Antiradical, chelating and antioxidant activities of hydroxamic acids and hydroxyureas

An evaluation of quartz as a component of respirable coal dust

The rising cases of coal worker's pneumoconiosis since the early 2000s have driven research into respirable coal dust. Prolonged quartz dust exposure is deemed to be the primary cause of the resurgence in pneumoconiosis. This study examines how quartz present in coals of various ranks produces hydroxyl radicals (•OH), a reactive oxygen species linked to particle toxicity. This study evaluates the ability of safe chemical additives to reduce •OH production of the coal-quartz samples at various pH levels. Promising chemicals were investigated in different solutions, including tap and process waters and simulated lung fluid (SLF). We combined insights from electrokinetic measurements, infrared and X-ray photoelectron spectroscopies, and ab initio atomistic simulations to study the quartz particle surfaces. The study also explored how surface aging impacts quartz •OH production. The results reveal that •OH generation of the quartz varies and is enhanced by iron contamination, as also confirmed by ab initio simulations. Iron also enhances hydroxamic acid adsorption, leading to stronger interaction of the reagent on the quartz surface. Fresh quartz surfaces are particularly prone to generating more •OH in alkaline conditions. Carboxymethyl cellulose was notably effective in inhibiting quartz •OH by about 91 % at pH 7 in deionized water. The production of •OH was minimal in SLF compared to other tested solutions. The negative charge on quartz surface in various aqueous solutions was found to impact •OH generation. Quartz surface aging results in a gradual decrease in •OH generation due to the decay of surface siloxyl radicals.

Phenylacetyl-/Trolox- Amides: Synthesis, Sigma-1, HDAC-6, and Antioxidant Activities

In search of novel multi-mechanistic approaches for treating Alzheimer's disease (AD), we have embarked on synthesizing single small molecules for probing contributory roles of the following combined disease targets: sigma-1 (σ-1), class IIb histone deacetylase-6 (HDAC-6), and oxidative stress (OS). Herein, we report the synthesis and partial evaluation of 20 amides (i.e., phenylacetic and Trolox or 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid derivatives). Target compounds were conveniently synthesized via amidation by either directly reacting acyl chlorides with amines or condensing acids with amines in the presence of coupling agents 1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo [4,5-b] pyridinium 3-oxide hexafluorophosphate (HATU) or 1,1'-carbonyldiimidazole (CDI). Overall, this project afforded compound 8 as a promising lead with σ-1 affinity (Ki = 2.1 μM), HDAC-6 (IC50 = 17 nM), and antioxidant (1.92 Trolox antioxidant equivalents or TEs) activities for optimization in ensuing structure-activity relationship (SAR) studies.

Extraction Optimization, Antioxidant, Cosmeceutical and Wound Healing Potential of Echinacea purpurea Glycerolic Extracts

Echinacea purpurea is a plant with immunomodulating properties, often used in topical preparations for treatment of small superficial wounds. In the presented study, the best conditions for ultrasound-assisted extraction of caffeic acid derivatives (caftaric and cichoric acid) (TPA-opt extract), as well as the conditions best suited for preparation of the extract with high radical scavenging activity (RSA-opt extract), from E. purpurea aerial parts were determined. A Box-Behnken design based on glycerol content (%, w/w), temperature (°C), ultrasonication power (W) and time (min) as independent variables was performed. Antioxidant, antiaging and wound healing effects of the two prepared extracts were evaluated. The results demonstrate that glycerol extraction is a fast and efficient method for preparation of the extracts with excellent radical scavenging, Fe²⁺ chelating and antioxidant abilities. Furthermore, the extracts demonstrated notable collagenase, elastase and tyrosinase inhibitory activity, indicating their antiaging properties. Well-pronounced hyaluronidase-inhibitory activities, with IC₅₀ values lower than 30 μL extract/mL, as well as the ability to promote scratch closure in HaCaT keratinocyte monolayers, even in concentrations as low as 2.5 μL extract/mL (for RSA-opt), demonstrate promising wound healing effects of E. purpurea. The fact that the investigated extracts were prepared using glycerol, a non-toxic and environmentally friendly solvent, widely used in cosmetics, makes them suitable for direct use in specialized cosmeceutical formulations.

New isolate from Salvinia molesta with antioxidant and urease inhibitory activity

Urease plays a significant role in the pathogenesis of urolithiasis pyelonephritis, urinary catheter encrustation, hepatic coma, hepatic encephalopathy, and peptic acid duodenal ulcers. Salvinia molesta was explored to identify new bioactive compounds with particular emphasis on urease inhibitors. The aqueous methanol extract was fractionated using solvents of increasing polarity. A series of column chromatography and later HPLC were performed on butanol extract. The structures of the resulting pure compounds were resolved using NMR (1D and 2D), infrared, and mass spectroscopy. The novel isolate was evaluated for antioxidant activity (using DPPH, superoxide anion radical scavenging, oxidative burst, and Fe⁺² chelation assays), anti-glycation behavior, anticancer activity, carbonic anhydrase inhibition, phosphodiesterase inhibition, and urease inhibition. One new glucopyranose derivative 6'-O-(3,4-dihydroxybenzoyl)-4'-O-(4-hydroxybenzoyl)-α/β-D-glucopyranoside (1) and four known glycosides were identified. Glycoside 1 demonstrated promising antioxidant potential with IC₅₀ values of 48.2 ± 0.3, 60.3 ± 0.6, and 42.1 ± 1.8 μM against DPPH, superoxide radical, and oxidative burst, respectively. Its IC₅₀ in the Jack bean urease inhibition assay was 99.1 ± 0.8 μM. The mechanism-based kinetic studies presented that compound 1 is a mixed-type inhibitor of urease with a K_i value of 91.8 ± 0.1 μM. Finally, molecular dynamic simulations exploring the binding mode of compound 1 with urease provided quantitative agreement between estimated binding free energies and the experimental results. The studies corroborate the use of compound 1 as a lead for QSAR studies as an antioxidant and urease inhibitor. Moreover, it needs to be further evaluated through the animal model, that is, in vivo or tissue culture-based ex-vivo studies, to establish their therapeutic potential against oxidative stress phosphodiesterase-II and urease-induced pathologies.

Radioprotective Role of Natural Polyphenols: From Sources to Mechanisms

The identification and development of radioprotective agents has emerged as a subject matter of research during recent years due to the growing usage of ionizing radiation in different areas of human life. Previous work on synthetic radioprotectors has achieved limited progress because of the numerous issues associated with toxicity. Compounds extracted from plants have potential to serve as lead candidates for developing ideal radioprotectors due to their low cost, safety and selectivity. Polyphenols are the most abundant and commonly dispersed group of biologically active molecules possessing broad range of pharmacological activities. Polyphenols have displayed efficacy for radioprotection during various investigations and can be administered at high doses with lesser toxicity. Detoxification of free radicals, modulating inflammatory responses, DNA repair, stimulation of hematopoietic recovery, and immune functions are the main mechanisms for radiation protection with polyphenols. Epicatechin, epigallocatechin-3-gallate, apigenin, caffeic acid phenylethylester, and silibinin provide cytoprotection together with the suppression of many pro-inflammatory cytokines owing to their free radical scavenging, anti-oxidant, and anti-inflammatory properties. Curcumin, resveratrol, quercetin, gallic acid, and rutin's radioprotective properties are regulated primarily by direct or indirect decline in cellular stress. Thus, polyphenols may serve as potential candidates for radioprotection in the near future, however, extensive investigations are still required to better understand their protection mechanisms.

Antihyperlipidemic and antioxidant properties of hydro-alcoholic extracts from Anogeissus leiocarpus (Combretaceae)

Anogeissus leiocarpus (Combretaceae) is a medicinal plant used in Togo to treat diabetes mellitus and others diseases. The present study was undertaken to evaluate the antihyperlipidemic and antioxidant activities of total extract and fractions of roots of Anogeissus leiocarpus.

The antihyperlipidemic activity of the total extract and the supernatant was performed in vivo by the fructose overload test in ICR mice. Antioxidant potential was determined in vitro by methods based on scavenging of DPPH∗, total antioxidant capacity and reducing power. After the screening, phenolic compounds and flavonoids were evaluated by the well–known colorimetric assay using respectively Folin–Ciocalteu reagent and aluminium chloride.

The results obtained showed that the total extract and the supernatant significantly reduced the serum and liver levels of triglycerides and hence the level of VLDL-Cholesterol compared to hyperlipidemic mice. In vitro the total extract and fractions had the ability to scavenge free radicals, to reduce metal and possessed strong total antioxidant activity. Phytochemical screening revealed the presence of polyphenols, flavonoids, alkaloids, tannins and saponosides in the extract and fractions. And the supernatant fraction contained more polyphenolic compounds than others.

From this study, it is concluded that the total extract and fraction of Anogeissus leiocarpus possessed strong antihyperlipidemic, antioxidant properties and were riched in polyphenols, which can be used in the treatment of diabetes mellitus’ complications. Hence, the supernatant fraction was the most biologically active.

Effect of the hydroxamate group in the antitumoral activity and toxicity toward normal cells of new copper(II) complexes

The synthesis, physico-chemical characterization and cytotoxicity of four copper(II) coordination complexes, i.e. [Cu(HBPA)Cl₂] (1), [Cu(BHA)₂] (2), [Cu(HBPA)(BHA)Cl] CH₃OH (3) and [Cu(HBPA)₂]Cl₂·4H₂O (4), are reported. HBPA is the tridentate ligand N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)amine and HBHA is the benzohydroxamic acid. The reaction between the HBHA and CuCl₂.2H₂O has resulted in the new complex (2) and the reaction between complex (1) and HBHA has resulted in the new complex (3). X-ray diffraction studies for complex (3) indicated the effective coordination of HBHA as BHA^-. Their cytotoxicity was evaluated against three human tumoral cell lines (Colo-205, NCI-H460 and U937) and PBMC (peripheral blood mononuclear cells), using the MTT cytotoxic assay. The results toward PBMC reveal that the new copper(II) complex (2) presents lower toxicity toward normal cells. Furthermore, complex (2) presents IC₅₀ values lower than cisplatin toward NCI-H460 and the best selectivity index obtained towards NCI-H460 (SI = 2.2) and U937 cell lines (SI = 2.0), as a result of the presence of two molecules of HBHA in its structure. Complex (3) presents IC₅₀ values lower than cisplatin toward NCI-H460, Colo-205 and comparable to cisplatin toward U937. The evaluation of the cell death type promoted by complexes (2) and (4) was investigated toward NCI-H460 revealing better results than the standard drug cisplatin, according to the Annexin V and propidium iodide (PI) labeling experiment. Based on the studies here performed, HBHA seems to be related to lower toxicity toward PBMC and HBPA is improving directly the cytotoxity.

Chemical Composition, Antioxidant, and α-Glucosidase-Inhibiting Activity of Aqueous and Hydroethanolic Extracts of Traditional Antidiabetics from Croatian Ethnomedicine

Type 2 diabetes (T2D) is a chronic disease with a growing prevalence worldwide. In addition to the conventional therapy, many T2D patients use phytotherapeutic preparations. In the present study, chemical composition, antioxidant, and α-glucosidase inhibiting activity of traditional antidiabetics from Croatian ethnomedicine (Achillea millefolium, Artemisia absinthium, Centaurium erythraea, Morusalba, Phaseolus vulgaris, Sambucus nigra, and Salvia officinalis) were assessed. The efficacy of water and 80% ethanol as extraction solvents for bioactive constituents was compared. HPLC analysis revealed that the prepared extracts were rich in phenols, especially rutin, ferulic, and chlorogenic acid. Antiradical (against DPPH and ABTS radicals), reducing (towards Mo6+ and Fe3+ ions), and enzyme inhibiting properties were in linear correlation with the content of phenolic constituents. Ethanolic extracts, richer in phenolic substances, showed dominant efficacy in those assays. Aqueous extracts, on the other hand, were better Fe2+ ion chelators and more active in the β-carotene linoleic acid assay. Extracts from S. officinalis and A. millefolium were particularly active antioxidants and α-glucosidase inhibitors. A. absinthium, another potent α-glucosidase inhibitor, contained chromium, a mineral that promotes insulin action. The investigated plants contained significant amounts of minerals useful in management of T2D, with negligible amounts of heavy metals deeming them safe for human use.

Green synthesized hydroxamic acid administered in high dose disrupts the antioxidant balance in the hepatic and splenic tissues of albino rats

Background

Hydroxamic acids are currently being used in diverse biological activities. We investigated the effect of hydroxamic acid, synthesized from Cyperus esculentus seeds, on the antioxidant status of the liver, spleen, and kidney of Wistar rats.

Methods

Twenty male rats were randomly divided into three treatment groups using hydroxamic acid at doses of 5, 15, and 50 mg/kg and a control group using distilled water. Rats were sacrificed 24 h after a seven-day repeated oral dosing. After that, the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST), and the levels of glutathione (GSH) and malondialdehyde (MDA) were investigated in the organs.

Results

Our data showed that MDA levels remained unaltered in the liver, spleen, and kidney. However, it was found that hydroxamic acid at the dose of 50 mg/kg significantly increased SOD activity but depleted CAT, GPx activities and GSH levels in the liver when compared to the control groups. In splenic tissue, SOD activity and GSH levels were significantly diminished. Contrarily, in the kidney, treatment of rats with 50 mg/kg hydroxamic acid did not affect SOD activity, but GPx activity was increased while GST activity was decreased when compared to the controls.

Conclusion

Overall, hydroxamic acid may enhance antioxidant enzyme activities in the liver and kidney. However, caution is required at higher doses to forestall oxidative stress in the hepatic and splenic tissues.

In vitro antioxidant and enzyme inhibitory properties of the n-butanol fraction of Senna podocarpa (Guill. and Perr.) leaf

Background This study evaluates the antioxidant activity and enzyme inhibitory properties of the n-butanol fraction of Senna podocarpa leaves on α-amylase, α-glucosidase, acetylcholinesterase (AChE), butyrylcholinesterase (BChE), tyrosinase, arginase, phosphodiesterase 5 (PDE-5), and angiotensin converting enzyme (ACE). Methods The total phenol and flavonoids, iron (Fe) chelation, and 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) free radical scavenging were used to determine the antioxidant activity, and the inhibitory activities of α-glucosidase, α-amylase, AChE, BChE, tyrosinase, arginase, PDE-5 and ACE were also assessed. Results The n-butanol fraction of S. podocarpa shows high total phenol and total flavonoid contents. The n-butanol fraction of S. podocarpa leaves also chelates Fe2+ and ABTS radicals. The n-butanol fraction of S. podocarpa leaves also inhibited α-glucosidase, α-amylase, AChE, BChE, tyrosinase, arginase, PDE-5, and ACE at the concentration tested. Chromatographic analysis displayed the presence of β-elemene, phytol and caryophyllene oxide chrysophanol, 3-oxo-methyl ester, α-humulene, β-caryophyllene, rhein, emodin, and α-copaene. Conclusions Hence, the n-butanol fraction of S. podocarpa leaves demonstrates encouraging feat in controlling and/or managing cognitive dysfunction such as Alzheimer's disease and also hypertension, diabetes, erectile dysfunction, endothelial dysfunction, and hyperpigmentation.

Glycerolic Licorice Extracts as Active Cosmeceutical Ingredients: Extraction Optimization, Chemical Characterization, and Biological Activity

A green ultrasound-assisted extraction (UAE) method using glycerol/water mixtures for extraction of licorice (Glycyrrhiza glabra) bioactive constituents was developed in this study. The response surface method, according to the Box-Behnken design, was employed to optimize the extraction parameters: glycerol concentration (X₁), temperature (X₂), and the amount of herbal drug used in the production (X₃). The responses were content of total phenols (TP), TP extraction efficiency (TPy) and the content of licorice characteristic constituents, glabridin (Gla) and isoliquiritigenin (Iso). Response surface analysis predicted the optimal extraction conditions for maximized amounts of TP, Tpy, Gla, and Iso. The extracts were prepared using the calculated conditions. The analysis of the selected constituents confirmed the validity of the model. Furthermore, biological activity of the extracts was tested. The results demonstrate that UAE using glycerol is a fast and efficient method for preparation of extracts with excellent radical scavenging, Fe²⁺ chelating and antioxidant activity. Furthermore, the observed notable tyrosinase and elastase inhibitory activity of the extracts, as well as their anti-inflammatory activity, indicate the anti-aging properties of the investigated extracts. The fact that the extracts were prepared using the safe, cosmetically active solvent, glycerol, makes them suitable for direct use in specialized cosmeceutical formulations.

Antioxidant Activities of Vaccinium vitis-idaea L. Leaves within Cultivars and Their Phenolic Compounds

Lingonberry leaves are the subject of numerous studies because of antioxidant properties, positive influence on the health and potential use in the prevention and treatment of chronic diseases. In this work, the radical scavenging, reducing, chelating activities, and phenolic composition of ten lingonberry leaves cultivars, one subspecies, and one variety were investigated. Furthermore, the antioxidant activity of individual phenolic compounds, that can be found in lingonberry leaves, were analyzed, and structure-activity relationship was determined. Wide diversity for phenolic profile and antioxidant properties of lingonberry leaves has been observed in the present material. Cultivars 'Kostromskaja rozovaja', 'Rubin', and Vaccinium vitis-idaea var. leucocarpum surpassed all others tested cultivars and lower taxa by contents of phenolic compounds and antioxidant activity. Leaves of lingonberry cultivars and lower taxa are rich in arbutin, flavonol glycosides, proanthocyanidins, and the latter were considered to be the major contributor to antioxidant properties of lingonberry leaves.

Methods for Hydroxamic Acid Synthesis

Substituted hydroxamic acid is one of the most extensively studied pharmacophores because of their ability to chelate biologically important metal ions to modulate various enzymes, such as HDACs, urease, metallopeptidase, and carbonic anhydrase. Syntheses and biological studies of various classes of hydroxamic acid derivatives have been reported in numerous research articles in recent years but this is the first review article dedicated to their synthetic methods and their application for the synthesis of these novel molecules. In this review article, commercially available reagents and preparation of hydroxylamine donating reagents have also been described.

Acetylcholinesterase Inhibition and Antioxidant Activity of N-trans-Caffeoyldopamine and N-trans-Feruloyldopamine

Phenolic acids and their derivatives found in nature are well-known for their potential biological activity. In this study, two amides derived from trans-caffeic/ferulic acid and dopamine were synthesized and characterized by Fourier-transform infrared spectroscopy (FTIR), mass spectrometry, proton and carbon-13 nuclear magnetic resonance spectroscopy. The compounds were tested for the inhibition of acetylcholinesterase (AChE) from Electrophorus electricus and for antioxidant activity by scavenging 2,2-diphenyl-1-pycrylhydrazyl free radical (DPPH^•) and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) radical cation (ABTS^•+), reducing ferric ions, and ferrous ions chelation. N-trans-Feruloyldopamine displayed the highest inhibitory effect on AChE with half-maximal inhibitory concentration (IC₅₀) values of 8.52 μM. In addition, an in silico study was done to determine the most favorable AChE cluster with the synthesized compounds. Further, these clusters were investigated for binding positions at the lowest free binding energy. Both synthesized hydroxycinnamates were found to be better antioxidants than the parent acids in in vitro tests applied. N-trans-Caffeoyldopamine showed the best antioxidant activity in the three tested methods—against non-biological stable free radicals IC₅₀ 5.95 μM for DPPH^•, 0.24 μM for the ABTS^•+ method, and for reducing power (ascorbic acid equivalent (AAE) 822.45 μmol/mmol)—while for chelation activity against Fe²⁺ ions N-trans-feruloyldopamine had slightly better antioxidant activity (IC₅₀ 3.17 mM).

Resolving the Role of Lipoxygenases in the Initiation and Execution of Ferroptosis

Lipoxygenases (LOXs) have been implicated as central players in ferroptosis, a recently characterized cell death modality associated with the accumulation of lipid hydroperoxides: the products of LOX catalysis. To provide insight on their role, human embryonic kidney cells were transfected to overexpress each of the human isoforms associated with disease, 5-LOX, p12-LOX, and 15-LOX-1, which yielded stable cell lines that were demonstrably sensitized to ferroptosis. Interestingly, the cells could be rescued by less than half of a diverse collection of known LOX inhibitors. Furthermore, the cytoprotective compounds were similarly potent in each of the cell lines even though some were clearly isoform-selective LOX inhibitors. The cytoprotective compounds were subsequently demonstrated to be effective radical-trapping antioxidants, which protect lipids from autoxidation, the autocatalytic radical chain reaction that produces lipid hydroperoxides. From these data (and others reported herein), a picture emerges wherein LOX activity may contribute to the cellular pool of lipid hydroperoxides that initiate ferroptosis, but lipid autoxidation drives the cell death process.

A hydroxamic acid–methacrylated collagen conjugate for the modulation of inflammation-related MMP upregulation

The selective covalent coupling of hydroxamic acid functions on to methacrylated type I collagen led to UV-cured networks with inherent MMP-modulating capability and enhanced proteolytic stability.

In vitro biological assessment of Homalium zeylanicum and isolation of lucidenic acid A triterpenoid

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Current investigation supports antioxidant, anti-diabetic activities of H. zeylanicum.

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Current investigation also supports anti-inflammatory activity of H. zeylanicum.

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The research successfully isolated and analysed structure of lucidenic acid A.

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Lucidenic acid A reported first time in the bark of H. zeylanicum.

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Lucidenic acid A produces a significant anti-inflammatory activity.

Homalium zeylanicum (Gardner) Benth. (Flacourtiaceae) is a medicinal plant useful in controlling rheumatism, inflammation and diabetes. The objective of this work evaluates in vitro antioxidant, antidiabetic, and antiinflammatory properties of hydroalcohol extract of bark of H. zeylanicum (HAHZ). It also describes isolation and structure determination of lucidenic acid A, which is the first report in this plant. In order to explain the role of antioxidant principles, DPPH, nitric oxide, hydroxyl, superoxide and metal chelating assays were performed. Antidiabetic and anti-inflammatory activities were investigated by quantifying α-amylase, α-glucosidase and protein denaturation inhibitory activities of HAHZ. Biochemical estimations were performed. The chemical structure of the triterpenoid was elucidated using ¹H, ¹³C NMR and high resolution-MS. IC₅₀ of DPPH, nitric oxide, hydroxyl, superoxide and metal chelating activities were of 36.23 ± 0.27, 40.11 ± 0.32, 35.23 ± 0.57, 43.34 ± 0.22 and 11.54 ± 0.08 μg/mL, respectively. IC₅₀ of α-amylase and α-glucosidase activities were 29.12 ± 0.54, and 18.55 ± 0.15 μg/mL. Total phenolic and total flavonoid contents were recorded at 233.65 mg/g GAE and 172.7 mg/g QE. Regarding kinetic behaviour, HAHZ showed competitive inhibition on α-glucosidase and mixed competitive inhibition on α-amylase. Lucidenic acid A was confirmed by spectroscopic studies. Anti-inflammatory activity of lucidenic acid A was determined by using protein denaturation assay with IC₅₀ 13 μg/mL but HAHZ showed 30.34 ± 0.13 μg/mL. Phenols and flavonoids could be attributed to inhibition of intestinal carbohydrases for anti-diabetic activities whereas triterpenoids could be responsible for anti-inflammatory activity of H. zeylanicum.

Chemical Composition, Antioxidant and α-Glucosidase-Inhibiting Activities of the Aqueous and Hydroethanolic Extracts of Vaccinium myrtillus Leaves

Vaccinium myrtillus (bilberry) leaf is traditionally used in southeastern Europe for the treatment of diabetes. In the present study, the ability of bilberry leaf extracts to inhibit carbohydrate-hydrolyzing enzymes and restore glutathione concentration in Hep G2 cells subjected to glucose-induced oxidative stress was investigated. A comprehensive analysis of the antioxidant activity of two bilberry leaf extracts was performed. The aqueous extract showed excellent total antioxidant and chelating activity. Its antioxidant activity in the β-carotene-linoleic acid assay was very good, reaching the activity of the antioxidant standard BHA (93.4 ± 2.3% vs. 95.1 ± 2.4%, respectively). The hydroethanolic extract (ethanol/H₂O, 8:2, v/v), on the other hand, was a better radical scavenger and Fe²⁺ reducing agent. Furthermore, the aqueous extract was able to efficiently increase glutathione concentration in Hep G2 cells subjected to glucose-induced oxidative stress and restore it to the levels observed in non-hyperglycaemic cells. The hydroethanolic extract strongly inhibited α-glucosidase, with the IC₅₀ statistically equal to the antidiabetic drug acarbose (0.29 ± 0.02 mg/mL vs. 0.50 ± 0.01 mg/mL, respectively). Phytochemical analysis revealed the presence of quercetin and kaemferol derivatives, as well as chlorogenic and p-coumaric acid. The study results indicate that V. myrtillus leaf may have promising properties as a supporting therapy for diabetes.

Cancer-associated fibroblasts enact field cancerization by promoting extratumoral oxidative stress

Histological inspection of visually normal tissue adjacent to neoplastic lesions often reveals multiple foci of cellular abnormalities. This suggests the presence of a regional carcinogenic signal that spreads oncogenic transformation and field cancerization. We observed an abundance of mutagenic reactive oxygen species in the stroma of cryosectioned patient tumor biopsies, indicative of extratumoral oxidative stress. Diffusible hydrogen peroxide (H₂O₂) was elevated in the conditioned medium of cultured skin epithelia at various stages of oncogenic transformation, and H₂O₂ production increased with greater tumor-forming and metastatic capacity of the studied cell lines. Explanted cancer-associated fibroblasts (CAFs) also had higher levels of H₂O₂ secretion compared with normal fibroblasts (FIBs). These results suggest that extracellular H₂O₂ acts as a field effect carcinogen. Indeed, H₂O₂-treated keratinocytes displayed decreased phosphatase and tensin homolog (PTEN) and increased Src activities because of oxidative modification. Furthermore, treating FIBs with CAF-conditioned medium or exogenous H₂O₂ resulted in the acquisition of an oxidative, CAF-like state. In vivo, the proliferative potential and invasiveness of composite tumor xenografts comprising cancerous or non-tumor-forming epithelia with CAFs and FIBs could be attenuated by the presence of catalase. Importantly, we showed that oxidatively transformed FIBs isolated from composite tumor xenografts retained their ability to promote tumor growth and aggressiveness when adoptively transferred into new xenografts. Higher H₂O₂ production by CAFs was contingent on impaired TGFβ signaling leading to the suppression of the antioxidant enzyme glutathione peroxidase 1 (GPX1). Finally, we detected a reduction in Smad3, TAK1 and TGFβRII expression in a cohort of 197 clinical squamous cell carcinoma (SCC) CAFs, suggesting that impaired stromal TGFβ signaling may be a clinical feature of SCC. Our study indicated that CAFs and cancer cells engage redox signaling circuitries and mitogenic signaling to reinforce their reciprocal relationship, suggesting that future anticancer approaches should simultaneously target ligand receptor and redox-mediated pathways.

Effect of Betula pendula Leaf Extract on α-Glucosidase and Glutathione Level in Glucose-Induced Oxidative Stress

B. pendula leaf is a common ingredient in traditional herbal combinations for treatment of diabetes in southeastern Europe. Present study investigated B. pendula ethanolic and aqueous extract as inhibitors of carbohydrate hydrolyzing enzymes, as well as their ability to restore glutathione concentration in Hep G2 cells subjected to glucose-induced oxidative stress. Phytochemical analysis revealed presence of rutin and other quercetin derivatives, as well as chlorogenic acid. In general, ethanolic extract was richer in phenolic substances than the aqueous extract. Furthermore, a comprehensive analysis of antioxidant activity of two extracts (determined by DPPH and ABTS radical scavenging activity, total antioxidant activity, and chelating activity as well as ferric-reducing antioxidant power) has shown that ethanolic extract was better radical scavenger and metal ion reductant. In addition, ethanolic extract effectively increased cellular glutathione levels caused by hyperglycemia and inhibited α-glucosidase with the activity comparable to that of acarbose. Therefore, in vitro research using B. pendula plant extracts has confirmed their antidiabetic properties.

In-Vitro dual inhibition of protein glycation, and oxidation by some Arabian plants

Background

Diabetes mellitus is a metabolic disorder of epidemic proportion, projected to become the major cause of morbidity and mortality in the world in future. Despite extensive research in understanding this disease at molecular level, and the discovery of new drugs, diabetes and its complications remain largely untreated. Many of the late diabetic complications are associated with the glycation of proteins in the body. Natural flora has long been a rich source for therapeutic agents, especially against diabetes. The present study deals with the anti-glycation properties of some medicinally important plants of Arabian region.

Methods

Twenty-six medicinal plants, commonly found in different regions of Arabian Peninsula, were evaluated for their protein anti-glycation activity by using BSA-MG glycation assay in-vitro. The extracts were incubated with BSA and MG at 37 °C for 9 days, each sample was then examined for the presence of fluorescence (λex 330 nm, and λem 420 nm), which represent the extent of protein glycation. Antioxidant activity was evaluated by using 1,1-diphenyl- 2-picrylhydrazyl (DPPH), iron chelation, and superoxide radical scavenging asaays.

Results

The data revealed that out of 26 medicinal plants, five plants viz. Sida cordifolia, Plumbago zeylanica, Tribulus terrestris, Glycyrrhiza glabra, and Rosa indica were active against the in-vitro protein glycation with IC₅₀ values between 0.408- 1.690 mg/mL. Among the active plants, Glycyrrhiza glabra L. was found to be the most potent (IC₅₀ = 0.408 ± 0.027 mg/mL), followed by Rosa indica (IC₅₀ = 0.596 ± 0.0179 mg/mL), and Sida cordifolia L. (IC₅₀ = 0.63 ± 0.009 mg/mL). The antioxidant potential of these plant extracts were also determined by using DPPH (2,2-diphenyl-1-picrylhydrazyl), iron chelation, and superoxide anion radical scavenging assays. Among five plants, Sida cordifolia exhibited a potent anti-oxidant activity in both DPPH and superoxide anion radical scavenging assays (IC₅₀ = 0.005 ± 0.0004, and 0.078 ± 0.002 mg/mL, respectively), followed by Rosa indica (IC₅₀ = 0.023 ± 0.0005 and 0.141 ± 0.003 mg/mL, respectively).

Conclusions

Protein glycation in hyperglycemic conditions involve oxidative changes. Therefore dual inhibition of protein glycation and oxidation are desirable properties in any test substance investigated for therapeutic purposes.

A dual-purpose silver nanoparticles biosynthesized using aqueous leaf extract of Detarium microcarpum: An under-utilized species

The need for green synthesis of emerging industrial materials has led to the biosynthesis of nanoparticles from plants to circumvent the adverse by-products of chemical synthesis. In this study, the leaf extract of Detarium mirocarpum Guill & Perr, a small tree belonging to the family Fabaceae (Legume), was used to synthesize silver nanoparticles (DAgNPs). DAgNPs were characterized using spectroscopic techniques (Ultraviolet-Visible spectroscopy and Fourier Transform Infrared spectroscopy) which showed hydroxyl and carbonyl functional groups to be responsible for their synthesis. DAgNPs were observed to be crystalline and spherical. The average size, determined by transmission electron microscopy (TEM) was 17.05nm. The antioxidant activity of DAgNPs ranked from moderate to good. The ability of DAgNPs to sense Hg(2+) and Fe(3+) ions in aqueous medium was also investigated. The quenching of the SPR peak at 430nm was used to monitor the toxic and heavy metal ions with linear ranges of 20-70µgmL(-1) and 10-40µgmL(-1) for Hg(2+) and Fe(3+), respectively. The limit of detection (LOD) and limit of quantification (LOQ) obtained for Hg(2+) was 2.05µgmL(-1) and 6.21µgmL(-1), respectively and for Fe(3+) was 5.01µgmL(-1) and 15.21µgmL(-1), respectively. The intra- and inter-day assessments of accuracy and repeatability gave relative errors less than 1% in all instances. DAgNPs can therefore provide a convenient method of sensing the toxic metals easily.

Antioxidant Activities of 4-Methylumbelliferone Derivatives

The synthesis of derivatives of 4-Methylumbelliferone (4-MUs), which are structurally interesting antioxidants, was performed in this study. The modification of 4-Methylumbelliferone (4-MU) by different reaction steps was performed to yield the target compounds, the 4-MUs. The 4-MUs were characterized by different spectroscopic techniques (Fourier transform infrared; FT-IR and Nuclear magnetic resonance; NMR) and micro-elemental analysis (CHNS). The in vitro antioxidant activity of the 4-MUs was evaluated in terms of their free radical scavenging activities against 2,2-diphenyl-1-picrylhydrazyl (DPPH), Nitric oxide radical scavenging activity assay, chelating activity and their (FRAP) ferric-reducing antioxidant power, which were compared with a standard antioxidant. Our results reveal that the 4-MUs exhibit excellent radical scavenging activities. The antioxidant mechanisms of the 4-MUs were also studied. Density Function Theory (DFT)-based quantum chemical studies were performed with the basis set at 3-21G. Molecular models of the synthesized compounds were studied to understand the antioxidant activity. The electron levels, namely HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital), for these synthesized antioxidants were also studied.

Radioprotective Agents: Strategies and Translational Advances

Radioprotectors are agents required to protect biological system exposed to radiation, either naturally or through radiation leakage, and they protect normal cells from radiation injury in cancer patients undergoing radiotherapy. It is imperative to study radioprotectors and their mechanism of action comprehensively, looking at their potential therapeutic applications. This review intimately chronicles the rich intellectual, pharmacological story of natural and synthetic radioprotectors. A continuous effort is going on by researchers to develop clinically promising radioprotective agents. In this article, for the first time we have discussed the impact of radioprotectors on different signaling pathways in cells, which will create a basis for scientific community working in this area to develop novel molecules with better therapeutic efficacy. The bright future of exceptionally noncytotoxic derivatives of bisbenzimidazoles is also described as radiomodulators. Amifostine, an effective radioprotectant, has been approved by the FDA for limited clinical use. However, due to its adverse side effects, it is not routinely used clinically. Recently, CBLB502 and several analog of a peptide are under clinical trial and showed high success against radiotherapy in cancer. This article reviews the different types of radioprotective agents with emphasis on the strategies for the development of novel radioprotectors for drug development. In addition, direction for future strategies relevant to the development of radioprotectors is also addressed.

Enzyme Inhibitory Properties, Antioxidant Activities, and Phytochemical Profile of Three Medicinal Plants from Turkey

We aimed to investigate the inhibitory potential of three medicinal plants (Hedysarum varium, Onobrychis hypargyrea, and Vicia truncatula) from Turkey against key enzymes involved in human pathologies, namely, diabetes (α-amylase and α-glucosidase), neurodegenerative disorders (tyrosinase, acetylcholinesterase, and butyrylcholinesterase), and hyperpigmentation (tyrosinase). The antioxidant potential, phenolic and flavonoid content of ethyl acetate, and methanolic and aqueous extracts were investigated using in vitro assays. The total antioxidant capacity (TAC), β-carotene/linoleic acid bleaching activity, 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH^•), 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS^•+), cupric ion reducing antioxidant capacity (CUPRAC), ferric reducing antioxidant power (FRAP), and metal chelating activity on ferrous ions were used to evaluate the antioxidant capabilities of the extracts. The half-maximal inhibitory concentrations (IC₅₀) of the extracts on cholinesterase, tyrosinase, and α-amylase were significantly higher than the references, galantamine, kojic acid, and acarbose, respectively. The half-maximal effective concentrations (EC₅₀) of the extracts on TAC, CUPRAC, and FRAP were significantly higher than trolox. The phenol and flavonoid contents of the plant extracts were in the range 20.90 ± 0.190–83.25 ± 0.914 mg gallic acid equivalent/g extract and 1.45 ± 0.200–39.71 ± 0.092 mg rutin equivalent/g extract, respectively. The plants were found to possess moderate antioxidant capacities and interesting inhibitory action against key enzymes.

Wild Edible Fruit of Prunus nepalensis Ser. (Steud), a Potential Source of Antioxidants, Ameliorates Iron Overload-Induced Hepatotoxicity and Liver Fibrosis in Mice

The antioxidant and restoration potentials of hepatic injury by Prunus nepalensis Ser. (Steud), a wild fruit plant from the Northeastern region of India, were investigated. The fruit extract (PNME) exhibited excellent antioxidant and reducing properties and also scavenged the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical (IC₅₀ = 30.92 ± 0.40 μg/ml). PNME demonstrated promising scavenging potency, as assessed by the scavenging of different reactive oxygen and nitrogen species. Moreover, the extract revealed an exceptional iron chelation capacity with an IC₅₀ of 25.64 ± 0.60 μg/ml. The extract induced significant improvement of hepatic injury and liver fibrosis against iron overload induced hepatotoxicity in mice in a dose-dependent manner, and this effect was supported by different histopathological studies. The phytochemical constitutions and their identification by HPLC confirmed the presence of purpurin, tannic acid, methyl gallate, reserpine, gallic acid, ascorbic acid, catechin and rutin. The identified compounds were investigated for their individual radical scavenging and iron chelation activity; some compounds exhibited excellent radical scavenging and iron chelation properties, but most were toxic towards normal cells (WI-38). On the other hand, crude PNME was found to be completely nontoxic to normal cells, suggesting its feasibility as a safe oral drug. The above study suggests that different phytochemicals in PNME contributed to its free radical scavenging and iron chelation activity; however, further studies are required to determine the pathway in which PNME acts to treat iron-overload diseases.

From α-nucleophiles to functionalized aggregates: exploring the reactivity of hydroxamate ion towards esterolytic reactions in micelles

Hydroxamate ions as α-nucleophiles for esterolytic reactions in water and micelles.

Metabolic variations, antioxidant potential, and antiviral activity of different extracts of Eugenia singampattiana (an endangered medicinal plant used by Kani tribals, Tamil Nadu, India) leaf

Eugenia singampattiana is an endangered medicinal plant used by the Kani tribals of South India. The plant had been studied for its antioxidant, antitumor, antihyperlipidemic, and antidiabetic activity. But its primary and secondary metabolites profile and its antiviral properties were unknown, and so this study sought to identify this aspect in Eugenia singampattiana plant through different extraction methods along with their activities against porcine reproductive and respiratory syndrome virus (PRRSV). The GC-MS analysis revealed that 11 primary metabolites showed significant variations among the extracts. Except for fructose all other metabolites were high with water extract. Among 12 secondary metabolites showing variations, the levels of 4-hydroxy benzoic acid, caffeic acid, rutin, ferulic acid, coumaric acid, epigallocatechin gallate, quercetin, myricetin, and kaempferol were high with methanol extract. Since the flavonoid content of methanol extracts was high, the antioxidant potential, such as ABTS, and phosphomolybdenum activity increased. The plants antiviral activity against PRRSV was for the first time confirmed and the results revealed that methanol 25 µg and 75 to 100 µg in case of water extracts revealed antiviral activity.

Antioxidant Potential of the Extracts, Fractions and Oils Derived from Oilseeds

The polyphenolic extracts and oils were obtained from ajwain, mustard, fenugreek and poppy seeds. The extracts were partitioned into acidic and neutral polyphenolic fractions and following estimation of total phenolics in the crude extract, acidic and neutral fractions and oil, all were analyzed for their DPPH (2,2-diphenyl-1-picrylhydrazyl) scavenging potential, ferric reducing ability and chelating power. The highest amount of polyphenols was found in ajwain (8330 ± 107), then in mustard seeds (2844 ± 56.00) and in fenugreek (1130 ± 29.00), and least in poppy seeds (937 ± 18.52). The higher amounts of polyphenols were estimated in neutral fraction compared to acidic (p < 0.05). % Inhibition of DPPH by the crude extract and fractions of all oilseeds was quite significant, being higher for acidic than neutral. The highest % DPPH inhibition was shown by ajwain extract than mustard > fenugreek and least by poppy seed extracts (p < 0.05). The reducing power and the chelating effect of the oilseeds followed the same order as DPPH, but higher % chelation was shown by neutral than acidic fraction (p < 0.05). Though low in polyphenols, the oil fractions were as strong antioxidants as the acidic one. Though oilseeds are used in very small quantity in food, they are potential sources of natural antioxidants and may replace synthetic ones.

Protective effect of flavonoids against reactive oxygen species production in sickle cell anemia patients treated with hydroxyurea

OBJECTIVE

The aim of this study was to evaluate the protective effects of quercetin, rutin, hesperidin and myricetin against reactive oxygen species production with the oxidizing action of tert-butylhydroperoxide in erythrocytes from normal subjects and sickle cell anemia carriers treated with hydroxyurea.

METHODS

Detection of intracellular reactive oxygen species was carried out using a liposoluble probe, 2',7'-dichlorfluorescein-diacetate (DCFH-DA). A 10% erythrocyte suspension was incubated with flavonoids (quercetin, rutin, hesperidin or myricetin; 30, 50, and 100 µmol/L), and then incubated with tert-butylhydroperoxide (75 µmol/L). Untreated samples were used as controls.

RESULTS

Red blood cell exposure to tert-butylhydroperoxide resulted in significant increases in the generation of intracellular reactive oxygen species compared to basal levels. Reactive oxygen species production was significantly inhibited when red blood cells were pre-incubated with flavonoids, both in normal individuals and in patients with sickle cell anemia. Quercetin and rutin had the highest antioxidant activity, followed by myricetin and hesperidin.

CONCLUSION

Flavonoids, in particular quercetin and rutin, showed better antioxidant effects against damage caused by excess reactive oxygen species characteristic of sickle cell anemia. Results obtained with patients under treatment with hydroxyurea suggest an additional protective effect when associated with the use of flavonoids.

Consequences and management of iron overload in sickle cell disease

The aims of this review are to highlight the mechanisms and consequences of iron distribution that are most relevant to transfused sickle cell disease (SCD) patients and to address the particular challenges in the monitoring and treatment of iron overload. In contrast to many inherited anemias, in SCD, iron overload does not occur without blood transfusion. The rate of iron loading in SCD depends on the blood transfusion regime: with simple hypertransfusion regimes, rates approximate to thalassemia major, but iron loading can be minimal with automated erythrocyte apheresis. The consequences of transfusional iron overload largely reflect the distribution of storage iron. In SCD, a lower proportion of transfused iron distributes extrahepatically and occurs later than in thalassemia major, so complications of iron overload to the heart and endocrine system are less common. We discuss the mechanisms by which these differences may be mediated. Treatment with iron chelation and monitoring of transfusional iron overload in SCD aim principally at controlling liver iron, thereby reducing the risk of cirrhosis and hepatocellular carcinoma. Monitoring of liver iron concentration pretreatment and in response to chelation can be estimated using serum ferritin, but noninvasive measurement of liver iron concentration using validated and widely available MRI techniques reduces the risk of under- or overtreatment. The optimal use of chelation regimes to achieve these goals is described.

The role of iron overload on oxidative stress in sickle cell anemia

Repeated blood transfusions in patients with sickle cell anemia (SCA) increases the risk of iron overload (IO), contributing to oxidative stress. Materials & methods: Blood samples of 15 SCA patients without IO (group 1) and 15 SCA patients with IO (group 2) and 30 healthy individuals were collected to investigate oxidative stress. IO was categorized using repeated measures of serum ferritin. The biomarkers evaluated were plasmatic malondialdehyde (MDA), nitrite and erythrocyte catalase. Results: MDA and nitrite were higher in group 2 than in group 1 and the healthy group (p < 0.001 for MDA and nitrite). Catalase presented lower in group 2 than group 1 and the healthy group (p < 0.001). We obtained a positive correlation between ferritin and MDA (r = 0.40; p < 0.02), and between ferritin and nitrite (r = 0359; p = 0.023). Conclusion: The results demonstrated that IO is an important risk factor for enhanced oxidative stress in SCA.

Anthraquinone profile, antioxidant and antimicrobial activity of bark extracts of Rhamnus alaternus, R. fallax, R. intermedia and R. pumila

The quantity of phenols, as well as antioxidant and antimicrobial activities, were investigated in bark of Rhamnus alaternus L., R. fallax Boiss., R. intermedia Steud. et Hochst., and R. pumila Turra from natural stands in Croatia. The most abundant anthraquinones in the investigated extracts were chrysophanol in R. alaternus (3.14 mg/g), emodin in R. pumila (0.339 mg/g), and physcion in R. fallax (2.70 mg/g) and R. intermedia (0.285 mg/g). The species exhibiting the highest antioxidant activity were R. fallax and R. pumila. A positive correlation was observed between total phenolic and flavonoid levels of the extracts and antioxidant activity in some of the assays. All species showed antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Candida albicans, Aspergillus niger and Microsporum gypseum with minimal inhibitory concentrations equal to or below 2.500 mg/mL. The results indicate that the investigated Rhamnus species are a source of anthraquinones and other phenols, which act as multifunctional antioxidants with antimicrobial activity.

Understanding the molecular interactions of different radical scavengers with ribonucleotide reductase M2 (hRRM2) domain: opening the gates and gaining access

We employed a combination of molecular docking and dynamics to understand the interaction of three different radical scavengers (SB-HSC21, ABNM13 and trimidox) with ribonucleotide reductase M2 (hRRM2) domain. On the basis of the observed results, we can propose how these ligands interact with the enzyme, and cease the radical transfer step from the di-iron center to TYR176. All the ligands alter the electron density over TYR176, -OH group by forming an extremely stable H-bond with either -NHOH group, or with phenolic hydroxyl group of the ligands. This change in electronic density disrupts the water bridge between TYR176, -OH and the di-iron center, which stops the single electron transfer process from TYR176, -OH to iron. As a consequence the enzyme is inhibited. Another interesting observation that we are reporting is the two stage gate keeping mechanism of the RR active site tunnel. We describe these as the outer Gate-1 controlled by ARG330, and the inner Gate-2 controlled by SER263, PHE240, and PHE236. We also observed a dynamic conformational shift in these residues, the incoming ligands can go through, and interact with the underlying TYR176, -OH group. From the study we found the active-site of hRRM2 is extremely flexible and shows a significant induced fit.