Stereoselective synthesis of procyanidin B3-3-O-gallate and 3,3″-di-O-gallate, and their abilities as antioxidant and DNA polymerase inhibitor

A simple method for the synthesis of procyanidin B3 substituted with a galloyl group at the 3 and 3″ position is described. Condensation of a benzylated catechin-3-O-gallate electrophile with a nucleophile, catechin and catechin-3-O-gallate, proceeded smoothly and stereoselectively to afford the corresponding dimer gallates, procyanidin B3-3-O-gallate and procyanidin B3-3,3″-di-O-gallate, in good yields. Further, their antioxidant activities on UV-induced lipid peroxide formation, DPPH radical scavenging activity and inhibitory activity of DNA polymerase were also investigated. Among three procyanidin B3 congeners (procyanidin B3, 3-O-gallate and 3,3″-di-O-gallate), the 3,3″-di-O-gallate derivative showed the strongest antioxidant and radical scavenging activity. Interestingly, the 3-O-gallate derivative was the strongest inhibitor of mammalian DNA polymerase with IC₅₀ value of 0.26 μM, although it showed the weakest antioxidant and radical scavenging activity. It became apparent that the presence of a galloyl group at the C-3 position in the proanthocyanidin oligomer was very important for biological activity, however, the antioxidant activity of these compounds was not parallel to the DNA polymerase inhibitory activity.     

Volatile constituents of Amomum argyrophyllum Ridl. and Amomum dealbatum Roxb. and their antioxidant,tyrosinase inhibitory and cytotoxic activities

The volatile components from fresh rhizomes and leaves of Amomum argyrophyllum Ridl. and Amomum dealbatum Roxb. were performed using HS-SPME and charac-terized by GC–MS. A total of 49, 47, 49, and 34 compounds were identified from the rhizomes and leaves of A. argyrophyllum and A. dealbatum, respectively. The major components were β-pinene, α-pinene, and o-cymene. The rhizome extracts exhibited total phenolic content of 2.9 ± 0.5 and 2.1 ± 0.6 mg gallic acid equivalents. The IC₅₀ values of DPPH and ABTS were 179.8 ± 3.9 µg/mL, 392.9 ± 2.6 µg/mL, 120.3 ± 2.5 µg/mL, and 328.6 ± 3.3 µg/mL, respectively. The FRAP values were 76.5 ± 7.8 and 84.9 ± 4.4 µM ascorbic acid equivalents. The extracts showed weak antibacterial activity and tyrosinase inhibitory activity of 69.0 ± 3.6 and 53.7 ± 7.4 mg kojic acid equivalents. The cytotoxicity effect was assessed with the MTT assay at 200 µg/mL. The extracts showed no toxicity. In addition, the anti-inflammatory properties of extracts were evaluated, and showed potential to inhibit nuclear factor-κB (NF-κB) activity.     

Ultrasound-assisted extraction of Cordyceps cicadae polyphenols: Optimization,LC-MS characterization,antioxidant and DNA damage protection activity evaluation

In this study, ultrasound-assisted extraction of polyphenols from C. cicadae was optimized by response surface methodology (RSM). The optimized conditions were determined as extraction time of 39 min, liquid-to-solid ratio of 1:29 g/mL, extraction temperature of 69 °C and ethanol concentration of 55% with a yield of 21.9 mg gallic acid equivalent/g dry weight. Four resins were used for polyphenol purification. D101 resin had the highest ratio of adsorption and was further applied in polyphenol purification test. A total of 19 different phenolic compounds were identified by LC-MS, including 12 phenolic acids and 7 organic acids. In addition, C. cicadae polyphenols displayed higher antioxidant activity in vitro and anti-aging activity of C. elegans in vivo. Lastly, C. cicadae polyphenols showed the potential to protect DNA from oxidative damage. Overall, our results suggest that polyphenols from C. cicadae may be considered as novel sources of anti-oxidation, anti-aging and recommended as reagents to protect DNA from oxidative damage in food and pharmaceutical industries.     

Characteristics and antioxidant activity of catechin-loaded calcium pectinate gel beads prepared by internal gelation

Catechin-loaded calcium pectinate gel beads prepared by internal gelation were characterized for their catechin entrapment efficiency and release behavior. The entrapment efficiency was higher when the beads were prepared with a lower catechin-to-pectin ratio, shorter gelling time, higher pectin concentration, and lower acetic acid concentration. The entrapment efficiency was much higher under all tested conditions, when the beads were prepared by internal gelation instead of external gelation. The catechin release was slower for the beads prepared with lower catechin-to-pectin ratio, longer gelling time, and higher concentrations of pectin and acetic acid in both simulated gastric and intestinal fluids. Antioxidant power of catechin was effectively maintained in alkaline simulated intestinal fluid when catechin was entrapped within the beads, compared to cases where it was not entrapped, indicating that the beads can protect catechin molecules from the alkaline environment and release them in a sustained fashion.     

Synthesis,spectral characterization,antioxidant, anticancer in vitro,and DNA cleavage studies of a series of ruthenium(II) complexes bearing Schiff base ligands

Ruthenium(II) complexes with 2-acetylpyridine-thiosemicarbazones (L¹–L⁴) were synthesized and characterized by analytical and spectral (FT-IR, UV–vis, NMR [¹H, ¹³C and ³¹P], and ESI-Mass) methods. Systematic biological investigations, free radical scavenging, anticancer activities, and DNA cleavage studies, were carried out for the complexes. Antioxidant studies showed that the complexes have significant antioxidant activity against DPPH, hydroxyl, nitric oxide radicals and hydrogen peroxide assay. The in vitro cytotoxicity of complexes against breast cancer (MCF-7) cell line was assayed showing high cytotoxicity with low IC₅₀ values indicating their efficiency in destroying the cancer cells even at very low concentrations. The DNA cleavage studies showed that the complexes efficiently cleaved DNA.     

A silver nanoparticles-catalyzed efficient three-component synthesis of polysubstituted 4H-chromenylphosphonates and their antioxidant activity

Abstract

A simple and efficient protocol for one-pot three-component synthesis of structurally diverse dialkyl 2-amino-3-cyano-4H-chromen-4-ylphosphonates from the condensation of salicylaldehydes, malononitrile, and trialkyl phosphite using silver nanoparticles as catalyst in ethanol at reflux has been developed. Selected new compounds were evaluated for their antioxidant activity by free radical screening using 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. Among the compounds employed, 5a, 5?b, and 5?h showed promising DPPH radical scavenging activities compared to the experimental standards at low concentration (100?µg/mL) after 24?h incubation.     

Fluorinated piperidine iminosugars and their N-alkylated derivatives: Synthesis,conformational analysis,immunosuppressive and glycosidase inhibitory activity studies

The fluorinated piperidine iminosugars 2a-4a and their N-octyl and N-decyl derivatives 2b,c-4b,c were synthesized from d-mannose/d-xylose using nucleophilic fluorination as the key step. The conformation of iminosugars 2/3, either ²C₅ or ⁵C₂, was assigned based on the ¹H NMR studies at different pH. Immunomodulatory activity of 2a,c-4a,c was examined using Mixed Lymphocyte Reaction (MLR) and B-cell assay. The N-alkylated fluorinated d-manno-iminosugars 3b/4b were found to be better immunosuppressive agents (IC₅₀?=?5–6?μM) on T-cells. The fluorinated iminosugar 3a/4a act as potent and selective inhibitors of β-glucosidase (IC₅₀?=?4–8?μM). The N-alkyl-iminosugars 4b-c were found to be moderate inhibitors of α-glucosidase (yeast) and α-galactosidase (coffee beans), respectively.     

Phytochemical screening,total phenolic content and antioxidant activity of Byrsonima species

The species of the Byrsonima genus (Malpighiaceae) have been used in folk medicine to treat gastrointestinal disorders, asthma and skin infections. In this study, the total phenolic content, antioxidant activity and phytochemical screening were carried out in polar extracts of Byrsonima coccolobifolia, Byrsonima verbascifolia and Byrsonima intermedia. The presence of tannins and flavonoids in the samples and high phenols content was observed. B. coccolobifolia and B. intermedia species showed the best results of antioxidant action. It was analysed the correlation between the methods, and there was a great correlation between phenolic content and antioxidant assay, showing that the phenolic substances contribute to the antioxidant activities of these plants.     

Synthesis of two novel mercaptobenzimidazole derivative Schiff bases and their in vitro antioxidant and enzyme inhibitory effects

In this study, 5-(2-hydroxy-4-methoxybenzylidenamino)-2-mercaptobenzimidazole and 5-(4-hydroxy-3-methoxybenzylidenamino)-2-mercaptobenzimidazole Schiff base compounds were synthesized and their structure were characterized with spectroscopic techniques, namely, 1H NMR, IR, and 13C NMR. In vitro ABTS, DPPH, CUPRAC, and FRAP tests were applied to calculate the antioxidant activities of the newly designed compounds. Beside, the enzyme inhibitory abilities of the mercaptobenzimidazole derivative Schiff base were assessed against the glutathione S-transferase (GST) enzyme. The K_i values were calculated as 20.06 ± 3.11 and 36.86 ± 6.17 μM, as well as the IC₅₀ values were calculated as 6.30 μM and 5.33 μM respectively. Besides, molecular docking interactions of the compounds with the GST target enzyme (PDB ID:5JCU) were estimated via Chimera and AutoDock Vina software. ?8.7 kcal/mol, and ?8.5 kcal/mol were calculated as best binding scores of compounds against the GST enzyme. Since the novel Schiff base, 5-(4-hydroxy-3-methoxybenzylidenamino)-2-mercaptobenzimidazole has a good potential in the GST inhibition, it should be subjected to the further pharmacological studies.     

Green synthesis of silver nanoparticles by bloom forming marine microalgae Trichodesmium erythraeum and its applications in antioxidant,drug-resistant bacteria,and cytotoxicity activity

In the present study, we developed an eco-friendly method of stable silver nanoparticles (AgNPs) production using the aqueous extract of Trichodesmium erythraeum. The biosynthesized AgNPs were characterized using UV–Vis spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Energy-Dispersive X-ray (EDX), and X-ray diffraction (XRD). The results affirmed that synthesized AgNPs were crystalline in nature, cubical in shape, and the average size of T. erythraeum silver nanoparticles (TENPs) was 26.5 nm. The antioxidant potential of synthesized AgNPs (500 µg/ml) was 77.01 ± 0.17% in DPPH, 67.5 ± 0.22% in Deoxy-ribose, 52.77 ± 0.42% in ABTS and 88.12 ± 0.26% in nitric oxide radical scavenging assays. The antibacterial results showed excellent inhibition against the clinical strains (Staphylococcus aureus and Proteus mirabilis) and drug-resistant bacterial strains such as E. coli (Amikacin^R), S. aureus (Tetracycline^R) and S. pneumoniae (Penicillin^R). The maximum anti-proliferative effect of TENPs was seen using 50 µg concentration against He La and MCF-7 cell lines, and IC₅₀ values were 25.0 ± 0.50 µg/ml and 30.0 ± 0.50 µg/ml, respectively, at 24 h.     

Biogenic synthesis of silver nanoparticles using Echium vulgare: Characterisation,quantitative analysis of bioactive compounds,antioxidant activity and catalytic degradation

Nanotechnology has a great significance owing to its large variety of applications. Silver nanoparticles (AgNPs@Ev) were produced using water extract of Echium vulgare aerial part by a simple, nontoxic, eco-friendly method. The spectroscopic study identified the structure of AgNPs@Ev. The absorption was detected as 460 nm by UV/Vis spectrophotometer. TEM analysis presented the morphology of nanostructures and particle size was calculated as 9.55 nm. XRD pattern showed the structure to be face-centered cubic unit cell. EDS analysis verified the presence of elemental silver. DLS and zeta potential analyses were executed by Zetasizer. The stability of nanostructures was revealed by the zeta potential analysis (−3.1 mV). The degradation performance of AgNPs@Ev on methylene blue was evaluated by UV/Vis spectrophotometer and 64% of methylene blue was degraded after 40 h. Quantitative analysis of natural compounds was performed by HPLC and isoquercitrin (1.32 mg/g extract), naringin (1.15 mg/g extract) were detected as major products. Antioxidant activity of extract and nanoparticles were achieved. AgNPs@Ev exhibited excellent DPPH, ABTS, and FRAP activities (IC₅₀, 6.8 μg/mL), (IC₅₀, 2.3 μg/mL), (5.3 μmol/g sample) respectively.     

Preparation of silybin 23-esters ability against LPO and and evaluation of their inhibitory DNA protective properties

Twelve 23-esterified silybin derivatives with different patterns of substituents such as aromatic and aliphatic groups (1-12) were designed and synthesized. The antioxidative properties of these compounds were evaluated. The modified silybin analogues exhibited improved inhibitory effects against rat liver homogenate lipid peroxidation compared to silybin, with exception of the trimethoxylated ester (5) and the aliphatic one (9). Compounds 3, 5, 7, 8 and 11 displayed their protective properties on DNA cleavage in a dose-dependent manner.     

Unprecedented stereoselective synthesis of 3-methylisoxazolidine-5-aryl-1,2,4-oxadiazoles via 1,3-dipolar cycloaddition and study of their in vitro antioxidant activity

The stereoselective 1,3-dipolar cycloaddition between allyl cyanide and a menthone-derived nitrone led to the desired isoxazolidine in good yield. Once the nitrile group transformed to an amidoxime group, the cyclocondensation of various aldehydes with chiral amidoxime led to unprecedented enantiopure 3-methylisoxazolidine-5-aryl-1,2,4-oxadiazoles. The menthone chiral auxiliary was then removed with acid hydrolysis. The new compounds were also screened for their in vitro antioxidant activity using DPPH and FRAP assays. Some of the compounds showed promising antioxidant activity.     

DNA cleavage,cytotoxic and antioxidant properties of Cistus laurifolius L. extracts

In this study, extracts of the root, branch and leaf parts of Cistus laurifolius L. were prepared using hexane, methylene chloride and ethanol solvents. DNA cleavage, cytotoxic and antioxidant properties of the prepared extracts were then investigated. The cytotoxic properties of the extracts were investigated in A549, DU-145, PNT-1A, MDA-MB231, CRL-4010 and HCT-116 cell lines. Among all prepared extracts, T4 (seed–methylene chloride) extract showed cytotoxic effects on more cancer cell lines compared to other extracts. Antioxidant tests were performed by DPPH (2,2-diphenyl-1-picrylhydrazil) radical scavenging and Folin-Ciocalteu methods. In both tests, it was determined that T7 (seed–ethanol) extract has a very strong antioxidant effect (IC₅₀ = 0,000015 μg/ml for the DPPH method). In DNA cleavage studies, the results obtained confirm the protection of DNA from hydroxyl radical damage in the presence of methanolic plant extracts. Consequently, we determined that some of the Cistus laurifolius L. extracts have significant biological properties on the studied cell lines.     

Automatic sequential determination of the hydrogen peroxide scavenging activity and evaluation of the antioxidant potential by the 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation assay in wines by sequential injection analysis

An automatic system that performs two analytical procedures, allowing the evaluation of the relative antioxidant capacity of wine samples, was developed. Automation was carried out using a sequential injection analysis (SIA) system that allowed, thanks to its versatility, the development of two methodologies. One is based on the decolorization assay of the 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical, using a spectrophotometric detector. A second methodology allowed the evaluation of the hydrogen peroxide scavenging activity by measuring the oxidation of homovanylic acid (HVA) to its fluorescent dimer, using a fluorescent detector.The developed automatic methodologies were evaluated using trolox as standard and subsequently using other antioxidant substances as gallic acid, caffeic acid, ascorbic acid, catechin and taxifolin which are abundant in wine and whose antioxidant activities were compared to that shown by trolox. The spectrophotometric and fluorimetric assays showed linearity intervals between 0.001 and 0.01 mM, and 0.001 and 0.008 mM of trolox, respectively.The evaluation of the antioxidant power of 20 white and red wine samples, from different Portuguese wine producing regions, was carried out sequentially, in the automatic system. The results were expressed in trolox equivalent antioxidant capacity (TEAC) and presented, for the ABTS and hydrogen peroxide scavenging activity methodologies, detection limits of 8.4 × 10⁻⁷ and 1.4 × 10⁻⁴ mM and relative standard deviation (R.S.D. (%)) in the range 0.6-2.4 and 1-1.8, respectively.     

Chemical constituents,Antibacterial and Acetylcholine esterase inhibitory activity of Cupressus macrocarpa leaves

Abstract

The chemical constituents of Cupressus macrocarpa were investigated. A new neolignan glycoside (1) in addition to nine known compounds were isolated. The acetylcholinesterase (AChE) inhibitory activity and antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) of different fractions and isolates of C. macrocarpa were evaluated. The light petroleum fraction showed the highest activity in both assays with IC₅₀ value of 88.79 µg/ml and 152.58 µg/ml for the AChE inhibitory activity and MRSA antibacterial activities, respectively. Weak to moderate activity were detected for the isolated compounds.     

Antibacterial,antioxidant and photocatalytic activity of novel Rubus ellipticus leaf mediated silver nanoparticles

Nanotechnology is an emerging field of science that has significant applications in applied sciences. In this study, silver nanoparticles (SNPs) were synthesized utilizing the leaf filtrate of Rubus ellipticus. SNPs were characterized using UV–visible spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction patterns to determine their morphology and chemical composition. The surface plasmon resonance of SNPs revealed a peak at 415 nm. The synthesized SNPs were mainly spherical crystals with an average size of 21.43 nm. When compared to plant extract and positive controls (AgNO₃ and penicillin), SNPs demonstrated significant bactericidal activity against all the tested bacteria (gram-positive and gram-negative). The most effective bactericidal activity was found against Pseudomonas aeruginosa, with a minimum inhibitory concentration of 1.25 µg/mL. In addition, a dose-dependent antioxidant activity of SNPs was found against the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical with an average IC50 value of 72.84 µg/mL. The photocatalytic activity of Methylene blue (MB) dye decomposition under sunlight was studied. The results showed that MB degraded by 98 % after 150 min in the sun. Overall, the findings of this study indicate that R. ellipticus biosynthesized SNPs may have bactericidal and photocatalytic effects.     

Comparative analysis of phytochemical profile,antioxidant and anti-inflammatory activity from Hibiscus manihot L. flower

Hibiscus manihot L. is a kind of healthy plant with edible value and health benefits, which possesses multiple pharmacological activities that are closely related to antioxidant and anti-inflammatory activities. The dynamic changes of main active components and biological activities in Hibiscus manihot L. flower (HMLF) during its flowering period were systematically studied to determine the appropriate harvest time. Chemopreventive efficacies of the investigated HMLF extracts, by means of their anti-inflammatory and antioxidant activities, were assessed. The sample harvested on early August had the supreme total flavonoid content, total phenolic content and the strongest antioxidant activity (DPPH radical scavenging activity (IC₅₀ 0.160 mg/mL), ABTS radical scavenging activity (1.570 mmol/g Trolox), reducing power (IC₅₀ 0.101 mg/mL) and FRAP (3.644 mmol FeSO₄/g)). The results of principal component analysis indicated that the primary active components included hyperin, isoquercetin, hibifolin and quercetin-3′-O-glucoside, which were strongly associated with the antioxidant activity in the early August sample, while neochlorogenic acid, chlorogenic acid and caffeic acid were associated with the anti-inflammatory activity. The extracts significantly inhibited lipopolysaccharide-induced nitric oxide production in RAW264.7 cells, especially the samples harvested around August, which was only 3.569 μΜ with the inhibition ratio of>50%. This study indicated that HMLF harvested on the early August possessed the highest antioxidant and anti-inflammatory potential and could be used as high bioactive resources for healthy production.     

Biosynthesis of Bixa orellana seed extract mediated silver nanoparticles with moderate antioxidant,antibacterial and antiproliferative activity

Biosynthesis of metallic silver nanoparticles (AgNPs) has gained much interest and offers an attractive alternate to physical and chemical approaches. In recent year several safe, easy, cost-effective, reproducible, and environmentally friendly synthesis approaches for silver nanoparticles have been developed. In this research work, a simple, cheap, and unexplored method was applied on green synthesis of AgNPs using secondary metabolites extracted from Bixa orellana seeds. The seeds are rich of flavonoids and phenolic compounds which presumably responsible for the fast reduction and stabilization of silver ion into silver nanoparticles. The biosynthesis process is very likely to be able to reduce silver ions under simple physiological conditions. The surface plasmon resonance (SPR) that was appeared at 420 nm in UV–vis spectrum, had confirmed the formation of AgNPs. Moreover, the functional groups in secondary metabolite that act as reducing, capping and stabilizing agents for silver nanoparticles, are identified by Fourier transform infrared (FTIR) spectra. An X-ray diffraction analysis generated four peaks for Bixa orellana seed extract mediated AgNPs positioned at 2θ angles of 38.1°, 44.2°, 64.6°, and 77.5° corresponding to crystal planes (1 1 1), (2 0 0), (2 2 0), and (3 1 1). Field emission scanning electron microscope (FESEM) and transmission electron microscopy (TEM) images confirmed the formation of nanosized silver particles. The z-average of the synthesized particles measured by dynamic light scattering (DLS) was found to be 92.9 nm. AgNPs synthesized exhibited remarkable antioxidant activity, antibacterial and antiproliferative activity against human breast (MCF-7) cell line. On the basis of our results, we conclude that biologically synthesized AgNPs exhibited favorable characteristics and have the potential to be used in biomedical fields.