Photophysical and Antibacterial Properties of Porphyrins Encapsulated inside Acetylated Lignin Nanoparticles.

Lignin has recently attracted the attention of the scientific community, as a suitable raw material for biomedical applications. In this work, acetylated lignin was used to encapsulate five different porphyrins, aiming to preserve their photophysical properties, and for further use as antibacterial treatment. The obtained nanoparticles were physically characterized, through dynamic light scattering size measurement, polydispersity index and zeta potential values. Additionally, the photophysical properties of the nanoparticles, namely UV-vis absorption, fluorescence emission, singlet oxygen production and photobleaching, were compared with those of the free porphyrins. It was found that all the porphyrins were susceptible to encapsulation, with an observed decrease in their fluorescence quantum yield and singlet oxygen production. These nanoparticles were able to exert an effective photodynamic bactericide effect (blue-LED light, 450-460 nm, 15 J/cm2) on Staphylococcus aureus and Escherichia coli. Furthermore, it was achieved a photodynamic bactericidal activity on an encapsulated lipophillic porphyrin, where the free porphyrin failed to diminish the bacterial survival. In this work it was demonstrated that acetylated lignin encapsulation works as a universal, cheap and green material for the delivery of porphyrins, while preserving their photophysical properties.

Chemical composition and biological potential of Thymus Willdenowii Boiss. & Reut. essential oil.

The fresh aerial parts of Thymus willdenowii Boiss. & Reut. (syn. Thymus hirtus Willd.) were hydrodistilled in a Clevenger type apparatus and analyzed by GC and GC-MS. 44 Components were identified representing 97.3%, with 1,8-cineole (34.62%), camphor (18.55%), α-pinene (9.46%) and camphene (5.38%) as the main components. T. willdenowii essential oil was not cytotoxic (CC50 = 97.65 µg/mL) towards Vero non-tumoural cells, exhibiting good antibacterial and antiproliferative (30.8 ± 3.1% inhibition) potentials against four tested pathogenic bacteria and Human colorectal cell line HT-29, respectively. The essential oil did not show a DPPH radical scavenging activity, by Electron Spin Resonance spectroscopy (ESR), and it lacks antiviral effect towards coxsackievirus B3.

Porphyrin-Loaded Lignin Nanoparticles Against Bacteria: A Photodynamic Antimicrobial Chemotherapy Application.

The need for alternative strategies to fight bacteria is evident from the emergence of antimicrobial resistance. To that respect, photodynamic antimicrobial chemotherapy steadily rises in bacterial eradication by using light, a photosensitizer and oxygen, which generates reactive oxygen species that may kill bacteria. Herein, we report the encapsulation of 5,10,15,20-tetrakis(4-hydroxyphenyl)-21H,23H-porphyrin into acetylated lignin water-dispersible nanoparticles (THPP@AcLi), with characterization of those systems by standard spectroscopic and microscopic techniques. We observed that THPP@AcLi retained porphyrin's photophysical/photochemical properties, including singlet oxygen generation and fluorescence. Besides, the nanoparticles demonstrated enhanced stability on storage and light bleaching. THPP@AcLi were evaluated as photosensitizers against two Gram-negative bacteria, Escherichia coli and Pseudomonas aeruginosa, and against three Gram-positive bacteria, Staphylococcus aureus, Staphylococcus epidermidis, and Enterococcus faecalis. THPP@AcLi were able to diminish Gram-positive bacterial survival to 0.1% when exposed to low white LED light doses (4.16 J/cm2), requiring concentrations below 5 µM. Nevertheless, the obtained nanoparticles were unable to diminish the survival of Gram-negative bacteria. Through transmission electron microscopy observations, we could demonstrate that nanoparticles did not penetrate inside the bacterial cell, exerting their destructive effect on the bacterial wall; also, a high affinity between acetylated lignin nanoparticles and bacteria was observed, leading to bacterial flocculation. Altogether, these findings allow to establish a photodynamic antimicrobial chemotherapy alternative that can be used effectively against Gram-positive topic infections using the widely available natural polymeric lignin as a drug carrier. Further research, aimed to inhibit the growth and survival of Gram-negative bacteria, is likely to enhance the wideness of acetylated lignin nanoparticle applications.

Antioxidant Flavonoids from Asteriscus maritimus.

One new flavonol glycoside, patuletin-7-Ο-[6-Ο-caffeoyl-2-Ο-[(S)-3-hydroxyisobutanoyl]glucopyranoside] (astermaritimoside) (1) and four known flavonoids, patuletin-7-Ο-ß-[-6-Ο-[(S)-3-hydroxyisobutanoyl]glucopyranoside] (2), patuletin-7-Ο-[6-Ο-caffeoylglucopyranoside] (3), patuletin-7-Ο-ß-D- glucopyranoside (4) and quercetin-3-Ο-ß-rutinoside (5) have been isolated from Asteriscus maritinus (L.) Less. Chemical structures were elucidated by mass spectrometric, and ¹H NMR, ¹³C NMR, COSY, HMQC and HMBC spectroscopic techniques. The antioxidative effect was evaluated using an electronic spin resonance (ESR) method in order to visualize the inhibition of the DPPH radical. The n-butanol fraction was found to possess a remarkable antioxidant activity that was correlated with the total amount of phenolics. The isolated compounds exhibited good antioxidant activity.

Lipocarbazole, an efficient lipid peroxidation inhibitor anchored in the membrane.

Lipid peroxidation is a major deleterious effect caused by oxidative stress. It is involved in various diseases such as atherosclerosis, rheumatoid arthritis and neurodegenerative diseases. In order to inhibit lipid peroxidation, antioxidants must efficiently scavenge free radicals and penetrate inside biological membranes. Lipocarbazole has recently been shown to be a powerful antioxidant in solution. Here, we show its powerful capacity as lipid peroxidation inhibitor. Its mechanism of action is rationalized based on molecular dynamics simulations on a biomembrane model, quantum calculations and experimental evaluation. The role of the lipocarbazole side chain is particularly highlighted as a critical chemical feature responsible for its antioxidant activity.

Partial structural characterization and antioxidant activity of a phenolic-xylan from Castanea sativa hardwood.

4-O-Methylglucuronoxylans (MGX) were isolated from chestnut wood sawdust using two different procedures: chlorite delignification followed by the classical alkaline extraction step, and an unusual green chemistry process of delignification using phthalocyanine/H2O2 followed by a simple extraction with hot water. Antioxidant properties of both MGX were evaluated against the stable radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) by electronic spin resonance (ESR). IC50 of water-extracted MGX was found to be less than 225 µg mL(-1), in contrast with alkali-extracted MGX for which no radical scavenging was observed. Characterization of extracts by colorimetric assay, GC, LC-MS and NMR spectroscopy provided some clues to understanding structure-function relationships of MGX in connection with their antioxidant activity.

Eight flavonoids and their potential as inhibitors of human cytomegalovirus replication.

The drugs currently available for treatment of severe human cytomegalovirus (HCMV) infections suffer from many drawbacks, particularly toxicity, and potential teratogenicity contraindicating their use in target populations such as pregnant women. The emergence of drug-resistant strains is still a problem for disease management, particularly in immunosuppressed populations where antivirals are used for extended periods of time. The flavonoid family of drugs contains promising candidates as they have low toxicity and inhibit different targets to currently available antivirals. We report here that, unlike their chalcon homologs, four flavonoids (baicalein, quercetin, quercetagetin and naringenin) inhibit various stages of HCMV replication, the most active anti-HCMV compound being baicalein and the less active and less selective being quercetagetin. These drugs could provide potential inhibitors of virus replication alone or in combination, without increased toxicity.

Blue light is phototoxic for B16F10 murine melanoma and bovine endothelial cell lines by direct cytocidal effect.

UNLABELLED: The large number of studies devoted to the effect of ultraviolet light on biological systems, contrasts with the lack of experimental data concerning the direct effects of visible light. It has been shown that blue light inhibited the growth of B16F10 melanoma cell lines and reduced the percentage of S phase cells. Yet these effects are poorly understood. MATERIALS AND METHODS: Two cell lines and irradiation with blue light were used. Cell mortality and a possible mechanism of action were investigated. RESULTS: Exposure of B16F10 melanoma and bovine endothelial cells to blue light (wavelength 450 nm, 10 J/cm(2) from a Waldman lamp) induced a rapid and large reduction in viability followed by the death of virtually all the irradiated cells within 24 h. These results led us to expose a patient with haemorrhagic cutaneous melanoma metastasis to blue light. Irradiation led to an immediate arrest of haemorrhage, an inhibition of tumour growth and extensive tumour necrosis 24h after irradiation. CONCLUSION: Exposure to blue light may offer new approaches to the treatment of superficial skin carcinomas in humans.

Radiolytic transformation of 2,2',4'-trihydroxychalcone.

Radiolysis of 2,2',4'-trihydroxychalcone, a natural antioxidant present in fruit and vegetables, was performed in ethanol in the absence or in the presence of dioxygen. The degradation process of chalcone was followed in de-aerated solution by HPLC, NMR, FAB-LSIMS mass spectroscopy and analytical TLC. Under anaerobic conditions, six new products (three couples of diastereoisomers) were identified. Four of them kept the chalcone skeleton with OCH(2)CH(3), CH(OH)CH(3) and H substitutions on C(alpha) and C(beta). Thus the target was the alpha-beta double bond on which ethanol radicals were added. The two other compounds were formed in a second stage and exhibited a cyclization between the substituent on C(beta) and the carbonyl group. In the presence of dioxygen, these reactions were prevented and chalcone was protected. This study was the first step toward understanding of the behavior chalcone in irradiated fruits and vegetables.

Castanea sativa Mill. leaves as new sources of natural antioxidant: an electronic spin resonance study.

The antioxidant potential of Castanea sativa Mill. leaf (sweet chestnut) was explored as a new source of active extracts. The capacity of the different fractions issued from aqueous, methanol, and ethyl acetate extracts to inhibit the stable free radical 2,2-diphenyl-1-pycryl-hydrazyl, superoxide anion, and hydroxyl radical was measured by electronic spin resonance. Their scavenging potential was analyzed versus their amount of phenolic compounds. Among the active fractions, the most effective one was A6, an ethyl acetate fraction, which contained a high level of total phenolic compounds (29.1 g/100 g). Thus, a different extraction procedure was performed to concentrate the active compounds of A6 in the new C. sativa leaf extract (CSLE). Compared to reference antioxidants (quercetin and vitamin E) and standard extracts (Pycnogenol, from French Pinus maritima bark, and grape marc extract), it was observed that A6 and CSLE have high antioxidant potentials, equivalent to at least those of reference compounds.

Radiolysis of kaempferol in water/methanol mixtures. Evaluation of antioxidant activity of kaempferol and products formed.

Oxidative reaction between hydroxymethyl radical ((*)CH(2)OH) and kaempferol, in methanol and methanol/water mixtures, was studied by gamma-radiolysis using a (60)Co source. Radiolysis was performed with concentrations and doses ranging from 5 x 10(-)(5) M to 5 x 10(-)(3) M and from 0.5 kGy to 14 kGy, respectively. Kaempferol degradation was followed by HPLC. Results showed that (*)CH(2)OH reacts with kaempferol at the 3-OH group and produces two depsides (K1 and K2) and other products including K3. K1, K2, and K3 were identified by NMR, LC-MS, and HRMS. The kaempferol degradation pathway leading to the K1, K2, and K3 formation is proposed. It was observed that the more water concentration in the irradiation medium increases, the more K2 concentration increases. Comprehension of food preservation is not clear because many phenomena occurring during irradiation are not established. Radiolysis of kaempferol in water/methanol mixtures helps to elucidate the phenomenon and it is possible that during the treatment of nutriments by gamma-irradiation, a series of products such as depside K2 could be formed. Antioxidant properties of kaempferol radiolysis products were evaluated according to their capacity to decrease the EPR DPPH (1,1-diphenyl-2-picrylhydrazil) signal and to inhibit superoxide radicals formed by the enzyme reaction "xanthine + xanthine oxidase".

Radiolysis of quercetin in methanol solution: observation of depside formation.

Radiolysis of the flavonol quercetin, a natural antioxidant, was performed in methanol. The degradation process was followed by HPLC analyses. The major product was identified as a depside (Q1) by NMR and LC-MS. The G(Q1) radiolytic factor was plotted versus the initial concentration of quercetin. This radiolytic process was attributed to the CH3O* radicals presented in the irradiated medium. The proposed mechanism invoked a stereospecific oxidation of the 3-hydroxyl group of quercetin which led to C-ring opening and to the formation of the depside Q1. In presence of water, Q1 was transformed into another depside, Q2, by an inverse esterification reaction. A chemical equilibrium was observed between Q1 and Q2. The comprehension of the radiolytic process of quercetin in methanol solution is of importance. Indeed, the same type of oxidative reactions could occur on flavonoids during preservation of food by ionizing radiation.