The formation of Fe3+-doxycycline complex is pH dependent: implications to doxycycline bioavailability.

The interactions of drugs with iron are of interest in relation to the potential effects of iron-rich foods and iron supplements on sorption and bioavailability. Doxycycline (DOX), a member of the tetracycline class of broad-spectrum antibiotics, is frequently administered by oral route. In the digestive tract, DOX can be exposed to iron at different pH values (stomach pH 1.5-4, duodenum pH 5-6, distal jejunum and ileum pH 7-8). In relation to this, we analyzed the impact of pH on Fe3+-DOX complex formation. The optimal conditions for Fe3+-DOX complex formation are pH = 4 and [Fe3+]/[DOX] = 6 molar ratio. HESI-MS showed that Fe3+-DOX complex has 1:1 stoichiometry. Raman spectra of Fe3+-DOX complex indicate the presence of two Fe3+-binding sites in DOX structure: tricarbonylamide group of ring A and phenolic-diketone oxygens of BCD rings. The Fe3+-DOX complex formed at pH = 4 is less susceptible to oxidation than DOX at this pH. The increase of pH induces the decomposition of Fe3+-DOX complex without oxidative degradation of DOX. The pH dependence of Fe3+-DOX complex formation may promote unwanted effects of DOX, impeding the absorption that mainly takes place in duodenum. This could further result in higher concentrations in the digestive tract and to pronounced impact on gut microbiota.

Effect of long-term drought on tomato leaves: the impact on metabolic and antioxidative response.

Water deficit triggers physiological, biochemical, and molecular changes in leaves that could be important for overall plant adaptive response and it can affect tomato yield and quality. To assess the influence of long-term moderate drought on leaves, four tomato accessions from MAGIC TOM populations were selected on the basis of their differences in fruit size and were grown in a glasshouse under control and water deficit conditions. Drought affected stomatal conductance more in large fruit genotypes compared to cherry genotypes and this could be related to higher abscisic acid (ABA) leaf content. Compared to large fruits, cherry tomato genotypes coped better with water stress by reducing leaf area and maintaining photochemical efficiency as important adaptive responses. Accumulation of soluble sugars in the cherry genotypes and organic acid in the leaves of the larger fruit genotypes indicated their role in the osmoregulation and the continuum of source/sink gradient under stress conditions. Long-term moderate drought induced upregulation of NCED gene in all four genotypes that was associated with ABA production. The increase in the expression of ZEP gene was found only in the LA1420 cherry genotype and indicated its possible role in the protection against photooxidative stress induced by prolonged water stress. In addition, upregulation of the APX genes, higher accumulation of vitamin C and total antioxidant capacity in cherry genotype leaves highlighted their greater adaptive response against long-term drought stress compared to larger fruit genotypes that could also reflect at fruit level. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12298-021-01102-2.

Influence of blackberry leaf extract on the copper corrosion behaviour in 0.5 M NaCl.

The research presented in this paper is focused on blackberry leaf extract (BLE) as a environmentally friendly corrosion inhibitor for copper in 0.5 M NaCl. The caffeic acid, quercetin-3-O-glucoside and kaempferol-3-O-glucoside were identified in BLE by using high-performance liquid chromatography (HPLC-DAD). The BLE functional groups were identified (ATR-FTIR). The electrochemical methods (potentiodynamic polarization, electrochemical frequency modulation and electrochemical impedance spectroscopy) show that BLE acts as a mixed type of inhibitor (max. IE is 97.19 %). The corrosion process is controlled by diffusion (BLE lower than 15 g/L) and charge transfer (15 g/L BLE).

Phenolics and Sesquiterpene Lactones Profile of Red and Green Lettuce: Combined Effect of Cultivar, Microbiological Fertiliser, and Season.

The main goal of our study was to find an optimal combination of tested factors to achieve lettuce rich in bioactive compounds sustaining its pleasant taste. We examined three red and three green cultivars in a greenhouse using two microbiological fertilisers (EM Aktiv and Vital Tricho), and their combination. Plants were grown in three consecutive growing seasons (autumn, winter, and spring). Lactones accumulated in autumn, whereas phenolics' concentration rose during winter. Red cultivars showed higher phenolics and lactone content, where chicoric acid and luteolin-7-glucoside were the most abundant in the 'Gaugin' winter trial. Lactucopicrin was the predominant lactone among tested cultivars with the highest value in the red cultivar 'Carmesi'. Solely applicated, the fertiliser EM Aktiv and Vital Tricho led to significantly higher phenolic acid and dihydrolactucopicrin content, while combined, there were notably increased levels of all detected lactones. Application of single fertilisers had no effect on flavonoid content, while the combination even reduced it. A sensory analysis showed a negative correlation between overall taste and total sesquiterpene lactones, lactucopicrin, caffeoylmalic, and chlorogenic acid, indicating a less bitter taste with decreasing content of these compounds. Our findings indicate that the cultivar, fertiliser, and growing season jointly affected all of the tested parameters, highlighting the differences in the application of EM Aktiv, Vital Tricho, and their combination.

The environmentally friendly approaches based on the heterojunction interface of the LaFeO3/Fe2O3@g-C3N4 composite for the disposable and laboratory sensing of triclosan.

Triclosan (TCS) is a polychlorinated phenoxy phenol (PCPPs) used as a disinfectant and a broad-spectrum antibacterial and antifungal agent in personal hygiene products. TCS easily forms diphenyl ethers and dioxins, which are persistent organic pollutants. This work used a double approach for the TSC sensing: a) screen-printed (SPE) electrochemical platform for on-site application, modified with lanthanum iron oxide and graphitic carbon nitride composite (LaFeO3/Fe2O3@g-C3N4/SPE); and b) carbon paste electrode (CPE), modified with the same material and used in laboratory conditions. Linear range from 0.1 µM to 10 µM, the limit of detection (LOD) of 29 nM and the limit of quantification (LOQ) of 91 nM were obtained for CP electrode in BRBS pH 8. SPE showed the best analytical parameters in BRBS at pH 3, with a linear range from 0.3 µM to 7 µM, LOD of 0.09 µM and LOQ of 0.28 µM. Furthermore, the influence of potential interferents was investigated and proven to be negligible. Determination of TSC was performed to estimate the environmental impact of this compound as well as the practical usefulness of the proposed sensor in the real sample analysis, confirmed with a HPLC analysis.

Coordination of hydralazine with Cu2+ at acidic pH promotes its oxidative degradation at neutral pH.

Hydralazine (HL), a frequently prescribed oral antihypertensive drug, shows redox interactions with transition metals such as copper that are not fully understood. Copper may be present at high concentrations in the digestive tract and can affect oral drugs. An important parameter for such interactions is pH, which changes from acidic in the gastric juice to neutral pH in intestines. In this study, we examined interactions of HL with Cu2+ ions in conditions that mimic pH shift in the digestive tract using UV-Vis, Raman and EPR spectroscopy, cyclic voltammetry and oximetry. In the acidic solution, Cu2+ formed a stable mononuclear complex with two bidentate coordinated HL molecules. On the other hand, at neutral pH, Cu2+ initiated oxidation and degradation of HL. The degradation was more rapid in the HL-Cu2+ system that was initially prepared at acidic pH and then shifted to neutral pH. The formation of the complex at acidic pH increases the availability of Cu2+ for redox reactions after the shift to neutral pH at which Cu2+ is poorly soluble. These results imply that the change of pH along the digestive tract may promote HL degradation by allowing the formation of the complex at gastric pH which makes Cu2+ available for subsequent oxidation of HL at neutral pH.

Modulatory role of nitric oxide in cardiac performance.

Nitric oxide is produced by almost all cardiac cells, endothelial cells, cardiomyocytes and nerve fibers. It is synthesized by an enzyme, a nitric oxide synthase, which occurs in endothelial, neural and inducible form. The distribution of nitric oxide synthase in the heart is characterized by a pronounced non-uniformity. Nitric oxide exerts its effects in physiological and pathophysiological conditions. The physiological effects of low concentrations of nitric oxide, which is released in the normal conditions under the influence of constituent enzymes, occur via cyclic guanosine monophosphate. The synthesized nitric oxide exhibits its effect in the cells where it is produced, in an autocrine manner, or by diffusing into the neighboring cells, in a paracrine manner. Nitric oxide acts by regulating the coronary vessel tonus, affecting the contractility of cardiomyocytes, generating an inotropic effect in a dose-dependent manner and controlling the cellular respiration. Other effects of nitric oxide in the cardiovascular system include the hyperpolarization of the smooth muscle cells in blood vessels, the inhibition of the monocyte adhesion, the inhibition of platelet migration, adhesion and aggregation and the proliferation of smooth muscle cells and fibroblasts. The anti-atherosclerotic effects of nitric oxide are based on these effects. Nitric oxide is a weak free radical in gaseous state, and the cytotoxic and/or the cytoprotective effects of the higher concentrations of nitric oxide are related to the chemical structure of nitric oxide as a free radical. The excessive production of nitric oxide by the activation of inducible nitric oxide synthase can lead to major irregularities in the function of cardiomyocytes and cardiac insufficiency. Understanding the nitric oxide molecular mechanisms of signaling pathways in the heart can provide a new strategic approach to prevention and treatment of cardiovascular diseases.