Organic synthesis of 1,2-dipalmitoyl-rac-glycero-3-phosphatidylethanolamine and its effect on the induction of apoptosis in normal human lung fibroblasts

BACKGROUND /OBJECTIVE

The phospholipid 1,2-dipalmitoyl-rac-glycero-3-phosphatidylethanolamine (PE) comprises two fatty acid chains: glycerol, phosphate, and ethanolamine. PE participates in critical cellular processes such as apoptosis and autophagy, which places it as a target for designing new therapeutic alternatives in diseases such as pulmonary fibrosis. Therefore, this study aimed obtain PE through a six-step organic synthesis pathway and determine its biological effect on apoptosis induction in normal human lung fibroblasts (NHLF).

METHODOLOGY

The first step of the organic synthesis route began with protected glycerol that was benzylated at sn-3; later, it was deprotected to react with palmitic acid at sn-1, sn-2. To remove the benzyl group, hydrogenation was performed with palladium on carbon (Pd/C); subsequently, the molecule was phosphorylated in sn-3 with phosphorus oxychloride and triethylamine, and the intermediate was hydrolyzed in an acid medium to obtain the final compound. After PE synthesis, apoptosis assessment was performed: apoptosis was induced using exposure to annexin V-FITC/propidium iodide-ECD (PI) and quantified using flow cytometry. The experiments were performed in three NHLF cell lines with different concentrations of PE 10, 100 and 1000 µg/mL for 24 and 48 h.

RESULTS

The PE obtained by organic synthesis presented a melting point of 190-192 °C, a purity of 95%, and a global yield of 8%. The evaluation of apoptosis with flow cytometry showed that at 24 h, exposure to PE 10, 100, and 1000 µg/mL induces early apoptosis in 19.42%- 25.54%, while late apoptosis was only significant P < 0.05 in cells challenged with 100 µg/mL PE. At 48 h, NHLF exposed to PE 10, 100, and 1000 µg/mL showed decreasing early apoptosis: 28.69-32.16%, 12.59-18.84%, and 10.91-12.61%, respectively. The rest of the NHLF exposed to PE showed late apoptosis: 12.03-16-42%, 11.04-15.94%, and 49.23-51.28%. Statistical analysis showed a significance P < 0.05 compared to the control.

CONCLUSION

The organic synthesis route of PE allows obtaining rac-1,2-O-Dipalmitoyl-glycero-3-phosphoethanolamine (1), which showed an apoptotic effect on NHLF.

(23R,231 S,25S)-231,26-Ep-oxy-23-ethyl-furost-20(22)-en-3β-ol

The title compound, C₂₉H₄₆O₃, is a steroid synthesized through a rearrangement of a sarsasapogenin derivative in acidic medium. The newly formed ring F is a tetra-hydro-2H-pyran heterocycle substituted by two methyl groups placed in equatorial positions. This ring displays a chair conformation, while di-hydro-furan ring E, to which it is bonded, has an envelope conformation. The mol-ecules are associated by weak O-H⋯O hydrogen bonds to form chains running in the [101] direction in the crystal.

Azasteroids from diosgenin: Synthesis and evaluation of their antiproliferative activity

In this work, we report the synthesis of two new azasteroids through the modification of the A and B rings of diosgenin 1. The 4-azasteroid derivative 12 was prepared in three steps using the α,β-insaturated-3-keto compound 11 as a precursor, which was first oxidized with KMnO₄/KIO₄ followed by an oxidative cleavage of ring A, and subsequently cyclized with an ammonium salt, under focused microwave irradiation for a short time of 3 min. A second azasteroid was synthesized, for which the key step was the Beckmann rearrangement of ring B of the oxime 16, affording the lactam-type enamide 17 in good yield. The methodologies developed for the synthesis of the precursors derivatives 10 and 11 contribute to improved yields, compared to those reported in the literature. The biological activity of the azasteroidal compounds 12 and 17 and their precursors has been evaluated in cervical cancer cells (HeLa), colon (HCT-15), and triple negative breast cancer (MDA-MB-231) lines.

Diosgenin-3,6-dione: second polymorph in space group P212121

A polymorphic modification of the title steroidal compound, derived from diosgenin, results from a conformational alteration for the A/B ring system.

The title steroid, [(25R)-spirost-4-en-3,6-dione, C₂₇H₃₈O₄], is obtained by oxidation of diosgenin, using the Jones reagent (CrO₃/H₂SO₄). The crystal structure was previously reported in space group P2₁2₁2₁, but nonetheless with the wrong absolute configuration and omitting positions for H atoms [Rajnikant et al. (2000 ▸). Mol. Cryst. Liq. Cryst. Sci. Technol. Sect. C, 12, 101–110]. The diffraction data set reported herein is for a second polymorph in the same space group, as evidenced by simulated powder patterns. Both forms are characterized by a similar ortho­rhom­bic unit cell, and a similar arrangement of the mol­ecules in the crystal structure. However, the conformation of the A/B rings in the steroid nucleus is slightly modified, leading to the observed polymorphism.

Mesoscale Assembly of Bisteroidal Esters from Terephthalic Acid

A new series of bisteroidal esters was synthesized using a spacer group, sterols and sapogenins as substrates. Steroidal dimers were prepared in high yields employing diesters of terephthalic acid as linkages at the 3β, 3'β steroidal positions. In all attempts to crystallize bisteroids, it was observed that the compounds tended to self-organize in solution, which was detected when employing various solvent systems. The non-covalent interactions (van der Waals) of the steroidal moieties of this series of symmetrical bisteroids, the polarity of the solvents systems, and the different solubilities of the bisteroid aggregates, indeed induce the molecules to self-assemble into supramolecular structures with well-defined organization. Our results show that the self-assembled structures for the bisteroidal derivatives depend on the solvent system used: with hexane/EtOAc, membrane-shaped structures were obtained, while pure EtOAc afforded strand-shaped arrangements. In the CHCl₃/CH₃OH system, thin strands were formed, since van der Waals interactions are lowered in this system, as a consequence of the increased solubility of the bisteroids in CHCl₃. Based on the characterization by SEM and XRD, we show evidence that the phenomenon of self-assembly of bisteroids occurs presenting different morphologies depending on the solvent used. The new steroidal dimer derivatives were characterized by NMR, TGA, DSC, SEM, and XRD. Finally, the molecular structure of one bisteroid was confirmed by single-crystal X-ray analysis.

(3β,5α,25R)-12-(Hydroxyimino)spirostan-3-yl acetate

The title steroid, C29H45NO5, obtained by condensation of hecogenin acetate [systematic name: (3β,5α,25R)-12-oxospirostan-3-yl acetate] with NH2OH, has the oxime group substituting the C-12 site on theCring of the steroid nucleus. The introduction of this functional group allows the formation of chain motifs, using the oxime OH group as a donor and the O atom of theEring as an acceptor. TheC(8) chains formed by this intermolecular hydrogen bond are oriented parallel to the short cell axisa. The structural features of this compound are very close to those of C29H43NO5, the derivative with a C14=C15 double bond in theDring, which crystallizes in the same space group and with similar unit-cell parameters.

Antiproliferative, Cytotoxic, and Apoptotic Activity of Steroidal Oximes in Cervicouterine Cell Lines

Steroidal sapogenins have shown antiproliferative effects against several tumor cell lines; and their effects on human cancer cells are currently under study. Changes in the functionality on the steroidal structure make it possible to modify the biological activity of compounds. Herein, we report the synthesis and in vitro antitumor activity of two steroidal oxime compounds on cervical cancer cells. These derivatives were synthesized from the steroidal sapogenin diosgenin in good yields. The in vitro assays show that the steroidal oximes show significant antiproliferative activity compared to the one observed for diosgenin. Cell proliferation, cell death, and the cytotoxic effects were determined in both cervical cancer cells and human lymphocytes. The cancer cells showed apoptotic morphology and an increased presence of active caspase-3, providing the notion of a death pathway in the cell. Significantly, the steroidal oximes did not exert a cytotoxic effect on lymphocytes.

(25R)-3β,16β-Diacetoxy-23-acetyl-22,26-epoxycholesta-5,22-dienen-hexane 0.8-solvate

In the title solvate, C33H48O6·0.8C6H14, the steroid presents a conformation almost identical to that of its previously characterized benzene monosolvate [Sandoval-Ramírezet al.(1999).Tetrahedron Lett.40, 5143–5146]. Then-hexane solvent of crystallization is agglomerated in channels parallel to [100] in the crystal. The solvent molecule is disordered over two sites in the asymmetric unit, with occupancies of 0.46 and 0.34. A minor disorder for the carbonyl O atom of the acetyl substituent at position 16 in the steroid was also introduced, with two sites having occupancies of 0.7 and 0.3.

Diosgenin hemihydrate

Diosgenin [or (22R,25R)-spirost-5-en-3β-ol] is the starting material of the Marker degradation, a cheap semi-synthesis of progesterone, which has been designated as an Inter­national Historic Chemical Landmark. Thus far, a single X-ray structure for diosgenin is known, namely its dimethyl sulfoxide solvate [Zhang et al. (2005 ▶). Acta Cryst. E61, o2324–o2325]. We have now determined the structure of the hemihydrate, C₂₇H₄₂O₃·0.5H₂O. The asymmetric unit contains two diosgenin mol­ecules, with quite similar conformations, and one water mol­ecule. Hy­droxy groups in steroids and water mol­ecules form O—H⋯O hydrogen-bonded R₅⁴(10) ring motifs. Fused edge-sharing R(10) rings form a backbone oriented along [100], which aggregates the diosgenin mol­ecules in the crystal structure.

Diosgenone: a second P2(1) polymorph

Diosgenone [(20S,22R,25R)-spirost-4-en-3-one, C₂₇H₄₀O₃] has been proposed as a new therapeutic alternative for the treatment of malaria. The first X-ray structure report for diosgenone was by Piro et al. [(2002). Z. Naturforsch. Teil C, 57, 947–950] in the space group P2₁ (Z′ = 2). We now report a new polymorph in the same space group, with two mol­ecules in the asymmetric unit. Both mol­ecules have similar conformations, characterized by a skewed envelope A ring, which contains the C=C bond conjugated with the ketone functionality at C3. The dimorphism results from a modification of the relative orientation of the mol­ecules in the asymmetric unit: two independent mol­ecules were arranged anti­parallel in the Piro report, while they are parallel in the present determination.

Stereospecific synthesis of new steroidal isoxazoles in dry media

An easy and fast procedure was developed for one-pot synthesis of steroidal isoxazoles starting from 23-acetylsapogenins derivatives in presence of P2O5/SiO2 in dry media under microwaves irradiation is described. Substrates of the 25S and 25R series were used as raw materials, establishing that this new methodology is applicable to both series.