) for estimating antioxidant activity

Abstract: Molyneux, P. The use of the stable free radical diphenylpicrylhydrazyl (DPPH) for estimating antioxidant activity