Antioxidant capacity of (+)-catechin visible-light photoirradiated in the presence of vitamin B2.

OBJECTIVES: Catechins are important components of human diet and have received special attention due to their antioxidant capacity. The purpose of this paper was to study the antioxidant action of (+)-catechin (CTQ) in the presence of vitamin B2 (riboflavin) as light-absorbing agent. Furthermore, two model compounds, catechol (CTC) and resorcinol (RSC), were selected in order to elucidate the reactive target of the CTQ molecule. The influence of pH-medium was investigated. METHODS: Stationary photolysis, polarographic detection of dissolved oxygen, reactive oxygen species (ROS)-scavengers, time-resolved near-IR phosphorescence detection, stationary, and time-resolved fluorescence and laser flash photolysis techniques were employed. RESULTS: CTQ interacts with riboflavin under visible-light photoirradiation as well as with different ROS which are generated in this mechanism. Radical-scavenging activity increases with increasing of pH-medium. DISCUSSION: pH-effect of the medium on radical-scavenging activity comes from the increased electron-donating ability of CTQ upon deprotonation. These results are very interesting due to the fact that the pH of the food products displays important variations. The [Formula: see text]-scavenging ability of CTQ, would be equal to the additive contribution of each reactive center, CTC, and RSC, present at the molecule of CTQ. However, CTQ would have a moderate ability to removal of [Formula: see text]-species at pH 7.

Vancomycin-sensitized photooxidation in the presence of the natural pigment vitamin B2: Interaction with excited states and photogenerated ROS.

Sensitized photooxidation processes in the presence of natural pigments may provide an alternative to antibiotics degradation since these compounds are transparent to natural light irradiation, therefore, they can be degraded by the action of photosensitizers which absorb light and produce highly reactive species, especially those derived from molecular oxygen (ROS). Most antibiotics used currently belong to a group of pharmaceutical substances that have been considered a new type of contaminants due to their persistence and bioaccumulation in the environment. OBJECTIVE: In this context, we decided to investigate the kinetic and mechanistic aspects of Vancomycin (Vanco) photosensitized degradation in the presence of the natural pigment Riboflavin (Vitamin B2, Rf) and the artificial dye Rose Bengal (RB) for comparative purposes. METHODS: The study have been done by using Stationary photolysis, Laser flash photolysis, Time-resolved phosphorence detection of O2(1Δg) experiments and Bactericidal activity evaluation. The experiments were carried out in aqueous solution at different pH values in order to establish relationships between the structure of the compound and its susceptibility to ROS-mediated photooxidation. RESULTS: Experimental evidence indicates that in the presence of Rf there is considerable contribution of the radical-mediated mechanism, while in the presence of RB the photooxidation process occurs exclusively through O2(1Δg) and the reactivity to this excited species increases with increasing pH of the environment. DISCUSSION: The results obtained, have been shown that Rf can raise the photodegradation of Vanco by both the radical pathway and the O2(1Δg) mediated. Furthermore, the antibiotic is able to interact with the excited electronic states of Rf as well as O2(1Δg) generated by energy transfer between the excited triplet state of the photosensitizer and the oxygen ground state. The predominant mechanism for photodegradation of Vanco in the presence of the Rf is the radical via because of the considerable interaction with the excited triplet state of the photosensitizer demonstrated by laser flash photolysis experiments. Microbiological test on Staphylococcus aureus ATCC25923 showed that the bactericidal activity of the antibiotic on the strain studied was affected by the sensitized photodegradation process, suggesting that photoproducts generated eventually do not retain the bactericidal properties of the original antibiotic.

Imported transmissible diseases in minors coming to Spain from low-income areas.

We prospectively studied the prevalence of imported transmissible diseases in 373 immigrant children and adolescents coming from Sub-Saharan Africa, North Africa and Latin America to Salamanca, Spain. The most frequent transmissible diseases in this group were latent tuberculosis (12.7%), chronic hepatitis B virus infection (4.2%), hepatitis C virus infection (2.3%), syphilis (1.5%) and human T-lymphotropic virus type 1 or 2 infections (1.4%). A total of 24.2% of patients had serologic profiles suggesting past hepatitis B virus infection. Anti-human immunodeficiency virus antibodies were not detected in any subject. Largely asymptomatic immigrant children show a high prevalence of communicable diseases. Thus, infectious disease screenings are highly advisable in immigrant children coming from low-income countries.

Interaction between Human Serum Albumin and antidiabetic compounds and its influence on the O2((1)Δg)-mediated degradation of the protein.

The complexity depicted by disease scenarios as diabetes mellitus, constitutes a very interesting field of study when drugs and biologically relevant components may be affected by such environments. In this report, the interaction between the protein Human Serum Albumin (HSA) and two antidiabetics (Andb), Gliclazide (Gli) and Glipizide (Glip) was studied through fluorescence and docking assays, in order to characterize these systems. On the basis that HSA and Andb can be exposed in vivo at high Reactive Oxygen Species (ROS) concentrations in diabetic patients, the degradative process of the protein free and bound to Andb, in presence of the species singlet molecular oxygen (O2((1)Δg)), was evaluated. Fluorescence and docking assays indicated that Gli, as well as Glip bind to HSA on two sites, with binding constants values in the order of 10(4)-10(5)M(-1). Likewise, docking assays revealed that the location of Gli or Glip on the protein may be the HSA binding sites II and III. Thermodynamic parameters showed that the interaction between HSA and Glip is a favored, enthalpically-controlled process. Oxygen uptake experiments indicated that Glip is less photooxidizable than Gli through a O2((1)Δg)-mediated process. Besides, the protein-Andb binding produced a decrease in the overall rate constant for O2((1)Δg) quenching as compared to the value for the free protein. This fact could be interpreted in terms of a reduction in the availability of Tyrosine residues in the bonded protein, with a concomitant decrease in the physical quenching deactivation of the oxidative species.

Kinetic and mechanistic aspects of sensitized photodegradation of ß-lactam antibiotics: microbiological implications.

Amoxicillin (Amx) and cephalexin (Cfx) are ß-lactam antibiotics widely used in human and veterinary medicine. Two points of interest surrounding these molecules are the photodegradation of the molecules and their microbiological implications, as well as the persistence and bioaccumulation in the environment which may cause resistance to bacterial strains. The kinetic and mechanistic aspects of the photosensitized degradation of Amx and Cfx have been studied in water at pH 7.4 and 10 by stationary and time-resolved methods. Kinetic evidence indicates that the Rose Bengal-sensitized photooxidation of Amx at pH 7.4 proceeds via O(2)((1)Δ(g)) and O(2•-) mechanisms while at pH 10 the degradation path occurs, principally, via O(2)((1)Δ(g)). For Cfx, this process is attributed to O(2)((1)Δ(g)) and O(2•-). Photoproducts, which arise from the addition of oxygen atoms and subsequent oxidation of the groups -CH(3) to -COOH, were detected. For both antibiotics the bacteriostatic activity decreases in parallel to their photodegradation. The results of this study could potentially help scientists to better understand and predict the photodegradability of these antibiotics on living organisms and in different environmental compartments.

Singlet molecular oxygen [O2(1Deltag)]-mediated photodegradation of tyrosine derivatives in the presence of cationic and neutral micellar systems.

The kinetics of rose bengal-sensitized photooxidation of tyrosine and several tyrosine-derivatives (tyr-D) named tyrosine methyl ester, tyrosine ethyl ester and tyrosine benzyl ester was studied in buffered pH 11 water, and buffered pH 11 micellar aqueous solutions of 0.01 M cetyltrimethylammonium chloride (CTAC) and 0.01 M-octylphenoxypolyethoxyethanol [triton X100 (TX100)]. Through time-resolved phosphorescence detection of singlet molecular oxygen (O(2)((1)Delta(g))) and polarographic determination of oxygen consumption, the respective bimolecular rate constants for reactive (k(r)) and overall (k(t)) quenching of the oxidative species by tyr-D were evaluated. Both rate constants behave in different fashion depending on the particular reaction medium. k(r)/k(t) values, increase in the sense CTAC<

[Analysis of the causes and predictive factors for discontinuing treatment with tenofovir in pretreated HIV patients]. / Análisis de las causas y factores predictivos de discontinuación del tratamiento con tenofovir en pacientes VIH pretratados.

OBJECTIVE: To determine the frequency and causes for discontinuing treatment with tenofovir and analyse possible predictive factors for changing this therapy in pretreated HIV patients. METHOD: A multi-centre, observational and retrospective study of all HIV patients undergoing treatment with tenofovir between July 2002 and December 2005. Data were obtained from databases for outpatients attending the three pharmacy departments participating in the study, and by reviewing clinical histories. The main sociodemographic, clinical and analytical variables at the start of treatment with tenofovir were collected. The causes for discontinuing treatment were classified as follows: adverse effects, virological failure, death and "other causes". A survival analysis was performed using the Kaplan-Meier method to analyse the possible predictive factors for discontinuing treatment. RESULTS: A total of 733 patients were included in the study and the median treatment period was 34.7 months. A total of 23.8% of patients discontinued treatment for the following reasons: adverse effects (43.2%), death (17.7%), virological failure (14.8%) and "other causes" (24.4%). There were 99 cases of lost to follow-up. In the survival analysis an association was found between normal serum creatinine values (p = 0.0042) at the start of treatment and the statistically significant probability of discontinuing treatment. CONCLUSIONS: Almost a quarter of the patients discontinued treatment with tenofovir during the study. The main cause for this was adverse effects. No association was found between any abnormal basal analytical parameter and a greater probability of discontinuing treatment.

Molecular epidemiology of drug-resistant Salmonella Typhimurium in Spain.

One hundred and forty-seven Salmonella serotype Typhimurium strains isolated in three provinces in the midwest of Spain were studied. Of these, 93.6% were drug resistant. There were two predominant resistance phenotypes: 43 isolates (29.3%) were resistant to amoxicillin, tetracyclines, chloramphenicol, streptomycin and sulphamethoxazole and 27 isolates (18.4%) to amoxicillin, amoxicillin/clavulanic acid, tetracyclines, chloramphenicol, streptomycin and sulphamethoxazole. Randomly amplified polymorphic DNA (RAPD) analysis and pulsed field gel electrophoresis (PFGE) were performed for molecular typing. Thirty-six DNA band profiles were differentiated by RAPD, and 38 by PFGE. We found a high level of clonality; 27% of strains were identical by both methods. There were additional smaller clonal lines within every area. The highest discriminatory power was obtained with PFGE, but the greatest degree of genetic diversity was observed among Salmonella Typhimurium using both RAPD and PFGE.

Hysteroscopic evaluation of endometrial polyps.

OBJECTIVE: To establish the validity of hysteroscopy for predicting cancer in endometrial polyps based on their number, size and hysteroscopic appearance. METHOD: Retrospective observational study of 653 women diagnosed hysteroscopically as having endometrial polyps. After outpatient or surgical hysteroscopic resection or resection following hysterectomy, the diagnosis was confirmed by histological examination. The incidence of cancer in women who had polyps was determined in the light of menopausal status, symptoms, size, number and appearance of the polyps. RESULT: Carcinoma was found in only 3.9% of the women who consulted for menopausal metrorrhagia and were diagnosed as having a polyp. Hysteroscopy had a sensitivity of 36% and a specificity of 98% for a diagnosis of cancerous polyp or atypical hyperplasia. CONCLUSION: The appearance and number of endometrial polyps seen by hysteroscopy may be useful in predicting cancer in the polyps, although resection and histological examination will still be necessary to confirm the diagnosis.

[An analisys fo causes for the discontinuation of a simplified antiretroviral regimen with abacavir, lamivudine and zidovudine]. / Análisis de las causas de suspensión del régimen antirretroviral simplificado abacavir, lamivudina y zidovudina.

OBJECTIVE: To identify and analyze the most common causes for the discontinuation of antiretroviral therapy, including the co-formulation of abacavir, lamivudine and zidovudine (ABC-3TC-AZT). METHOD: An observational, retrospective study was carried out on patients receiving antiretroviral therapy with ABC-3TC-AZT seen in the Pharmacy Department s outpatient unit from February 2002 through June 2004. The causes for discontinuation among patients withdrawing from this therapy were analyzed. Adherence was assessed using computerized dispensation records. A Kaplan-Meier survival analysis was designed in order to identify factors predictive of discontinuation. RESULTS: In all, 114 patients (85 males, 74.6%) received this therapy - 25.4% of them were naïve patients - and 34.2% (39/114) withdrew from this regimen, amongst them 44.8% (13/29) of naïve subjects. In 92.3% of cases this happened before treatment week 48. Discontinuation causes included: adverse reactions (46.1%), voluntary discontinuation (33.3%), clinical decision (15.4%), and other reasons (5.1%). A possible hypersensitivity reaction to ABC was reported for 9 patients. A greater likelihood of discontinuation was associated with detectable viral load at therapy onset, ex-parenteral drug abuser status, and naïve status (p < 0.05). CONCLUSIONS: A high percentage of discontinuations due to adverse events and voluntary withdrawal was found, particularly early during treatment. Patients who may therapeutically benefit from this regimen, particularly naïve subjects, should be identified, and interventions to improve adherence and optimize recovery parameters should be implemented.

Photodegradation of the herbicide Norflurazon sensitised by Riboflavin. A kinetic and mechanistic study.

The kinetics and mechanism of the Riboflavin (Rf)-promoted photochemical degradation with visible light of the herbicide Norflurazon (NF) has been studied by time-resolved and stationary techniques. Using light of wavelength higher than 400 nm--a region where NF is totally transparent--and with concentrations of Rf and NF of ca. 0.02 and 1 mM, respectively, only the excited triplet state of Rf ((3)Rf*) is quenched by NF, in competition with dissolved ground state triplet oxygen, O(2)((3)Sigma(g)(-)). NF degradation mainly occurs by reaction with superoxide radical anion O(2)(-) formed through two electron transfer steps: from NF to (3)Rf*, yielding Rf radical anion, and from this anion to O(2)((3)Sigma(g)(-)), regenerating ground state Rf. Although singlet molecular oxygen is also produced, NF only quenches this oxidative species in a physical mode. The global result is the photoprotection of the sensitiser and the photodegradation of NF.

[Antimicrobial drug resistance in non-typhi Salmonellae in Castilla y Leon]. / Resistencia a antimicrobianos en Salmonella no typhi en Castilla y León.

We studied the antibiotic susceptibility of 309 Salmonella isolates obtained from three hospitals serving the provinces of Salamanca, Avila and Zamora in the region of Castilla y Leon (mid-west Spain). The susceptibility to 18 antibiotics was studied using the agar dilution method, according to NCCLS guidelines, and the most common multiresistance phenotypes were determined for each province. We observed clear susceptibility differences between the two main serotypes found, S. enteritidis and S. typhimurium. Seventy percent of S. typhimurium were resistant to amoxicillin. In 44% of these isolates, amoxicillin resistance was associated with resistance to streptomycin, sulfonamides, tetracyclines and chloramphenicol. S. enteritidis was susceptible to most antibiotics tested; amoxicillin resistance was observed in 23.3%, and nalidixic acid resistance in 49.6%. Resistance to nalidixic acid was higher in S. enteritidis than in any other serotypes. According to NCCLS breakpoints, no strain was resistant to fluoroquinolones. However, according to MENSURA criteria, 9% of S. typhimurium isolates were resistant to ciprofloxacin. Resistance to cotrimazole and gentamicin was less than 10% for all the serotypes tested. The results indicate that S. typhimurium showed greater resistance and a high multidrug resistance rate. Conversely, S. enteritidis showed high resistance only to amoxicillin and nalidixic acid, though in most cases there was no correlation between this resistance and reduced susceptibility to fluoroquinolones.

[A study of erythropoietin use for myelodysplastic syndrome]. / Estudio de utilización de eritropoyetina en el síndrome mielodisplásico.

OBJECTIVES: To assess the effectiveness of erythropoietin (EPO) and to study the extent of application of published recommendations for use in treating anemia in patients with myelodysplastic syndrome (MDS). MATERIALS AND METHODS: An observational retrospective study of patients with MDS receiving at least one dose of EPO. Patients were selected from the outpatient database at the Pharmacy Department, and the medical history as well as both clinical and pharmacotherapeutic data were collected. The clinical effectiveness of EPO was assessed at 6, 12, 16 and 24 weeks after treatment using two distinct criteria for erythroid response. Three items were defined and assessed for each patient in order to establish the extent of application of published recommendations on the efficient use of EPO. RESULTS: Eleven patients were enrolled. Three of them responded to EPO at some point during follow-up, according to pre-defined criteria. All three items used in the assessment of the efficient use of EPO showed significantly high inadequacy rates. CONCLUSIONS: In our study, the effectiveness of EPO in the management of MDS-related anemia is similar to that described in the literature. However, upon the assessment of its use in our hospital, this drug was shown not to have been employed according to published recommendations, which promote its cost-effective use. We believe that the cooperation of the Pharmacy Department in the design of a protocol for EPO use in MDS is of interest, and would contribute to EPO's efficient use.

Mass spectrometric study of the photooxidation of the ophthalmic drugs timolol and pindolol.

A mass spectrometric study of the photooxidation products of the ophthalmic drugs pindolol (1-[1H-indol-4-yloxyl]-3-[isopropylamino]-2-propanol) and timolol (S-[-]-1-[t-butylamino]-3-[(4-morpholino-1,2,5-thiadiazol-3-yl)oxyl]-2-propanol) in water has been performed by LC-MS. Based on these data and the assumption that photooxidation mainly occurs through singlet molecular oxygen attack, a possible reaction mechanism is proposed. The mechanistic pathways involve singlet oxygen attack to the pindolol indole ring and oxidation of the pindolol isopropyl or timolol terbutyl methyl groups.

Kinetic study of the riboflavin-sensitised photooxygenation of two hydroxyquinolines of biological interest.

4-Hydroxyquinoline (4-OHQ) and 8-hydroxyquinoline (8-OHQ), two compounds of interest because of their bioactivity and their structural relation with bioactive products, are effectively photooxygenated when irradiated with visible light in the presence of riboflavin (Rf) (vitamin B2) in solution in air-saturated water-methanol (9:1). Rf behaves as a dye-sensitiser, since both quinolines are transparent to visible light. 8-OHQ degrades about five times faster than 4-OHQ. Kinetic data obtained through time-resolved and stationary detection of Rf-electronically excited states indicate that a superoxide radical anion-mediated mechanism exclusively operates for 4-OHQ, whereas singlet molecular oxygen--mainly--plus superoxide radical anion is the species that reacts with 8-OHQ. The sensitiser Rf, which is known to photodegrade under visible-light aerobic irradiation, is regenerated in the presence of any of the quinolines through an electron transfer process that produces superoxide radical anion. The overall picture indicates that both quinolines act as sacrificial scavengers of the photogenerated oxygen species, thus preventing the photodegradation of Rf.

Oxidation of di- and tripeptides of tyrosine and valine mediated by singlet molecular oxygen, phosphate radicals and sulfate radicals.

Kinetics and mechanism of the oxidation of tyrosine (Tyr) and valine (Val) di- and tripeptides (Tyr-Val, Val-Tyr and Val-Tyr-Val) mediated by singlet molecular oxygen [O(2)((1)Delta(g))], phosphate (HPO(4)(*-) and PO(4)(*2-)) and sulfate (SO(4)(*-)) radicals was studied, employing time-resolved O(2)((1)Delta(g)) phosphorescence detection, polarographic determination of dissolved oxygen and flash photolysis. All the substrates were highly photooxidizable through a O(2)((1)Delta(g))-mediated mechanism. Calculated quotients between the overall and reactive rate constants for the quenching of O(2)((1)Delta(g)) by Tyr-derivatives (k(t)/k(r) values, accounting for the efficiency of the effective photooxidation) were 1.3 for Tyr, 1 for Tyr-Val, 2.8 for Val-Tyr and 1.5 for Val-Tyr-Val. The effect of pH on the kinetics of the photooxidative process confirms that the presence of the dissociated phenolate group of Tyr clearly dominates the O(2)((1)Delta(g)) quenching process. Products analysis by LC-MS indicates that the photooxidation of Tyr di- and tripeptides proceeds with the breakage of peptide bonds. The information obtained from the evolution of primary amino groups upon photosensitized irradiation is in concordance with these results. Absolute rate constants for the reactions of phosphate radicals (HPO(4)(*-) and PO(4)(*2-), generated by photolysis of the P(2)O(8)(4-) at different pH) and sulfate radicals (SO(4)(*-), produced by photolysis of the S(2)O(8)(2-)) with Tyr peptides indicate that for all the substrates, the observed tendency in the rate constants is: SO(4)(*-) > or = HPO(4)(*-) > or = PO(4)(*2-). Formation of the phenoxyl radical of tyrosine was detected as an intermediate involved in the oxidation of tyrosine by HPO(4)(*-).

Dark and photoinduced interactions between Trolox, a polar-solvent-soluble model for vitamin E, and riboflavin.

The aerobic riboflavin (Rf)-sensitized visible-light irradiation of Trolox (TX), a polar-solvent-soluble model for vitamin E, has been studied employing stationary photolysis, polarographic detection of oxygen uptake, stationary and time-resolved fluorescence spectroscopy, and laser flash photolysis. Results indicate that in methanolic solution, no dark complexation exists between Rf and TX. The latter quenches singlet and triplet states of Rf, with rate constants of 6.2 x 10(9) M(-1) s(-1) and 4.7 x 10(9) M(-1) s(-1), respectively. The photodecomposition of Rf, a known process taking place from triplet Rf, has been found to depend on the concentration of dissolved TX: at >/=30 mM very slight Rf photodecomposition occurs due to the massive quenching of excited singlet Rf, while at TX concentrations < or =1 mM triplet Rf is photogenerated and subsequently quenched either by oxygen, giving rise to O(2)((1)Delta(g)), or by TX, yielding semireduced Rf through an electron transfer process. Complementary experiments performed in pure water employing superoxide dismutase and sodium azide inhibition of the oxygen uptake, in coincidence with flash photolysis data, indicate that superoxide anion and singlet molecular oxygen are generated, likely by the reaction of the anion radical from Rf with dissolved oxygen, also yielding neutral, ground state Rf or by energy transfer from triplet Rf to ground-state oxygen, respectively. The final result is that both TX and Rf are photodegraded, likely through oxidation with activated oxygen species. In the absence of oxygen no degradation of TX can be detected, but Rf photodegradation is favoured because Rf regeneration is avoided.