Synthesis of silver nanoparticles using Ziziphus nummularia leaf extract and evaluation of their antimicrobial, antioxidant, cytotoxic and genotoxic potential (4-in-1 system).

This study reports the synthesis of silver nanoparticles (AgNPs) from silver nitrate by leaf extract of a medicinal plant Ziziphus nummularia. The leaf extract acts as a reducing and stabilizing agent for the formation of nanoparticles. The green synthesized AgNPs were characterized by ultraviolet-visible (UV-vis) spectroscopy, Fourier transform infrared (FITR) spectroscopy, Thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM) analysis and evaluated their antimicrobial, antioxidant, cytotoxic and genotoxic potential. The UV-Vis spectroscopy showed a characteristic absorption peak at 430 nm due to surface plasma resonance. TEM analysis showed that synthesized AgNPs were spherical and oval with an average size of 25.96 nm. AgNPs showed effective antimicrobial activity (lowest MIC-0.625 µg/mL against Escherichia coli), synergistic antimicrobial activity (lowest ΣFIC 0.09 with chlormaphenicol against Corynebacterium rubrum) and antibiofilm activity. AgNPs showed strong DPPH activity with IC50 - 520 µg/mL and ABTS activity IC50 - 55 µg/mL and reducing capacity assessment. In vitro cytotoxic effect was evaluated by MTT assay against HeLa cells, breast cells and fibroblast cells. Genotoxic effect was evaluated by comet assay. AgNPs displayed dose-dependent cytotoxic and genotoxic effect. Our findings indicated that synthesized AgNPs could be considered as multifunctional and have great potential for use in biomedical applications.HighlightsSilver nanoparticles were synthesized using leaf extract of Ziziphus nummulariaCharacterization was done by various spectral techniquesAntimicrobial efficacy was demonstrated against an array of bacteriaAgNPs exhibited significant cytotoxic effect against HeLa cell lineAgNPs showed cytotoxicity and genotoxicity in a dose-dependent manner.

Synthesis and characterization of silver nanoparticles using Caesalpinia pulcherrima flower extract and assessment of their in vitro antimicrobial, antioxidant, cytotoxic, and genotoxic activities.

Caesalpinia pulcherrima flower extract mediated synthesis of silver nanoparticles was attempted in the present work including optimization of some procedure parameters. Characterization of synthesized silver nanoparticles was done by various spectral analyses. The size of synthesized silver nanoparticles was 12 nm and they were spherical in shape. The green synthesized silver nanoparticles were further evaluated for antimicrobial, antioxidant, cytotoxic, and genotoxic activities; they showed good antimicrobial, antioxidant, and cytotoxic effects. Genotoxic study revealed non-toxic nature at lower concentration. Overall results suggest that the synthesized silver nanoparticles have pronounced applicability in pharmaceutical and biomedical field.

Evaluation of anti-herpetic and antioxidant activities, and cytotoxic and genotoxic effects of synthetic alkyl-esters of gallic acid.

The n-alkyl esters of gallic acid (CAS 13857-8) have a diverse range of uses as antioxidants in food, cosmetics and pharmaceutical industries. Pharmaceutical studies performed with these compounds have found that they have many therapeutic potentialities including anti-cancer, antiviral and antimicrobial properties. However, more interest has been devoted to their antioxidant activity due to the ability to scavenge and reduce reactive oxygen species (ROS) formation. In this study, gallic acid and 14 different alkyl gallates were tested. The cytotoxicity and anti-herpetic (HSV-1, KOS and 29-R strains) activity were studied by using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) colorimetric assay and the cell viability by using the Trypan blue dye exclusion method. The genotoxicity was studied by the Comet assay and the antioxidant activity by using the DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging and microsomal lipid peroxidation-inhibiting activities. The results showed that all the tested compounds have anti-herpetic activity at non cytotoxic concentrations with selectivity indices (SI = CC50/EC50) varying from 0.89 to 18.34, depending on the used HSV-1 strain. It was observed that all tested alkyl gallates showed some degree of genotoxicity, at the tested concentrations, except cetyl gallate, at 256.60 micromol/L (p <0.05, t-Student test), probably induced by ROS released by infected cells and/or by the alkyl gallates that were not antioxidants, at the tested concentrations, in which they demonstrated anti-herpetic activity. The hydroxyl groups can induce DNA damage due interactions with some metal ions, which are naturally present in the culture medium supplemented with fetal bovine serum, probably explaining the genotoxicity detected. However, the obtained results showed considerable antioxidant activity at smaller concentrations, when compared to quercetin which is considered as a reference drug due to its already described antioxidant potential: DPPH radical scavenging activity with IC50 values varying from 17 to 31 micromol/L; and microsomal lipid peroxidation-inhibiting activity with IC50 values varying from 21 to 59 micromol/L. It was observed that the presence of hydroxyl groups in these molecules is important for their pharmacological profile, but the length of the lateral carbonic chain does not have considerable influence.

Synthesis and antiviral evaluation of a mutagenic and non-hydrogen bonding ribonucleoside analogue: 1-beta-D-Ribofuranosyl-3-nitropyrrole.

Synthetic small molecules that promote viral mutagenesis represent a promising new class of antiviral therapeutics. Ribavirin is a broad-spectrum antiviral nucleoside whose antiviral mechanism against RNA viruses likely reflects the ability of this compound to introduce mutations into the viral genome. The mutagenicity of ribavirin results from the incorporation of ribavirin triphosphate opposite both cytidine and uridine in viral RNA. In an effort to identify compounds with mutagenicity greater than that of ribavirin, we synthesized 1-beta-D-ribofuranosyl-3-nitropyrrole (3-NPN) and the corresponding triphosphate (3-NPNTP). These compounds constitute RNA analogues of the known DNA nucleoside 1-(2'-deoxy-beta-D-ribofuranosyl)-3-nitropyrrole. The 3-nitropyrrole pseudobase has been shown to maintain the integrity of DNA duplexes when placed opposite any of the four nucleobases without requiring hydrogen bonding. X-ray crystallography revealed that 3-NPN is structurally similar to ribavirin, and both compounds are substrates for adenosine kinase, an enzyme critical for conversion to the corresponding triphosphate in cells. Whereas ribavirin exhibits antiviral activity against poliovirus in cell culture, 3-NPN lacks this activity. Evaluation of 3-NPNTP utilization by poliovirus RNA-dependent RNA polymerase (RdRP) revealed that 3-NPNTP was not accepted universally. Rather, incorporation was only observed opposite A and U in the template and at a rate 100-fold slower than the rate of incorporation of ribavirin triphosphate. This diminished rate of incorporation into viral RNA likely precludes 3-NPN from functioning as an antiviral agent. These results indicate that hydrogen bonding substituents are critical for efficient incorporation of ribonucleotides into RNA by viral RdRPs, thus providing important considerations for the design of improved mutagenic antiviral nucleosides.

Inhibitory effects of antioxidants on formation of heterocyclic amines.

It is important to search for effective antioxidants to suppress formation of mutagenic and carcinogenic heterocyclic amines (HCAs), like 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), because these HCAs are considered to be probable human carcinogens. The effects of various food-derived antioxidants on MeIQx formation were examined by their addition (0.2 mmol each) to mixtures of creatine (0.4 mmol), glycine (0.4 mmol) and glucose (0.2 mmol), and heating at 128 degreesC for 2 h. Glycine was replaced by l-phenylalanine in the case of PhIP formation. Among the 14 kinds of antioxidants tested, green tea catechins and the major component [(-)-epigallocatechin gallate], two flavonoids (luteolin and quercetin) and caffeic acid were found to clearly suppress the formation of both MeIQx and PhIP, being 3.2-75% of the level of the controls. These phenolic antioxidants also reduced the total mutagenicity of the heated mixtures. The results suggest that foodstuffs containing catechins, flavonoids and caffeic acid may suppress the formation of HCAs in cooked foods.

Synthetic routes to the food carcinogen 2 amino-3,8-dimethylimidazo[4,5-f]quinoxaline (8-MeIQx) and related compounds.

A review of five different routes to the synthesis of the grilled or fried food carcinogen 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (8-MeIQx) and of closely related compounds developed in different laboratories is presented. Interest in the synthesis of these amines began in the late 1970s when the research group led by Professor T. Sugimura (National Cancer Center, Tokyo) detected extremely high mutagenicity in the charred parts of fish and meat that could not be explained only by the presence of polyaromatic hydrocarbons. A number of new mutagenic heterocyclic amines have been detected, isolated and identified since then (de Meester, 1989; Overvik and Gustafsson, 1990; Felton and Knize, 1991; Jägerstad et al., 1991). It is still not entirely clear how these compounds are formed during cooking. For the "IQ-group" of the amines (2-amino-3-methylimidazo-quinoline and -quinoxaline congeners), a formation pathway from Maillard reaction products and creatinine was conceived by Professor K. Olsson (this laboratory) and presented at the 183rd meeting of the American Chemical Society, Las Vegas in 1982 (Jägerstad et al., 1983). However, the amounts of the amines formed during cooking or in model reaction systems are very small. Therefore, efficient and unambiguous synthetic methods yielding the compounds in isomerically pure form are required for reference purposes in analytical work and structure-biological activity studies. For instance, compare the mutagenicity of 4,8- and 5,8-DiMeIQx, and PhIP and its 3-methyl isomer shown on the following page. The pure compounds are also required in large quantities for long-term animal feeding studies. The length of this article does not allow a presentation of the published synthetic methods for all the heterocyclic amines. Therefore, the syntheses of only one of the food mutagens, 8-MeIQx, and some related compounds are presented. This will hopefully demonstrate the sort of problems the organic chemist encounters and some of their possible solutions. For a relatively recent reference list covering the synthesis, isolation, detection, formation and biological activity of these food mutagens and carcinogens the reader is referred to Hatch et al. (1988).

Enzymatic reduction of xenobiotic alpha,beta-unsaturated ketones: formation of allyl alcohol metabolites from shogaol and dehydroparadol.

A novel reductive metabolism of shogaol [1-(4'-hydroxy-3'-methoxyphenyl)-deca-4-ene-3-one], a major pungent and pharmacologically active principle of ginger, was investigated in rat liver in vitro. The ethyl acetate extractable metabolites formed by incubation of this alpha,beta-unsaturated ketone with rat liver 12,000 x g supernatant fortified with NADPH-generating system were analyzed by high performance chromatography and gas chromatography/mass spectrometry. In addition to the saturated ketone and reduced alcohol metabolites, an allyl alcohol, 1-(4'-hydroxy-3'-methoxyphenyl)-deca-4-ene-3-ol, was identified as a new metabolite of shogaol. Likewise, dehydroparadol [1-(4'-hydroxy-3'-methoxyphenyl)-deca-1-ene-3-one], a non-pungent analog of shogaol, was also reduced to the corresponding allyl alcohol by the postmitochondrial fraction of rat kidney in the presence of NADPH-generating system.

Isolation, synthesis, and antitumor evaluation of spirohydantoin aziridine, a mutagenic metabolite of spirohydantoin mustard.

Spirohydantoin mustard (SHM), a central nervous system directed nitrogen mustard with anticancer activity, was metabolized in the presence of mouse liver postmitochondrial supernatant (9000g fraction) to a nonpolar alkylating metabolite. The metabolite was isolated by thin-layer chromatography of chloroform or ethyl acetate extracts of incubation mixtures, and its structure was established by mass spectral analysis, synthesis, and cochromatography. The metabolite, spirohydantoin aziridine, was mutagenic for Salmonella typhimurium TA1535 in the Ames assay but inactive as an antitumor agent against P388 leukemia in vivo.