Antibacterial E ect of Chitosan–Gold Nanoparticles and Computational Modeling of the Interaction between Chitosan and a Lipid Bilayer Model

Pathogenic bacteria have the ability to develop antibiotic resistance mechanisms. Their action consists mainly in the production of bacterial enzymes that inactivate antibiotics or the appearance of modifications that prevent the arrival of the drug at the target point or the alteration of the target point itself, becoming a growing problem for health systems. Chitosan–gold nanoparticles (Cs-AuNPs) have been shown as effective bactericidal materials avoiding damage to human cells. In this work, Cs-AuNPs were synthesized using chitosan as the reducing agent, and a systematic analysis of the influence of the synthesis parameters on the size and zeta potential of the Cs-AuNPs and their UV-vis spectra was carried out. We used a simulation model to characterize the interaction of chitosan with bacterial membranes, using a symmetric charged bilayer and two different chitosan models with different degrees of the chitosan amine protonation as a function of pH, with the aim to elucidate the antibacterial mechanism involving the cell wall disruption. The Cs-AuNP antibacterial activity was evaluated to check the simulation model

Free radical scavengers and antioxidants from Baccharis grisebachii

Schmeda-Hirschmann, G, (reprint author) and Tapia A. Laboratorio de Química de Productos Naturales, Instituto de Química de Recursos Naturales, Universidad de Talca, Casilla 747, Talca, Chile.Rodriguez, J. and Theoduloz, C. Departamento de Ciencias Básicas Biomédicas, Facultad de Ciencias de la Salud, Universidad de Talca, Casilla 747, Talca, Chile.The exudate and seriated extracts from the aerial parts of Baccharis grisebachii (Asteraceae) which is recommended as a digestive and to relieve gastric ulcers in Argentina, showed activity as free radical scavengers and inhibited lipoperoxidation in erythrocytes. Assay-guided isolation led to seven p-coumaric acid derivatives and six flavonoids as the main active constituents of the crude drug. The activity towards the superoxide anion was mainly due to the flavonoid constituents. 5,7,4'-Trihydroxy-6-methoxyflavone and quercetin presented high activity (64 and 79%) even at 12.5 mug/ml. The xanthine oxidase inhibitory effect of the extracts can be related with the p-coumaric acid derivatives drupanin, 4-acetyl-3,5-diprenylcinnamic acid and trans-ferulic acid O-hexan-3-onyl-ether which showed IC50 values in the range 28-40 mug/ml. Both p-coumaric acid derivatives and flavonoids inhibited lipoperoxidation in erythrocytes. The highest activity was found for the p-coumaric acid derivatives 4-acetyl-3-prenyl-ethoxycinnamate, 3-prenyl-4-(4'-hydroxydihydrocinnamoyloxy)-cinnamate and trans-ferulic acid O-hexan-3-onyI-ether (69-82%) and the flavonoids 5,7,4'-trihydroxy-6-methoxyflavone, quercetin, 5,7,4'-trihydroxy-6,3'-dimethoxyflavone and 5,7,4'-trihydroxy-6,8-dimethoxyflavone (64-84%) at 100 mug/ml

Free radical scavengers, anti-inflammatory and analgesic activity of Acaena magellanica

Schmeda-Hirschmann, G.Laboratorio de Química de Productos Naturales, Instituto de Química de Recursos Naturales, Universidad de Talca, Casilla 747, Talca, Chile.Extracts of the whole plant Acaena magellanica (Rosaceae) were assessed for anti-inflammatory, antipyretic and analgesic activity in animal models. At 600 mg kg-1, the global ethanolic extract (GEE), dichloromethane (DCM) and defatted methanol (MeOH) fractions showed a mild anti-inflammatory effect in the carrageenan-induced guinea-pig paw oedema. The GEE, DCM and defatted MeOH fractions significantly reduced inflammation by 43.2, 40.5 and 42.1%, respectively. The GEE did not showed any significant antipyretic activity in doses up to 600 mg kg-1. A 20% w/v infusion administered orally at 16 mL kg-1 presented analgesic effect in the acetic acid-induced abdominal constriction test in mice. The GEE and MeOH extract of A. magellanica showed free radical scavenging activity in the diphenylpicrylhydrazyl decolouration assay. Assay-guided isolation led to quercetin, Q-3-O--D-glucoside, Q-3-O--D-galactoside, ellagic acid and catechin as the free radical scavengers. The saponins tormentic acid 28-O--D-galactopyranoside and 28-O--D-glucopyranoside were isolated from the polar extract. The structures were determined by spectroscopic methods

Biologically active alkaloids and a free radical scavenger from Prosopis species

Luis Astudillo, Cristina Theoduloz and Guillermo Schmeda-Hirschmann. Laboratorio de Química de Productos Naturales, Instituto de Química de Recursos Naturales, Universidad de Talca, Casilla 747, Talca, Chile.Abstract The biological activity of extracts from the aerial parts of five Argentinian Prosopis species and the exudate of P. flexuosa were assessed for DNA binding, β-glucosidase inhibition and free radical scavenging effect using the DPPH decoloration assay. DNA binding effect was found mainly in the basic fraction. The alkaloids tryptamine as well as piperidine and phenethylamine derivatives were isolated from the basic extracts. At 0.50 mg/ml, DNA binding activities ranged from 28% for tryptamine to 0–27% for the phenethylamine and 47–54% for the piperidine derivatives. Tryptamine and 2-β-methyl-3-β-hydroxy-6-β-piperidinedodecanol showed a moderate inhibition (27–32%) of the enzyme β-glucosidase at 100 μg/ml. The exudate of P. flexuosa displayed a strong free radical scavenger effect in the DPPH decoloration assay. The main active constituent was identified as catechin

Free Radical Scavengers and Antioxidants from Tagetes mendocina

Schmeda-Hirschmann, G. ; Tapia, A. Universidad de Talca, Instituto de Quımica de Recursos Naturales, Laboratorio de Productos Naturales, Casilla 747, Talca, Chile. Theoduloz, C. ;Rodriguez, J. Universidad de Talca, Departamento de Ciencias Basicas Biome dicas, Facultad de Ciencias de la Salud, Casilla 747, Talca, Chile.Tagetes mendocina (Asteraceae) is a medicinal plant widely used in the Andean provinces of Argentina. Preliminary assays showed free radical scavenging activity in the methanol extract of the aerial parts, measured by the decoloration of a methanolic solution of the 1,1- diphenyl-2-picrylhydrazyl radical (DPPH) and scavenging of the superoxide anion. Assayguided isolation led to 4 -hydroxyacetophenone (1), protocatechuic acid (2), syringic acid (3), patuletin (4), quercetagetin 7-O- -d-glucoside (5), patuletin 7-O- -d-glucoside (6) and axillarin 7-O- -d-glucoside (7) as the free radical scavengers and antioxidant compounds from Tagetes mendocina. On the basis of dry startingmaterial, the total phenolic content of the crude drugwas 3.00% with 0.372% of flavonoids. The content of compounds 1Ð7 in the crude drugwas 0.008, 0.015, 0.010, 0.029, 0.238, 0.058 and 0.017%, respectively. Quercetagetin 7-O- -d-glucoside proved to be the main free radical scavenger of the extracts measured by the DPPH decoloration test as well as for quenchingthe superoxide anion and inhibition of lipoperoxidation in erythrocytes. In the lipid peroxidation assay the percentual inhibition was related with the number of methoxy groups in the molecule, ranging from 86% for the quercetagetin glucoside to 67% for the monomethoxylated and 31% for the dimethoxylated derivative. The compounds showed low cytotoxicity towards human lungfibroblasts with IC50 > 1mm for compounds 1Ð3 and 0.24 to 0.52 mm for the flavonoids 4Ð7

Free-radical Scavengers and Antioxidants from Peumus boldus Mol. (

G. Schmeda-Hirschmann; L. Astudillo. Laboratorio de Qui­mica de Productos Naturales, Instituto de Qui­mica de Recursos Naturales, Universidad de Talca, Casilla 747, Talca, Chile; J. A. Rodriguez;C. Theoduloz. Departamento de Ciencias Biomedicas, Facultad de Ciencias de la Salud, Universidad de Talca, Casilla 747, Talca, Chile.The dry leaves of Peumus boldus (Monimiaceae) are used in infusion or decoction as a digestive and to improve hepatic complains. Preliminary assays showed free-radical scavenging activity in hot water extracts of boldo leaves, measured by the decoloration of a methanolic solution of the 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH). Assay-guided isolation led to the active compounds. Catechin proved to be the main free-radical scavenger of the extracts. Lipid peroxidation in erythrocytes was inhibited by boldo extracts and fractions at 500μg/ml with higher effect for the ethyl acetate soluble and alkaloid fractions. The IC[sub50] for catechin and boldine in the lipid peroxidation test were 75.6 and 12.5 μg/ml, respectively. On the basis of dry starting material, the catechin content in the crude drug was 2.25% while the total alkaloid calculated as boldine was 0.06%. The activity of boldine was six times higher than catechin in the lipid peroxidation assay. However, the mean catechin:total alkaloid content ratio was 37:1. The relative concentration of alkaloids and phenolics in boldo leaves and their activity suggest that free-radical scavenging effect is mainly due to catechin and flavonoids and that antioxidant effect is mainly related with the catechin content. The high catechin content of boldo leaves and its bioactivity suggest that quality control of Boldo folium has to combine the analysis of catechin as well as their characteristic aporphine alkaloids

Constituents of the Argentinian medicinal plant Baccharis grisebachii and their antimicrobial activity

Schmeda-Hirschmann,G. Laboratorio de Química de Productos Naturales, Instituto de Química de Recursos Naturales, Universidad de Talca, Casilla 747, Talca, Chile.The resinous exudate of Baccharis grisebachii which is used to treat ulcers, burns, and skin sores in Argentina showed activity towards dermatophytes and bacteria. Two diterpenes, eight p-coumaric acid derivatives, and two flavones were isolated from the exudate and the structures elucidated by spectroscopic methods. 3-Prenyl-p-coumaric acid and 3,5-diprenyl-p-coumaric acid were active towards Epidermophyton floccosum and Trichophyton rubrum with MICs of 50 and 100–125 μg/ml, respectively. The diterpene labda-7,13E-dien-2β,15-diol was active towards Epidermophyton floccosum and Trichophyton rubrum with MICs of 12.5 μg/ml while the MIC against Microsporum canis and Trichophyton mentagrophytes was 25 μg/ml. The diterpene was also active towards Microsporum gypseum with a MIC of 50 μg/ml, and showed inhibition in both Staphylococcus aureus (methicilline resistant and sensible strains) with MICs of 125 μg/ml. The results support the use of Baccharis grisebachii in Argentinian traditional medicine

1 beta,7 beta-Dihydroxydehydroabietic acid, a new biotransformation product of dehydroabietic acid by Aspergillus

Schmeda-Hirschmann, G. Instituto de Química de Recursos Naturales, Universidad de Talca, Casilla Talca, 747, Chile