Synthesis of zinc 13-oxime-functionalized chlorophyll-a derivatives and their (131E/Z)-dependent self-aggregation

Self-aggregation of zinc bacteriochlorophyll-d analogs with an acylhydrazone moiety as the 13-keto-carbonyl alternative

Zinc methyl 3-hydroxymethyl-pyropheophorbides-a possessing an acylhydrazinylidene group at the 131-position were prepared by chemically modifying chlorophyll-a, which were models of bacteriochlorophyll-d as one of the light-harvesting pigments in photosynthetic green bacteria. Similar to the self-aggregation of natural bacteriochlorophyll-d in the antenna systems called chlorosomes, some of the synthetic models self-aggregated in an aqueous Triton X-100 solution to give red-shifted and broadened visible absorption bands. The newly appeared oligomeric bands were ascribable to the exciton coupling of the chlorin π-systems along the molecular y-axis, leading to intense circular dichroism bands in the red-shifted Qy and Soret regions. The self-aggregation in the aqueous micelle was dependent on the steric size of the terminal substituent at the 13-acylhydrazone moiety. An increase in the length of the oligomethylene chain as the terminal moved the red-shifted Qy maxima to shorter wavelengths, and branched alkyl and benzyl substitutes afforded no more self-aggregates to leave monomeric species in the hydrophobic environment inside the micelle. These results indicated that the acyl groups on the 13-hydrazone as the alternative of the natural 13-ketone regulated the chlorosome-like self-aggregation.

Synthesis and Biological Activity of the Pyridine-Hexacyclic-Steroid Derivative on a Heart Failure Model

BACKGROUND

Several drugs with inotropic activity have been synthesized; however, there is very little information on biological activity exerted by steroid derivatives in the cardiovascular system.

OBJECTIVE

The aim of this research was to prepare a steroid-pyridine derivative to evaluate the effect it exerts on left ventricular pressure and characterize its molecular interaction.

METHODS

The first stage was carried out through the synthesis of a steroid-pyridine derivative using some chemical strategies. The second stage involved the evaluation of the biological activity of the steroid-pyridine derivative on left ventricular pressure using a model of heart failure in the absence or presence of the drugs, such as flutamide, tamoxifen, prazosin, metoprolol, indomethacin, and nifedipine.

RESULTS

The results showed that steroid-pyridine derivative increased left ventricular pressure in a dose-dependent manner (0.001-100 nM); however, this phenomenon was significantly inhibited only by nifedipine at a dose of 1 nM. These results indicate that positive inotropic activity produced by the steroid-pyridine derivative was via calcium channel activation. Furthermore, the biological activity exerted by the steroid-pyridine derivative on the left ventricle produces changes in cAMP concentration.

CONCLUSION

It is noteworthy that positive inotropic activity produced by this steroid-pyridine derivative involves a different molecular mechanism compared to other positive inotropic drugs. Therefore, this steroid could be a good candidate for the treatment of heart failure.