Fermented Biomass of Arthrospira platensis as a Potential Food Ingredient.

Lactic acid fermentation (LAF) is known to improve nutritional properties and functionality and to extend the shelf life of foods. We studied the LAF of Arthrospira platensis as the sole substrate using Lactobacillus plantarum as the starter culture. Fermented (FB) and non-fermented broth (NFB) were analysed by means of pH, lactic acid bacteria (LAB) count, lactic acid concentration, microbiological safety, and nutritional composition. Additionally, water and ethanol extracts were prepared on which total phenolic content, DPPH radical scavenging activity, and cellular antioxidant activity were determined. The maximum increase in LAB count and lactic acid concentration and drop in pH was observed in the first 24 h of fermentation. Total phenolic content and DPPH radical scavinging activity of ethanol extracts increased after fermentation compared with NFB. Ethanol extracts of FB have been shown as a potential source of antioxidants, which efficiently lowered oxidation level in the cells of yeast Saccharomyces cerevisiae, as well as the oxidative damage of lipids. Additionally, the level of non-protein nitrogen increased, indicating higher protein bioavailability, and fat content decreased in comparison with NFB. No presence of pathogenic bacteria and low pH indicate enhancement of FB microbiological stability. Therefore, inclusion of fermented A. platensis into food products could lead to added-value foods based on microalgae.

Neuroprotective Properties of Food-Borne Polyphenols in Neurodegenerative Diseases.

Fruits and vegetables are the richest source of polyphenols in the regular human diet [...].

Waste streams in onion production: Bioactive compounds, quercetin and use of antimicrobial and antioxidative properties.

Onion production generates abundant waste with high contents of bioactive compounds. These might have several beneficial functional properties for fortification of foods. To understand the variety and potential for further use, we examined various parts of the plants (edible/inedible waste/outer skin of onion), as well as extraction in water/ethanol and by shaking/sonication. Quercetin content and antioxidant capacity were initially determined for extracts of edible and waste parts of red, yellow and white onions, and red shallots. Ethanol extracts of the waste fraction had the highest quercetin content and antioxidant capacity. Except white onion, which contained no quercetin, the dried waste ethanol extracts contained up to 15 mg quercetin g-1 and had an antioxidant capacity of nearly 40 mg Trolox equivalents g-1. Furthermore, the dried skin ethanol extract of yellow onion, which is commercially the most available fraction, contained 8 mg quercetin g-1, with antioxidant capacity of 25 mg Trolox equivalents g-1 and high antimicrobial activity. Dried yellow onion skin showed good stability for the quercetin content under various storage conditions (4, 25, 37, 40 °C; dark/light; dry/moist air/in water). Bacteria, bacterial spores, yeast and mould counts remained unchanged for dried onion skin over 5 days under storage conditions that can promote food spoilage, indicating exceptional microbial stability. Finally, two different applications are demonstrated for dried yellow onion skin: tablets for home use (tablets as more convenient form of storage and for simple dosing in cooking), and a stabilisation additive (prolonged shelf-life of olive oil). Both represent efficient and straightforward approaches through waste prevention and food fortification.

In Vitro Comparison of the Bioactivities of Japanese and Bohemian Knotweed Ethanol Extracts.

Knotweed is a flowering plant that is native to temperate and subtropical regions in the northern hemisphere. We evaluated Japanese (Reynoutria japonica Houtt.) and Bohemian (Fallopia x bohemica) knotweed rhizome and flower ethanol extracts and compared them in terms of their biological activities. The specific polyphenols were identified and quantified using HPLC/DAD, and the antioxidant activity was determined using 2,2-diphenly-1-picrylhydrazyl (DPPH) and cellular antioxidant capacity assays. The anticancer activity was evaluated as the difference between the cytotoxicity to cancer cells compared with control cells. The antimicrobial activity was determined using bacteria and yeast. The antidiabetic activity was tested as the ability of the extracts to inhibit α-amylase. Both rhizome extracts were sources of polyphenols, particularly polydatin and (-)-epicatechin; however, the cellular assay showed the highest antioxidant capacity in the flower extract of F. bohemica. The PaTu cell line was the least sensitive toward all knotweed extracts. The flower extracts of both species were less toxic than the rhizomes. However, the activity of the tested extracts was not specific for cancer cells, indicating a rather toxic mode of action. Furthermore, all used extracts decreased the α-amylase activity, and the rhizome extracts were more effective than the flower extracts. None of the extracts inhibited bacterial growth; however, they inhibited yeast growth. The results confirmed that rhizomes of Reynoutria japonica Houtt. could become a new source of bioactive compounds, which could be used for the co-treatment of diabetes and as antifungal agents.

Enhanced Yield of Bioactivities from Onion (Allium cepa L.) Skin and Their Antioxidant and Anti-α-Amylase Activities.

There is increasing concern for reduction of the ecological impacts of industrial waste caused by fruits and vegetables. To reduce costs of onion waste disposal while obtaining value-added products, onion skin can be used to extract quercetin, a natural flavonoid with antioxidant, anti-inflammatory and anti-cancer effects. The aim was to optimize quercetin extraction from brown onion (Allium cepa L.) skin through investigation of the effects of different parameters on quercetin yield. Operational parameters for conventional maceration extraction and for ultrasound-assisted extraction were compared: solvent type, mass-to-liquid ratio, extraction time and temperature. Antioxidant capacity was determined using DPPH· radical scavenging assays and quercetin yield using HPLC/DAD. Anti-α-amylase activity of onion skin extracts was investigated using α-amylase inhibition assays. Optimal extraction conditions of quercetin from onion skin were obtained with maceration extraction, 50% ethanol, 1:100 mass-to-liquid ratio, 25 °C, for 15 min. Under these conditions, the antioxidant capacity (expressed as quercetin equivalents) was 18.7 mg/g and the mass fraction of quercetin was 7.96 mg/g. The onion skin extracts showed a dose-dependent relationship between dry extract concentration and α-amylase inhibition, which confirms that this onion skin extract can be considered as an anti-diabetes agent.

An Overview of Crucial Dietary Substances and Their Modes of Action for Prevention of Neurodegenerative Diseases.

Neurodegenerative diseases, namely Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis, Huntington's disease, and multiple sclerosis are becoming one of the main health concerns due to the increasing aging of the world's population. These diseases often share the same biological mechanisms, including neuroinflammation, oxidative stress, and/or protein fibrillation. Recently, there have been many studies published pointing out the possibilities to reduce and postpone the clinical manifestation of these deadly diseases through lifelong consumption of some crucial dietary substances, among which phytochemicals (e.g., polyphenols) and endogenous substances (e.g., acetyl-L-carnitine, coenzyme Q10, n-3 poysaturated fatty acids) showed the most promising results. Another important issue that has been pointed out recently is the availability of these substances to the central nervous system, where they have to be present in high enough concentrations in order to exhibit their neuroprotective properties. As so, such the aim of this review is to summarize the recent findings regarding neuroprotective substances, their mechanisms of action, as well as to point out therapeutic considerations, including their bioavailability and safety for humans.

Polyphenols from Food and Natural Products: Neuroprotection and Safety.

Polyphenols are naturally occurring micronutrients that are present in many food sources. Besides being potent antioxidants, these molecules may also possess anti-inflammatory properties. Many studies have highlighted their potential role in the prevention and treatment of various pathological conditions connected to oxidative stress and inflammation (e.g., cancer, and cardiovascular and neurodegenerative disorders). Neurodegenerative diseases are globally one of the main causes of death and represent an enormous burden in terms of human suffering, social distress, and economic costs. Recent data expanded on the initial antioxidant-based mechanism of polyphenols' action by showing that they are also able to modulate several cell-signaling pathways and mediators. The proposed benefits of polyphenols, either as protective/prophylactic substances or as therapeutic molecules, may be achieved by the consumption of a natural polyphenol-enriched diet, by their use as food supplements, or with formulations as pharmaceutical drugs/nutraceuticals. It has also been proved that the health effects of polyphenols depend on the consumed amount and their bioavailability. However, their overconsumption may raise safety concerns due to the accumulation of high levels of these molecules in the organism, particularly if we consider the loose regulatory legislation regarding the commercialization and use of food supplements. This review addresses the main beneficial effects of food polyphenols, and focuses on neuroprotection and the safety issues related to overconsumption.

Potential for brain accessibility and analysis of stability of selected flavonoids in relation to neuroprotection in vitro.

Natural food sources constitute a promising source of new compounds with neuroprotective properties, once they have the ability to reach the brain. Our aim was to evaluate the brain accessibility of quercetin, epigallocatechin gallate (EGCG) and cyanidin-3-glucoside (C3G) in relation to their neuroprotective capability. Primary cortical neuron cultures were exposed to oxidative insult in the absence and presence of the selected compounds, and neuroprotection was assessed through evaluation of apoptotic-like and necrotic-like cell death. The brain accessibility of selected compounds was assessed using an optimised human blood-brain barrier model. The blood-brain barrier model was crossed rapidly by EGCG and more slowly by C3G, but not by quercetin. EGCG protected against oxidation-induced neuronal necrotic-like cell death by ~40%, and apoptosis by ~30%. Both quercetin and C3G were less effective, since only the lowest quercetin concentration was protective, and C3G only prevented necrosis by ~37%. Quercetin, EGCG and C3G effectively inhibited α-synuclein fibrillation over the relevant timescale applied here. Overall, EGCG seems to be the most promising neuroprotective compound. Thus, inclusion of this polyphenol in the diet might provide an affordable means to reduce the impact of neurodegenerative diseases.

The effect of tyrosine residues on α-synuclein fibrillation.

Aggregation of the intrinsically disordered protein α-synuclein into ordered amyloid fibrils is implicated in the pathogenesis of Parkinson's disease. To unravel the role of Tyr residues in α-synuclein fibrillation, we prepared recombinant N-terminal (Y39A) and C-terminal (Y(125,133,136)A) mutants of α-synuclein and examined their fibrillation propensities by thioflavin T and 1-anilinonaphthalene-8-sulfonate (ANS) fluorescent probes, SDS-PAGE and atomic force microscopy. We demonstrate that in contrast to wild-type α-synuclein, both mutants show large, but comparable delays in the fibrillation process and exhibit enhanced hydrophobicity during fibril-like assembly. Both Tyr mutants form fibril-like structures after prolonged incubation periods, which are morphologically distinct from those of the wild-type protein. Our results suggest that the N-terminal and C-terminal Tyr residues of α-synuclein are important primarily for the initiation of the fibrillation process.

Application of optimized chemiluminescence assay for determination of the antioxidant capacity of herbal extracts.

A chemiluminescence (CL) assay for the determination of antioxidant capacity (AOC) has been optimized and applied to analyses of herbal extracts in the present study. The optimal concentrations of reagents (luminol, H2O2, horseradish peroxidase) have been determined, as well as the optimal reaction conditions (wavelength, pH, temperature, sample volume). All of the measurements were performed at the emission maximum of the oxidized form of luminol (425 nm). The optimal concentrations of the reagents were determined as follows: 1.6 mmol/L luminol, 7.5 mmol/L H2O2 and 0.14 U/mL horseradish peroxidase activity in the reaction mixture. Analyses were carried out in phosphate buffer, pH 7.4, at room temperature. With the optimized CL assay, the AOCs of various water and methanol herbal extracts were determined (dog rose hips, plantain leaves and coltsfoot and thyme flowers) and the results were compared to those obtained by other classical methods for the evaluation of antioxidants. Strong correlations (r > 0.9) with the Folin-Ciocalteau assay and the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH)(●) assay are confirmed, although there is no correlation between AOC and the concentration of ascorbic acid in the samples analysed. This optimized CL assay is simple, rapid and reliable, and it represents a good alternative to classical methods (Folin-Ciocalteau, DPPH(●)) for the determination of AOC of herbal extracts and other food samples.

Photothermal bioanalytical methods for pesticide toxicity testing.

This paper describes bioanalytical methods and biosensors which rely on cholinesterase (ChE) inhibition and can be used to detect and test the toxicity of organophosphate (OP) and carbamate pesticides. Particular attention is given to the combined use of these methods and photothermal detection that has recently led to improved sensitivity and increased sample throughput of ChE bioanalytical assay. Following a rapid and simple sample preparation procedure, this assay can detect organophosphate pesticides such as paraoxon in the sub ng/mL concentration range. The AChE bioanalytical method demonstrated different sensitivity to various pesticides, which correlated well with pesticide toxicity expressed as LD50 for rats. Similarly, the same pesticide yielded different ChE inhibition in different organisms. This opens the possibility of applying these bioanalytical methods to evaluate the acute toxicity of OP compounds or of environmental samples to particular organisms.

Detection of organophosphate and carbamate pesticides in vegetable samples by a photothermal biosensor.

Previously developed photothermal biosensor was optimised by determining the most suitable enzyme substrate (acetylthiocholine iodide) and the optimal carrier buffer (0.05 M phosphate buffer, pH 8.0). Excitation laser operating at 488 nm and 120 mW power provided the highest biosensor sensitivity. The biosensor was tested for detection of toxic organophosphate and carbamate compounds present in samples of salad, iceberg lettuce, and onion. Sufficient sensitivities to different pesticides (carbofuran, propamocarb, oxydemeton-methyl and parathion-ethyl) were achieved without time-consuming sample preparation procedures. The results show good agreement with the concentrations of pesticides determined with standard GC-MS detection method. The developed photothermal biosensor offers new low cost means to detect low concentrations of pesticides in vegetable samples with high throughput and little or no sample pretreatment.

Validation of different commercially available cholinesterases for pesticide toxicity test.

A systematic study of different commercially available cholinesterases (AChEs from electric eel, human erythrocytes, bovine erythrocytes and BuChE from horse serum) for the FIA determination of some frequently used organophosphate (paraoxon, oxydemeton-methyl, triazophos, diazionon) and carbamate (carbofuran, propoxur) pesticides was carried out. Responses of the previously developed photothermal FIA system were found to be dependent on the origin of cholinesterases and properties of tested pesticides. The highest sensitivity was obtained with electric eel AChE and the lowest sensitivity with horse serum BuChE. The LOD values for investigated pesticides correlate with acute toxicities expressed as LD50 (oral, rat). The presented FIA system could serve as an alternative screening test to evaluate the toxicity of different environmental samples, new cholinesterase inhibiting pesticides or other products (e.g. nerve gases).