Coumarin-poly(2-oxazoline)s as synergetic and protein-undetected nanovectors for photodynamic therapy

Because of the difficult challenges of nanopharmaceutics, the development of a variety of nanovectors is still highly desired. Photodynamic therapy, which uses a photosensitizer to locally produce reactive oxygen species to kill the undesired cells, is a typical example for which encapsulation has been shown to be beneficial. The present work describes the use of coumarin-functionalized polymeric nanovectors based on the self-assembly of amphiphilic poly(2-oxazoline)s. Encapsulation of pheophorbide a, a known PDT photosensitizer, is shown to lead to an increased efficiency compared to the un-encapsulated version. Interestingly, the presence of coumarin both enhances the desired photocytotoxicity and enables the crosslinking of the vectors. Various nanovectors are examined, differing by their size, shape and hydrophilicity. Their behaviour in PDT protocols on HCT-116 cells monolayers is described, the influence of their crosslinking commented. Furthermore, the formation of a protein corona is assessed.

Development and validation of QuEChERS-based extraction for quantification of nine micropollutants in wastewater treatment plant

A modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was established for simultaneous quantification of eight pharmaceutical molecules (2-hydroxyibuprofen, diclofenac, ibuprofen, propranolol, ofloxacin, oxazepam, sulfamethoxazole, carbamazepine) and caffeine in environmental matrices. Analysis was performed by ultra-high-performance liquid chromatography with tandem mass spectrometry (UHPLC-MS-MS). Quantification was performed by using the ¹³C internal standard method for each molecule. Two methods were firstly optimized on freeze-dried waste activated sludge and then applied and validated on real complex matrices, which have contrasted physicochemical properties, i.e., clarified wastewater and primary sludge. The combination of acetate buffer with MgSO₄ (protocol A) and citrate buffer with Na₂SO₄ (protocol B) was found necessary to recover the nine targeted compounds. Adding a higher salts quantity of Na₂SO₄ (protocol B) compared to MgSO₄ (protocol A) is crucial to increase the ionic strength of the aqueous solution and to obtain comparable extraction recoveries of the targeted molecules. Adding two times solvent volume to the aqueous phase leads to increased absolute recovery for all molecules and both protocols. After demonstration of the final protocol's performance on the control matrix, its robustness was tested on the matrices of interest. As a result, the two proposed detection methods exhibit good reproducibility, high sensitivity, and high reliability.

Development and validation of liquid chromatography combined with tandem mass spectrometry methods for the quantitation of simalikalactone E in extracts of Quassia amara L. and in mouse blood

INTRODUCTION

Simalikalactone E (SkE) from Quassia amara, has been proved to be a valuable anti-malarial and anti-cancer compound. As SkE is very scarce, methods of quantitation are needed in order to optimise its isolation process and to determine pharmacokinetic data.

OBJECTIVE

To validate methods using liquid chromatography coupled to mass spectrometry for the quantitation of SkE in plant extracts and in biological fluids.

METHODS

High- and ultrahigh-performance liquid chromatography (UHPLC) coupled to ion trap mass spectrometry (MS) with single ion monitoring detection and to triple quadrupole-linear ion trap tandem mass spectrometry with multiple reaction monitoring detection methods were developed. Validation procedure was realised according to the International Conference on Harmonisation guideline. Methanol extracts of dried Quassia amara leaves, and mouse-blood samples obtained after various routes of administration, were analysed for SkE.

RESULTS

Methods were validated and gave similar results regarding the content of SkE expressed per kilogram of dry leaves in the traditional decoction (160 ± 12 mg/kg) and in the methanol extract (93 ± 2 mg/kg). The recovery of the analyte from mouse blood ranged from 80.7 to 119.8%. Simalikalactone E was only detected using UHPLC-MS/MS (0.2 ± 0.03 mg/L) in mouse blood after intravenous injection: none was detected following intraperitoneal or oral gavage administration of SkE.

CONCLUSION

The LC-MS methods were used for the quantitation of SkE in plant extracts and in mouse blood. These methods open the way for further protocol optimisation of SkE extraction and the determination of its pharmacokinetic data.

Tryptophan oxidation photosensitized by pterin

Pterins are normal components of cells and they have been previously identified as good photosensitizers under UV-A irradiation, inducing DNA damage and oxidation of nucleotides. In this work, we have investigated the ability of pterin (Ptr), the parent compound of oxidized pterins, to photosensitize the oxidation of another class of biomolecules, amino acids, using tryptophan (Trp) as a model compound. Irradiation of Ptr in the UV-A spectral range (350 nm) in aerated aqueous solutions containing Trp led to the consumption of the latter, whereas the Ptr concentration remained unchanged. Concomitantly, hydrogen peroxide (H₂O₂) was produced. Although Ptr is a singlet oxygen ((1)O₂) sensitizer, the degradation of Trp was inhibited in O₂-saturated solutions, indicating that a (1)O₂-mediated process (type II oxidation) was not an important pathway leading to Trp oxidation. By combining different analytical techniques, we could establish that a type I photooxidation was the prevailing mechanism, initiated by an electron transfer from the Trp molecule to the Ptr triplet excited state, yielding the corresponding radical ions (Trp(·+)/Trp(-H)· and Ptr(·-)). The Trp reaction products that could be identified by UPLC-mass spectrometry are in agreement with this conclusion.

Degradation of 2,4-dihydroxibenzoic acid by vacuum UV process in aqueous solution: kinetic, identification of intermediates and reaction pathway

2,4-Dihydroxybenzoic acid (2,4-DHBA) is found frequently as a pollutant in natural waters and represents a threat to water quality because it is a precursor to the formation of quinones which are highly toxic. The degradation of 2,4-DHBA using the vacuum UV photolysis of water has been investigated. Irradiation was carried out in an annular photoreactor equipped with a Xe-excimer lamp situated in the centre and emitting at 172 nm. The degradation kinetic followed a pseudo first order and the reaction has been found to be very heterogeneous, especially at low concentration. Impacts of oxygen or temperature have also been investigated but no effect has been shown. LC-MS and HPLC-UV combined with other analytical techniques allowed the identification of the formation of trihydroxybenzoïc acids and trihydroxybenzenes which underwent a ring opening, conducting to the formation of aliphatic products named α, β, δ and γ. These products were in turn degraded successively into maleïc acid, malic and succinic acid, malonic acid, glyoxalic acid and oxalic acid before reaching the complete mineralization in about 180 min. The proposed reaction pathway has shown to be very different from the one observed for the TiO(2) photocatalysis which involves only holes (h(+)) without any formation of aromatic intermediates. The different behaviours of 2,4-DHBA towards the h(+) and HO make it a good probe to identify involved entities.

Photochemistry of dihydrobiopterin in aqueous solution

Dihydrobiopterin (H(2)Bip) and its oxidized analogue, biopterin (Bip), accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder in which the protection against UV radiation fails. The photochemistry of H(2)Bip was studied in neutral aqueous solutions upon UV-A irradiation (320-400 nm) at room temperature. The photochemical reactions were followed by UV/vis spectrophotometry, HPLC and enzymatic methods for hydrogen peroxide (H(2)O(2)) determination. Photoproducts were analyzed by means of electrospray ionization mass spectrometry. Under anaerobic conditions, excitation of H(2)Bip leads to the formation of at least two isomeric dimers with molecular masses equal to exactly twice the molecular mass of the reactant. This reaction takes place from the singlet excited state of the reactant. To the best of our knowledge, this is the first time that the photodimerization of a dihydropterin is reported. In the presence of air, the dimers are again the main photoproducts at the beginning of the reaction, but a small proportion of the reactant is converted into Bip. As the reaction proceeds and enough Bip accumulates in the solution, a photosensitized process starts, where Bip photoinduces the oxidation of H(2)Bip to Bip, and H(2)O(2) is formed. As a consequence, the rates of H(2)Bip consumption and Bip formation increase as a function of irradiation time, resulting in an autocatalytic photochemical process. In this process, Bip in its triplet excited state reacts with the ground state of H(2)Bip. The mechanisms involved are analyzed and the biological implications of the results are discussed.

A glucuronidation pathway of capecitabine occurs in rats but not in mice and humans

Glucuronidation of 5'-DFCR, a metabolite of capecitabine, was confirmed in experimental models from rats whereas 5'-DFCR glucuronide was detected neither in bile or liver from mice nor in liver microsomes from human. Metabolic interactions at the level of the glucuronidation pathway between CAP and other drugs are unlikely in patients.

Comparison of flavonoid profiles of Agauria salicifolia (Ericaceae) by liquid chromatography-UV diode array detection-electrospray ionisation mass spectrometry

Liquid chromatography (LC) coupled to negative electrospray ionisation (ESI) tandem mass spectrometry (MS/MS) was used for the rapid and sensitive identification of flavonoid compounds in Agauria salicifolia. The leaf flavonoid content in individual of A. salicifolia originating from population with contrasted ecogeographical situation and morphological characteristics was found to be variable qualitatively and highly variable quantitatively. Identification of the compounds was carried out by interpretation of UV, MS and MS/MS spectra. Fourteen flavonoids were identified, all of which had not previously been reported in Agauria spp. Two flavonol-O-glucuronides were found to differentiate the two populations.

The antimalarial drug artemisinin alkylates heme in infected mice

Heme alkylation by the antimalarial drug artemisinin is reported in vivo, within infected mice that have been treated at pharmacologically relevant doses. Adducts resulting from the alkylation of heme by the drug were characterized in the spleen of treated mice, and their glucuroconjugated derivatives were present in the urine. Because these heme-artemisinin adducts were not observed in noninfected mice, this report confirms that the alkylating activity of this antimalarial drug is related to the presence of the parasite in infected animals. The identification of heme-artemisinin adducts in mice should be considered as the signature of the alkylation capacity of artemisinin in vivo.

The vasoactive peptide adrenomedullin is secreted by adipocytes and inhibits lipolysis through NO-mediated beta-adrenergic agonist oxidation

Adipocytes are known to secrete a number of adipokines, but many adipocyte secretions and their functional importance remain to be characterized. This work shows that human white adipocytes and 3T3-F442A-derived adipocytes produce adrenomedullin (AM) and that AM acts in an autocrine/paracrine way on lipid metabolism by extracellular inactivation of isoproterenol, a beta-adrenergic agonist. AM is described as a counter-regulatory factor involved in the control of cardiovascular homeostasis. This peptide is believed to protect the heart from several complications implicated in obesity-linked cardiomorbidity, such as arterial hypertension, cardiac fibrosis, and decreased sinusal variability. The exact source of circulating AM remains a matter of debate, although endothelial and vascular smooth muscle cells seem to be important sites of production. We show that human adipose cells and 3T3-F442A-derived adipocytes express AM receptors and secrete AM. The function of this feature was investigated in 3T3-F442A cell line at the level of lipolysis regulation. AM inhibited beta-adrenergic-stimulated lipolysis by a nitric oxide (NO)-dependent mechanism, inducing a significant decrease in pD2 value for isoproterenol (8.6 +/- 0.2 vs. 9.8 +/- 0.1, P<0.001). This effect is cGMP-independent since it occurred in the presence of the NO-sensitive guanylate cyclase inhibitor ODQ. It is apparently mediated by a novel extracellular mechanism. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) demonstrated that AM-produced NO oxidized isoproterenol to generate its aminochrome, namely isoprenochrome. Isoprenochrome amounts were increased 3.62 +/- 1.13-fold in cell culture media (P<0.05). We describe for the first time that AM down-regulates lipolysis in adipocytes through the chemical modification of a beta-agonist.

Alkylation of human hemoglobin A0by the antimalarial drug artemisinin

In vitro, the heme cofactor of human iron(II) hemoglobin was efficiently and quickly alkylated at meso positions by the peroxide-based antimalarial drug artemisinin, leading to heme-artemisinin-derived covalent adducts. This reaction occurred in the absence of any added protease or in the presence of an excess of an extra non-heme protein, or even when artemisinin was added to hemolysed human blood. This activation of artemisinin by the heme moiety of non-digested hemoglobin clearly indicates the high affinity of this drug for heme, and its efficient alkylating ability under very mild conditions.

Hb O-Tibesti [beta121(GH4)Glu-->Lys; beta11(A8)Val-->Ile], a hemoglobin variant carrying in the same beta chain the substitutions of Hb O-Arab and Hb Hamilton, found in combination with Hb S [beta6(A3)Glu-->Val]

Hb O-Tibesti, carries in the same chain the substitution of Hb O-Arab [beta121(GH4)Glu-->Lys] and that of Hb Hamilton [beta11(A8)Val-->Ile]. Hb O-Tibesti may be distinguished from Hb O-Arab by polyacrylamide gel electrophoresis in the presence of urea and Triton-X100, and by reversed phase high performance liquid chromatography. It was found in a compound heterozygous condition with Hb S [beta6(A3)Glu-->Val] in a child of Chad-Sudanese descent, suffering from a sickle cell syndrome. Compared to the classical description of the Hb S/Hb O-Arab association, the additional Hb Hamilton mutation does not seem to modify the clinical presentation.

Peroxynitrite-induced nitration of tyrosine-34 does not inhibit Escherichia coli iron superoxide dismutase

The peroxynitrite anion is a potent oxidizing agent, formed by the diffusion-limited combination of nitric oxide and superoxide, and its production under physiological conditions is associated with the pathologies of a number of inflammatory and neurodegenerative diseases. Nitration of Escherichia coli iron superoxide dismutase (Fe-SOD) by peroxynitrite was investigated, and demonstrated by spectral changes and electrospray mass spectroscopic analysis. HPLC and mass studies of the tryptic digests of the mono-nitrated Fe-SOD indicated that tyrosine-34 was the residue most susceptible to nitration by peroxynitrite. Exclusive nitration of this residue occurred when Fe-SOD was exposed to a cumulative dose of 0.4 mM peroxynitrite. Unlike with human Mn-SOD, this single modification did not inactivate E. coli Fe-SOD at pH 7.4. When Fe-SOD was exposed to higher concentrations of peroxynitrite (7 mM), eight tyrosine residues per subunit of the protein, of the nine available, were nitrated without loss of catalytic activity of the enzyme. The pK(a) of nitrated tyrosine-34 was determined to be 7.95+/-0.15, indicating that the peroxynitrite-modified enzyme appreciably maintains its protonation state under physiological conditions.

A fast and efficient metal-mediated oxidation of isoniazid and identification of isoniazid-NAD(H) adducts

It is currently believed that isoniazid (INH) is oxidised inside Mycobacterium tuberculosis to generate, by covalent attachment to the nicotinamide ring of NAD(H) (beta-nicotinamide adenine dinucleotide), a strong inhibitor of InhA, an enzyme essential for mycolic acid biosynthesis. This work was carried out to characterise the InhA inhibitors (named INH-NAD(H) adducts) which are generated, in the presence of the nicotinamide coenzyme NAD+, by oxidation of INH with manganese(III) pyrophosphate, a nonenzymatic and efficient oxidant used to mimic INH activation by the catalase-peroxidase KatG inside M. tuberculosis. The oxidation process is almost complete in less than 15 minutes (in comparison to the slow activation obtained in the KatG-dependent process (2.5 hours) or in the nonenzymatic O2/Mn(II)-dependent activation (5 hours)). The alkylation of NAD+ by the postulated isonicotinoyl radical generates, in solution, a family of INH-NAD(H) adducts. Analyses with liquid chromatography/electrospray ionisation mass spectrometry (LC/ESI-MS) and experiments performed with 18O- and 2H-labelled substrates allowed us to propose two open and four hemiamidal cyclised dihydropyridine structures as the main forms present in solution; these result from the combination of the isonicotinoyl radical and the nicotinamide part of NAD+. A small amount of a secondary oxidation product was also detected. Structural data on the forms present in solution should help in the design of inhibitors of enzymes involved in the biosynthesis of mycolic acids to act as potential antituberculosis drugs.

Purification method for the isolation of monophosphate nucleotides from Champagne wine and their identification by mass spectrometry

Monophosphate nucleotides are difficult to identify in Champagne wine because they are present in small concentrations in a complex mixture. A method for the isolation, separation and identification of reference compounds, which achieved on average 79% recovery (except for cytidine derivatives), was developed and applied to wine. Some monophosphate nucleotides were then isolated from a Champagne wine aged on lees for 8 years, by ultrafiltration followed by a semi-preparative HPLC step using a strong anion-exchange column. The fraction obtained was subjected to HPLC in a reversed-phase column to remove the salt previously introduced, before identification of compounds by HPLC coupled to a mass spectrometer. For the first time in wine, 5'-IMP, 5'-AMP, 5'-CMP, 5'-GMP, 5'-UMP and the 3'- and/or 2'-isomers of the four latter compounds were identified by comparing their HPLC and electrospray ionization mass spectrometry data with those of reference nucleotides.

Direct characterization of isoquinoline alkaloids in a crude plant extract by ion-pair liquid chromatography-electrospray ionization tandem mass spectrometry: example of Eschscholtzia californica

An ion-pair HPLC-ESI-MS-MS method has been developed for the direct and rapid characterization of isoquinoline alkaloids in a crudely purified extract of the aerial parts of Eschscholtzia californica (Papaveraceae). This plant was chosen because of its increasing use in pharmaceutical industries and because its well known alkaloid composition allows the optimization of the experimental procedure through an on-line analytical sequence. Thus, 14 isoquinoline alkaloids of different types were detected and characterized. The identities of these compounds were confirmed unambigously by their fragmentation and UV spectra obtained by LC-diode-array detection. Various experiments including tandem mass spectrometry and in-orifice collision induced dissociation were performed and prove that MS-MS is a very efficient technique to identify these compounds. An explanation for each isoquinoline alkaloid type MS-MS fragmentation pattern is proposed and indicates similar neutral and/or radical losses. The order of the fragmentation depended on the type of compound but the lost fragments were similar.

An antioxidant sinapic acid ester isolated from Iberis amara

The isolation of 6-O-sinapoyl sucrose (1) from Iberis amara seeds and an evaluation of its antioxidative properties in comparison with sinapic acid and ascorbic acid are reported.

Influence of the nature of the porphyrin ligand on the nuclease activity of metalloporphyrin-oligonucleotide conjugates designed with cationic, hydrophobic or anionic metalloporphyrins

The synthesis of metalloporphyrin-oligonucleotide conjugates with different metalloporphyrin moieties are described as well as the comparison of their in vitro nuclease efficiency toward a single-stranded DNA target. Between cationic, anionic and hydrophobic manganese porphyrins covalently linked to the oligonucleotide, the best nuclease activity was obtained with the cationic ones, suggesting that the affinity of the cleaver to the DNA target is a key factor.