Person: Olives Barba, Ana Isabel
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First Name
Ana Isabel
Last Name
Olives Barba
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Farmacia
Department
Química en Ciencias Farmacéuticas
Area
Química Analítica
Identifiers
5 results
Search Results
Now showing 1 - 5 of 5
Item Eco-friendly liquid chromatographic separations based on the use of cyclodextrins as mobile phase additives(Green Chemistry, 2011) González Ruiz, Víctor; León Leal, Andrés Gerardo; Menéndez Ramos, José Carlos; Martín Carmona, María Antonia; Olives Barba, Ana IsabelAcetonitrile and methanol are the most popular solvents employed in analytical HPLC, but they suffer from a number of drawbacks from the environmental point of view. Alternative, greener mobile phases employing methanol or the less toxic solvent ethanol as the sole organic solvent are proposed in this paper, and applied to the problem of the separation of b-carbolines on C18-stationary phases. The use of b-cyclodextrin (b-CD) and (2-hydroxypropyl)-b-cyclodextrin (HPb-CD) as mobile phase additives allowed us to increase the proportion of water in the mobile phases without loss in the resolution or efficiency of the separations, leading initially to a considerable reduction of the proportion of methanol in the mobile phase (from 70% to 50%) and at a later stage, to the development of a mobile phase containing only 30% of ethanol. The b-carboline–cyclodextrin association constants were determined by HPLC, and the inclusion complexes were also characterized by 1 H-NMR, 13C-NMR and 2D-ROESY experiments, and these studies were used to explain the chromatographic behaviour. The new chromatographic methodology developed was validated and applied to the quantitation of b-carboline derivatives in spiked human serum samples. For the extraction of b-carboline alkaloids from serum samples, liquid–liquid extraction (LLE) and solid-phase extraction (SPE) procedures were compared. It was concluded that the combination of a pre-treatment procedure (ionic exchange SPE) with a water-enriched chromatographic separation leads to a promising, environmentally friendly new methodology.Item Bisavenathramide Analogues as Nrf2 Inductors and Neuroprotectors in In Vitro Models of Oxidative Stress and Hyperphosphorylation(Antioxidants, 2021) Cores Esperón, Ángel; Abril Comesaña, Sheila; Michalska Dziama, Patrycja; Duarte, Pablo; Olives Barba, Ana Isabel; Martín Carmona, María Antonia; Villacampa Sanz, Mercedes; León Martínez, Rafael; Menéndez Ramos, José CarlosOxidative stress is crucial to the outbreak and advancement of neurodegenerative diseases and is a common factor to many of them. We describe the synthesis of a library of derivatives of the 4-arylmethylen-2-pyrrolin-5-one framework by sequential application of a three-component reaction of primary amines, β-dicarbonyl compounds, and α-haloketones and a Knoevenagel condensation. These compounds can be viewed as cyclic amides of caffeic and ferulic acids, and are also structurally related to the bisavenanthramide family of natural antioxidants. Most members of the library showed low cytotoxicity and good activity as inductors of Nrf2, a transcription factor that acts as the master regulator of the antioxidant response associated with activation of the antioxidant response element (ARE). Nrf2-dependent protein expression was also proved by the significant increase in the levels of the HMOX1 and NQO1 proteins. Some compounds exerted neuroprotective properties in oxidative stress situations, such as rotenone/oligomycin-induced toxicity, and also against protein hyperphosphorylation induced by the phosphatase inhibitor okadaic acid. Compound 3i, which can be considered a good candidate for further hit-to-lead development against neurodegenerative diseases due to its well-balanced multitarget profile, was further characterized by proving its ability to reduce phosphorylated Tau levels.Item Fluorescence properties of the anti-tumour alkaloid luotonin A and new synthetic analogues: pH modulation as an approach to their fluorimetric quantitation in biological samples(Journal of Luminescence, 2012) González Ruiz, Víctor; González-Cuevas, Yamisley; Arunachalam, Sankaralingam; Martín Carmona, María Antonia; Olives Barba, Ana Isabel; Ribelles, Pascual; Ramos García, María Teresa; Menéndez Ramos, José CarlosLuotonin A is an alkaloid structurally related to the natural anti-tumour agent camptothecin. The fluorescence behaviour of luotonin A and a series of six analogues is described in the present work. The influence of solvent polarity and pH on the native fluorescence properties of these alkaloids was studied, finding that in organic solvents or in aqueous solutions (pH 5.5–7.2) the neutral form of the luotonin derivatives emit in the region of 410–450 nm but, in both media, acidification to pH values below 3.0 causes a new emission band to appear at about 500 nm. An ESPT reaction occurs due to the protonation of the basic nitrogen atoms of the pentacyclic ring. Acid-base titrations of luotonin A and its derivatives in aqueous and acetonitrile media were carried out in order to determine their pKa n values which were around 2, showing these compounds to be very weak bases. In aqueous media, the absence of an iso-emissive point in the emission spectra suggests the existence of more than two species in the proton transfer equilibria. The basicity of the luotonin A derivatives is increased in organic media, and a good correlation between the pKa n values and the chemical structure was found. The protonation of luotonin A was also studied by 1 H-NMR and 13C-NMR experiments, which proved the protonation of the nitrogen atoms at the positions 5 and 6 of the pentacyclic ring. The fluorescence quantum yields were determined in ethanol and in aqueous solutions under neutral and acidic conditions. The fluorescence quantum yields were higher in water for the case of the more polar compounds, and the opposite result was obtained for the more hydrophobic ones. The remarkable and interesting fluorescence properties of luotonin A prompted the development of its fluorimetric analytical quantitation, obtaining very good analytical featuresItem Fluorescence Sensors Based on Hydroxycarbazole for the Determination of Neurodegeneration-Related Halide Anions(Biosensors, 2022) González Ruiz, Víctor; Cores, Ángel; Caja, M. Mar; Sridharan, Vellaisamy; Villacampa, Mercedes; Martín, M. Antonia; Olives Barba, Ana Isabel; Menéndez Ramos, José CarlosThe environmental presence of anions of natural origin or anthropogenic origin is gradually increasing. As a tool to tackle this problem, carbazole derivatives are an attractive gateway to the development of luminescent chemosensors. Considering the different mechanisms proposed for anion recognition, the fluorescence properties and anion-binding response of several newly synthesised carbazole derivatives were studied. Potential anion sensors were designed so that they combined the native fluorescence of carbazole with the presence of hydrogen bonding donor groups in critical positions for anion recognition. These compounds were synthesised by a feasible and non-expensive procedure using palladium-promoted cyclodehydrogenation of suitable diarylamine under microwave irradiation. In comparison to the other carbazole derivatives studied, 1-hydroxycarbazole proved to be useful as a fluorescent sensor for anions, as it was able to sensitively recognise fluoride and chloride anions by establishing hydrogen bond interactions through the hydrogen atoms on the pyrrolic nitrogen and the hydroxy group. Solvent effects and excited-state proton transfer (ESPT) of the carbazole derivatives are described to discard the role of the anions as Brönsted bases on the observed fluorescence behaviour of the sensors. The anion–sensor interaction was confirmed by 1H-NMR. Molecular modelling was employed to propose a mode of recognition of the sensor in terms of complex stability and interatomic distances. 1-hydroxycarbazole was employed for the quantitation of fluoride and chloride anions in commercially available medicinal spring water and mouthwash samples.Item Enhanced Stability and Bioactivity of Natural Anticancer Topoisomerase I Inhibitors through Cyclodextrin Complexation(Pharmaceutics, 2021) González Ruiz, Víctor; Cores Esperón, Ángel; Martín Cámara, Olmo; Serrano Orellana, Karen; Michalska Dziama, Patrycja; Cervera Carrascón, Víctor Enrique; León Martínez, Rafael; Olives Barba, Ana Isabel; Martín Carmona, María Antonia; Menéndez Ramos, José CarlosThe use of cyclodextrins as drug nano-carrier systems for drug delivery is gaining importance in the pharmaceutical industry due to the interesting pharmacokinetic properties of the resulting inclusion complexes. In the present work, complexes of the anti-cancer alkaloids camptothecin and luotonin A have been prepared with β-cyclodextrin and hydroxypropyl-β-cyclodextrin. These cyclodextrin complexes were characterized by nuclear magnetic resonance spectroscopy (NMR). The variations in the 1H-NMR and 13C-NMR chemical shifts allowed to establish the inclusion modes of the compounds into the cyclodextrin cavities, which were supported by docking and molecular dynamics studies. The efficiency of the complexation was quantified by UV-Vis spectrophotometry and spectrofluorimetry, which showed that the protonation equilibria of camptothecin and luotonin A were drastically hampered upon formation of the inclusion complexes. The stabilization of camptothecin towards hydrolysis inside the cyclodextrin cavity was verified by the quantitation of the active lactone form by reverse phase liquid chromatography fluorimetric detection, both in basic conditions and in the presence of serum albumin. The antitumor activity of luotonin A and camptothecin complexes were studied in several cancer cell lines (breast, lung, hepatic carcinoma, ovarian carcinoma and human neuroblastoma) and an enhanced activity was found compared to the free alkaloids, particularly in the case of hydroxypropyl-β-cyclodextrin derivatives. This result shows that the cyclodextrin inclusion strategy has much potential towards reaching the goal of employing luotonin A or its analogues as stable analogues of camptothecin.