Antioxidant,metal-binding and DNA-damaging properties of flavonolignans: A joint experimental and computational highlight based on 7-O-galloylsilybin

Besides the well-known chemoprotective effects of polyphenols, their prooxidant activities via interactions with biomacromolecules as DNA and proteins are of the utmost importance. Current research focuses not only on natural polyphenols but also on synthetically prepared analogs with promising biological activities. In the present study, the antioxidant and prooxidant properties of a semi-synthetic flavonolignan 7-O-galloylsilybin (7-GSB) are described. The presence of the galloyl moiety significantly enhances the antioxidant capacity of 7-GSB compared to that of silybin (SB). These findings were supported by electrochemistry, DPPH (2,2-diphenyl-1-picrylhydrazyl) scavenging activity, total antioxidant capacity (CL-TAC) and DFT (density functional theory) calculations. A three-step oxidation mechanism of 7-GSB is proposed at pH 7.4, in which the galloyl moiety is first oxidized at E_p,1 = +0.20 V (vs. Ag/AgCl_{3M KCl}) followed by oxidation of the 20-OH (E_p,2 = +0.55 V) and most probably 5-OH (E_p,3 = +0.95 V) group of SB moiety. The molecular orbital analysis and the calculation of O–H bond dissociation enthalpies (BDE) fully rationalize the electrooxidation processes. The metal (Cu²⁺) complexation of 7-GSB was studied, which appeared to involve both the galloyl moiety and the 5-OH group. The prooxidant effects of the metal-complexes were then studied according to their capacity to oxidatively induce DNA modification and cleavage. These results paved the way towards the conclusion that 7-O-galloyl substitution to SB concomitantly (i) enhances antioxidant (ROS scavenging) capacity and (ii) decreases prooxidant effect/DNA damage after Cu complexation. This multidisciplinary approach provides a comprehensive mechanistic picture of the antioxidant vs. metal-induced prooxidant effects of flavonolignans at the molecular level, under ex vivo conditions.     

Culturable bacterial microbiota of Plagiodera versicolora (L.) (Coleoptera: Chrysomelidae) and virulence of the isolated strains

Plagiodera versicolora (Laicharting, 1781) (Coleoptera: Chrysomelidae) is an important forest pest which damages many trees such as willow, poplar, and hazelnut. In order to find new microbes that can be utilized as a possible microbial control agent against this pest, we investigated the culturable bacterial flora of it and tested the isolated bacteria against P. versicolora larvae and adults. We were able to isolate nine bacteria from larvae and adults. The isolates were characterized using a combination of morphological, biochemical, and physiological methods. Additionally, we sequenced the partial sequence of the 16S rRNA gene to verify conventional identification results. Based on characterization studies, the isolates were identified as Staphylococcus sp. Pv1, Rahnella sp. Pv2, Rahnella sp. Pv3, Rahnella sp. Pv4, Rahnella sp. Pv5, Pantoea agglomerans Pv6, Staphylococcus sp. Pv7, Micrococcus luteus Pv8, and Rahnella sp. Pv9. The highest insecticidal activity against larvae and adults was obtained from M. luteus Pv8 with 50 and 40 % mortalities within 10 days after treatment, respectively. Extracellular enzyme activity of the bacterial isolates such as amylase, proteinase, lipase, cellulose, and chitinase was also determined. Consequently, our results show that M. luteus Pv8 might be a good candidate as a possible microbial control agent against P. versicolora and were discussed with respect to biocontrol potential of the bacterial isolates.     

Development of a capillary isoelectric focusing immunoassay to measure DJ-1 isoforms in biological samples

We report on the development of a novel assay protocol for the separation and detection of charge isoforms of DJ-1 in biological samples by automated capillary isoelectric focusing followed by immunological detection. DJ-1 (PARK7) is considered as a biomarker candidate for Parkinson’s disease and may potentially support the differentiation of clinical subtypes of the disease. The new method allows for separation and subsequent relative quantitative comparison of different isoforms of DJ-1 in biological samples. The assay was successfully applied to the analysis of DJ-1 isoform patterns in brains from mice subjected to normal or high-fat diet and revealed statistically significant group differences. Furthermore, in a pooled and concentrated sample of human cerebrospinal fluid that was depleted of albumin and immunoglobulin G, four different charge variants of DJ-1 could be detected. Taken together, the capillary isoelectric focusing immunoassay for DJ-1 represents a promising tool that may ultimately serve in clinical biomarker studies.     

Immobilization of fungal nitrilase and bacterial amidase – two enzymes working in accord

A nitrilase from Aspergillus niger and an amidase from Rhodococcus erythropolis co-immobilized on a 1-mL Butyl Sepharose column were used for the hydrolysis of 4-cyanopyridine into isonicotinic acid. The former enzyme converted the nitrile into the acid:amide mixture (molar ratio ca. 3:1), while the latter enzyme hydrolyzed the amide by-product. Therefore, the ratio of amide in the total product decreased to about 5%. Sodium sulfate was used as a component of the elution buffer, as the commonly used ammonium sulfate (0.8 M) acted as an amidase inhibitor. The hydrolysis of 4-cyanopyridine by a nitrilase from F. solani gave isonicotinic acid and isonicotinamide at a molar ratio of about 98:2. When using this enzyme and the amidase immobilized on two columns operated in tandem, the percentage of isonicotinamide in total product decreased to <0.2%.     

Vegetative Compatibility,Pathogenicity and Virulence Diversity of Fusarium oxysporum f. sp. melongenae Recovered from Eggplant

Fusarium oxysporum (Schlechtend.: Fr.) f. sp. melongenae (Fomg) recovered from symptomatic eggplants from five eggplant‐growing areas in Turkey, including the south, west, north‐west, north and south‐east regions. The objective of this study was to investigate the genetic diversity of the Fomg isolates from different geographical location by pathogenicity and VCG tests. Three hundred and seventy‐four Fomg isolates were classified as highly virulent, virulent, moderately virulent and low virulent through pathogenicity assays. No correlation was observed between virulence of Fomg isolates and their locations. The nitrate non‐utilizing mutants (nit) were generated as nit1, nit3 and NitM, based on phenotyping of Fomg growth characteristics of the Fomg isolates on diagnostic media with various sources of nitrogen. The majority of nit mutants (39.4%) recovered were nit1 from minimal medium (MM) containing of 2.0% potassium chlorate (MMC). The most of Fomg isolates were identified as heterokaryon self‐compatible (HSC) based on their ability to form a stable heterokaryon, while four isolates were classified as heterokaryon self‐incompatible (HSI). A large amount of Fomg isolates were vegetatively compatible and assigned as members of the same VCG, whereas nit mutants of 10 Fomg isolates that did not complement with tester strains only paired by themselves (HSC), these isolates were termed vegetative incompatible (vic). The complementation of 33 isolates with tester strains was slow and quite weak, but not paired with themselves even though they are HSC. About 96.3% of the Fomg isolates were assigned to VCG 0320, while the remaining 3.7% were classified as vegetative incompatible group.     

Fluorescent rhodanine-3-acetic acids visualize neurofibrillary tangles in Alzheimer’s disease brains

There is a high demand for the development of an imaging agent for neurofibrillary tangles (NFTs) detection in Alzheimer’s diagnosis. In the present study, a series of rhodanine-3-acetic acids was synthesized and evaluated for fluorescence imaging of NFTs in brain tissues of AD patients. Five out of seven probes have shown excellent binding affinity to NFTs over amyloid plaques in the Thiazine red R displacement assay. However, the selectivity in this in vitro assay is not confirmed by the histopathological evaluation, which indicates significant differences in the binding sites in the assays. Probe 6 showed binding affinity (IC₅₀ = 19 nM) to tau aggregates which is the highest among this series. Probes 2, 3, 4 and 5 display IC₅₀ values of lower than 100 nM to tau aggregates to displace Thiazine red R. Evaluation of the cytotoxicity of these five probes with human liver carcinoma cells revealed that these compounds excert negligible cytotoxicity. The in vivo studies with zebrafish embryos confirmed negligible cytotoxicity at 24 and 72 h post fertilization.     

The impact of sleep duration on frailty in community-dwelling Turkish older adults

Sleep and Biological Rhythms - The aim of this study was to examine the association between sleep duration and frailty in community-dwelling Turkish older adults and to determine whether this...     

Oxidative and nitrative alpha‐synuclein modifications and proteostatic stress: implications for disease mechanisms and interventions in synucleinopathies

Alpha‐synuclein (ASYN) is a major constituent of the typical protein aggregates observed in several neurodegenerative diseases that are collectively referred to as synucleinopathies. A causal involvement of ASYN in the initiation and progression of neurological diseases is suggested by observations indicating that single‐point (e.g., A30P, A53T) or multiplication mutations of the gene encoding for ASYN cause early onset forms of Parkinson's disease (PD). The relative regional specificity of ASYN pathology is still a riddle that cannot be simply explained by its expression pattern. Also, transgenic over‐expression of ASYN in mice does not recapitulate the typical dopaminergic neuronal death observed in PD. Thus, additional factors must contribute to ASYN‐related toxicity. For instance, synucleinopathies are usually associated with inflammation and elevated levels of oxidative stress in affected brain areas. In turn, these conditions favor oxidative modifications of ASYN. Among these modifications, nitration of tyrosine residues, formation of covalent ASYN dimers, as well as methionine sulfoxidations are prominent examples that are observed in post‐mortem PD brain sections. Oxidative modifications can affect ASYN aggregation, as well as its binding to biological membranes. This would affect neurotransmitter recycling, mitochondrial function and dynamics (fission/fusion), ASYN's degradation within a cell and, possibly, the transfer of modified ASYN to adjacent cells. Here, we propose a model on how covalent modifications of ASYN link energy stress, altered proteostasis, and oxidative stress, three major pathogenic processes involved in PD progression. Moreover, we hypothesize that ASYN may act physiologically as a catalytically regenerated scavenger of oxidants in healthy cells, thus performing an important protective role prior to the onset of disease or during aging.