Diapocynin has been regarded as the active principle of apocynin, which is the most used inhibitor of NADPH oxidase. Here we performed a comprehensive study of the interaction of diapocynin with human serum albumin (HSA). We found that diapocynin binds with higher efficacy to site I of HSA and its binding constant (8.5x10 5 mol -1 L) was almost 100-fold higher compared to apocynin. By interacting with this chiral cavity of the protein, diapocynin became a chiral molecule, which was evidenced by its induced circular dichroism spectrum.The axial chirality was theoretically confirmed by searching the most stable conformations adopted by diapocynin using the Density Function Theory (DFT). The four minimum energy conformers, which presented dihedral angles of 58.00° and 302.00° (syn-aS and syn-aR enantiomers pair bearing 2,2'-dihydroxyl groups at the same side) and 132.86° and 227.14° (anti-aS and anti-aR enantiomers pair bearing 2,2'-dihydroxyl groups at opposite sides) were used as initial conformations for the docking simulations. The highest scored docking pose was obtained for site 1 and the dihedral angle resulted in 106.44°, i.e., an anti-aS chiral conformer. In conclusion, diapocynin is a strong ligand of HSA. An unprecedented combination of DFT calculation and docking simulation was used to explain the acquired chirality of diapocynin when bound to HSA.

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The application of zinc oxide (ZnO) nanoparticles in biomaterials has increased significantly in the recent years. Here, we aimed to study the potential deleterious effects of ZnO on blood components, including human serum albumin (HSA), erythrocytes and human isolated primary neutrophils. To test the influence of the morphology of the nanomaterials, ZnO nanoneedles (ZnO-nn) and nanoflowers (ZnO-nf) were synthesized. The zeta potential and mean size of ZnO-nf and ZnO-nn suspensions in phosphate-buffered saline were-10.73 mV and 3.81 nm and-5.27 mV and 18.26 nm, respectively. The incubation of ZnO with HSA did not cause its denaturation as verified by the absence of significant alterations in the intrinsic and extrinsic fluorescence and in the circular dichroism spectrum of the protein. The capacity of HSA as a drug carrier was not affected as verified by employing site I and II fluorescent markers. Neither type of ZnO was able to provoke the activation of neutrophils, as verified by lucigenin-and luminol-dependent chemiluminescence and by the extracellular release of hydrogen peroxide. ZnO-nf, but not ZnO-nn, induced the haemolysis of erythrocytes. In conclusion, our results reinforce the concept that ZnO nanomaterials are relatively safe for usage in biomaterials. A potential exception is the capacity of ZnO-nf to promote the lysis of erythrocytes, a discovery that shows the importance of the morphology in the toxicity of nanoparticles. Keywords Erythrocytes Á Human serum albumin Á Neutrophils Á Sonochemistry Á Zinc oxide nanoparticles Á Metal oxide nanoparticles Á Health effects

Titanium dioxide (TiO 2 ) and zinc oxide (ZnO) are among the most used catalysts in photodegradation. Paracetamol and salicylic acid are widely used as pharmaceutical drugs. We found that paracetamol is less susceptible to photodegradation compared to salicylic acid. From a chemical perspective, this was not expected since paracetamol is more vulnerable to chemical oxidation. Aiming the comprehension of this phenomenon, studies were performed comparing the efficiency of photodegradation of paracetamol versus salicylic acid and acetophenone versus 4-aminoacetophenone. The presence of amino/amide group decreased the efficiency of degradation significantly. It was also found that salicylic acid improved the degradation of paracetamol when both compounds were present in the reaction medium. The lower efficiency of photodegradation of the amino-based compounds seems to be related to the deactivation of the excited states of the TiO 2 and ZnO. Theoretical calculations at the TD-PBE0/6-311++G(3df,2p) high level were performed and corroborated our proposal.