Oney Ramírez-Rodríguez

Mitochondria: A Promising Target for Anticancer Alkaloids

A great number of alkaloids exhibit high potential in cancer research. Some of them are anticancer drugs with well-defined clinical uses, exerting their action on microtubules dynamics or DNA replication and topology. On the other hand, mitochondria have been recognized as an essential organelle in the establishment of tumor characteristics, especially the resistance to cell death, high proliferative capacity and adaptation to unfavorable cellular environment. Interestingly, many alkaloids exert their anticancer activities affecting selectively some functions of the tumor mitochondria by 1) modulating OXPHOS and ADP/ATP transport, 2) increasing ROS levels and mitochondrial potential dissipation by crosstalk between endoplasmic reticulum (ER) and mitochondria, 3) inducing mitochondria-dependent apoptosis and autophagy, 4) inhibiting mitochondrial metabolic pathways and 5) by alteration of the morphology and biogenesis of this organelle. These antecedents show the relevance of developing research about the effects of alkaloids on functions controlled by tumor mitochondria, offering an attractive target for the design of new alkaloid derivatives, considering organelle- specific delivery strategies. This review describes mitochondria as a central component in the anticancer action of a set of alkaloids, in a way to illustrate the importance of this organelle in medicinal chemistry.

Electrochemical characterization of hydroquinone derivatives with different substituents in acetonitrile

The effect of carbonyl groups in the ortho position with respect to a hydroxyl group on the electrochemical oxidation of hydroquinones in acetonitrile is studied. The electrochemical response of hydroquinone on a glassy carbon electrode in 0.1 M tetrabutylammonium perchlorate was investigated in detail by voltammetry and coulometry. From these experiments, the oxidation potential was shifted to more positive values with respect to hydroquinone due to the presence of electron withdrawing groups bonded to the aromatic ring. For all compounds a diffusional behavior was observed, and the diffusion coefficient (D) of substituted hydroquinones was calculated showing higher values than found for unsubstituted hydroquinone. Theoretical calculations were carried out to gain insights into the intramolecular hydrogen bond present in these molecules affecting their electrochemical behavior. Relevant theoretical data are optimized geometrical parameters, HOMO energy, condensed radical Fukui functions (f°), natural charges, Wiberg bond orders (WBO), stabilization energies caused by electron transfer, and hyperconjugation stabilization energies from the NBO analysis. In most cases, the calculations show good agreement with experimental 1H-NMR data and support the electrochemical results.

NMR assignment in regioisomeric hydroquinones

A set of regioisomeric pairs of tricyclic hydroquinones, analogues of antitumor 9,10‐dihydroxy‐4,4‐dimethyl‐5,8‐dihydroanthracen‐1(4H)‐one (1) and other derivatives, were synthesized and their regiochemistry and NMR spectra assigned by using 1H‐detected one‐bond (CH) HMQC and long‐range CH HMBC, in good agreement with theoretical O3LYP/Alhrichs‐pVTZ calculations. The 5‐hydroxymethyl derivatives (11, 15, 19) showed a 3JH, H coupling constant of methylene protons evidencing the presence of a seven‐membered intramolecular hydrogen bonded ring, not observed for the 8‐hydroxymethyl isomers. Copyright

Electrospray ionization mass spectrometric fragmentation of hydroquinone derivatives

The fragmentation patterns of nine di-, tri- and tetracyclic hydroquinones with potential antitumor activity were rationalized by invoking competing mechanisms that included sterically accelerated homolytic cleavage, Meerwein-type rearrangements and dehydrations through elimination or intramolecular nucleophilic substitution.

8,8-Diethyl-1,4,5,8-tetra-hydro-naphthalene-1,4,5-trione

The title molecule, C14H14O3, contains two fused six-membered carbon rings with keto groups at positions 1, 4 and 5 and a gem-diethyl group at position 8. The molecule is close to planar (maximum deviation = 0.044 Å), with one ethyl group at each side of the molecular plane, with exception of the keto group at position 1 which is slightly deviated from the plane and disordered over two positions one on each side of it (occupancies 0.80/0.20). The packing of the molecule shows weak bonded chains along a through C—H⋯O contacts and two intramolecular C—H⋯O interactions are also present.

9,10-Dihydr­oxy-4,4-dimethyl-5,8-dihydro­anthracen-1(4H)-one

In the title molecule, C16H16O3, the ring system is planar and an intramolecular hydrogen bond is present. The molecular packing is dominated by an intermolecular hydrogen bond and by π-stacking interactions [interplanar separation 3.8012 Å].

4-Acetyl-3,3-diethyl-5-hydr­oxy-2-morpholino-2,3-dihydro-1-benzofuran

In the title compound, C18H25NO4, the benzofuran ring is almost planar and the morpholino ring displays a chair conformation. The packing of compound has a one-dimensional structure constructed through intermolecular O—H⋯O hydrogen bonds. The conformation is stabilized by intramolecular C—H⋯N and C—H⋯O interactions.