Modulation of Human Neutrophils’ Oxidative Burst by Hydroxylated 2-Styrylchromones: The Relevance of the Catechol Group

2-Styrylchromones (2-SC) are a group of oxygen-containing heterocyclic compounds, which are characterized by the attachment of a styryl group to the C-2 position of their chromone core. Over the years, several biological activities have been attributed to 2-SC, such as antioxidant, anti-inflammatory, antimicrobial, antiviral, and antitumor activities [1,2]. Nonetheless, there are no reports in the literature about the effect of 2-SC on human neutrophils’ oxidative burst. Therefore, the present study aims to evaluate the modulation of human neutrophils’ oxidative burst by a panel of hydroxylated 2-SC, previously obtained by chemical synthesis, and to analyze the structure–activity relationship [3]. For that purpose, freshly isolated neutrophils from human blood were stimulated with phorbol-12-myristate-13-acetate, and a chemiluminescence method was applied to evaluate the oxidative burst, using luminol as a probe [4]. Considering the OH substituents present on the B-ring of 2-SC, the tested compounds can be divided into the following three groups: group 1, with a catechol group (C-3′ and C-4′); group 2, with an OH at C-4′; group 3, without any substitution on the B-ring. The 2-SC from group 1 were the most active, with IC50 values in the order of 1 µM. In conclusion, the catechol B-ring appears to play an important role in the modulation of human neutrophils’ oxidative burst by 2-SC.

Inhibitory Effect of Lithospermic Acid on the HIV-1 Nucleocapsid Protein

The HIV-1 nucleocapsid protein (NC) is a desirable target in antiretroviral therapy due to its high conservation among HIV-1 strains, and to its multiple and crucial roles in the HIV-1 replication cycle. Natural products represent a valuable source of NC inhibitors, with the catechol group being a privileged scaffold in NC inhibition. By coupling molecular modeling with NMR spectroscopy and fluorescence-based assays, we disclosed lithospermic acid, a catechol derivative extracted from Salvia miltiorrhizza, as a potent and chemically stable non-covalent inhibitor of the NC. Being different from other catechol derivative reported so far, lithospermic acid does not undergo spontaneous oxidation in physiological conditions, thus becoming a profitable starting point for the development of efficient NC inhibitors.

A Rare Natural Benzo[k,l]xanthene as a Turn-Off Fluorescent Sensor for Cu2+ Ion

Rapid and efficient analyses of copper ions are crucial to providing key information for Cu2+ in living cells because of their biological importance. In this study, we reported one new turn-off fluorescent sensor for Cu2+ with a benzo[k,l]xanthene core, which served as an efficient cation sensor for copper ion over a wide range of other cations (Na+, K+, Ag+, Hg2+, Cd2+, Co2+, Ni2+, Zn2+, Mg2+, and Fe3+) owing to the catechol group in the aromatic core. The sensor showed selectivity for Cu2+ over other ions; the logKβ for Cu2+ binding to compound 1 had a value of 13.265. In the presence of Cu2+, sensor 1 provided significant fluorescence decrement; Co2+, and Ni2+ caused a fluorescence decrement when employed at a higher concentration than Cu2+, while Na+, K+, Hg2+, Cd2+, Zn2+, and Mg2+ metal ions produced only minor changes in fluorescence intensity. Fluorescence experiments demonstrate that compound 1 may have an application as a fluorescent probe for detecting Cu2+ with a limit of detection of 0.574 µM.

Proton trap effect on catechol–pyridine redox polymer nanoparticles as organic electrodes for lithium batteries

New redox-active polymer nanoparticles present that the redox potential of the catechol group is affected by the presence of the pyridine. This positive potential gain is associated to the proton trap effect, which benefits the performance of lithium-ion–polymer batteries.

Mn(ii) chelate-coated superparamagnetic iron oxide nanocrystals as high-efficiency magnetic resonance imaging contrast agents

In this communication, a paramagnetic bifunctional manganese(ii) chelate ([Mn(Dopa-EDTA)]2−) containing a catechol group is synthesized and coated on the surface of SPIO nanocrystals.

Magneto-optical Kerr effect characterization of a uniform nanocrystalline Fe3O4 monolayer fabricated on a silicon substrate functionalized with catechol groups

Magneto-optical devices can be fabricated by printing magnetic nanocrystals on a catechol-group-functionalized substrate; the process is macroscopically monolayer controlled.

A new route for the synthesis of phosphate esters: 2,2′-[benzene-1,2-diylbis(oxy)]bis(5,5-dimethyl-1,3,2-dioxaphosphinane) 2,2′-dioxide

Podand-type ligands are an interesting class of acyclic ligands which can form host–guest complexes with many transition metals and can undergo conformational changes. Organic phosphates are components of many biological molecules. A new route for the synthesis of phosphate esters with a retained six-membered ring has been used to prepare 2,2′-[benzene-1,2-diylbis(oxy)]bis(5,5-dimethyl-1,3,2-dioxaphosphinane) 2,2′-dioxide, C6H4{O[cyclo-P(O)OCH2CMe2CH2O]}2or C16H24O8P2, (1), 2-[(2′-hydroxybiphenyl-2-yl)oxy]-5,5-dimethyl-1,3,2-dioxaphosphinane 2-oxide, [cyclo-P(O)OCH2CMe2CH2O](2,2′-OC6H4–C6H4OH), (2), and oxybis(5,5-dimethyl-1,3,2-dioxaphosphinane) 2,2′-dioxide, O[cyclo-P(O)OCH2CMe2CH2O]2, (3). Compound (1) is novel, whereas the results for compounds (2) and (3) have been reported previously, but we record here our results for compound (3), which we find are more precise and accurate than those currently reported in the literature. In (1), twocyclo-P(O)OCH2CMe2CH2O groups are linked through a catechol group. The conformations about the two catechol O atoms are quite different,viz.one C—C—O—P torsion angle is −169.11 (11)° and indicates atransarrangement, whereas the other C—C—O—P torsion angle is 92.48 (16)°, showing agaucheconformation. Both six-membered POCCCO rings have good chair-shape conformations. In both thetransandgaucheconformations, the catechol O atoms are in the axial sites and the short P=O bonds are equatorially bound.