Structure activity relationship studies on cytotoxicity and the effects on steroid receptors of AB-functionalized cholestanes

Novel neuroprotective 5,6-dihydropyrido[2',1':2,3]imidazo[4,5-c]quinoline derivatives acting through cholinesterase inhibition and CB2 signaling modulation

A novel group of 5,6-dihydropyrido [2',1':2,3]imidazo [4,5-c]quinolines was prepared via a microwave assisted one-pot telescopic approach. The synthetic sequence involves the formation of an amine precursor of imidazo [1,2-a]pyridine via condensation and reduction under microwave irradiation. Subsequently, the Pictet-Spengler cyclisation reaction occurs with ketones (cyclic or acyclic) to obtain substituted 5,6-dihydropyrido [2',1':2,3]imidazo [4,5-c]quinolines in excellent yields. The compounds were tested as neuroprotective agents. Observed protection of neuron-like cells, SH-SY5Y differentiated with ATRA, in Parkinson's and Huntington's disease models inspired further mechanistic studies of protective activity against damage induced by 1-methyl-4-phenylpyridinium (MPP+), a compound causing Parkinson's disease. The novel compounds exhibit similar or higher potency than ebselen, an established drug with antioxidant activity, in the cells against MPP + -induced total cellular superoxide production and cell death. However, they exhibit a significantly higher capacity to reduce mitochondrial superoxide and preserve mitochondrial membrane potential. We also observed marked differences between a selected derivative and ebselen in terms of normalizing MPP + -induced phosphorylation of Akt and ERK1/2. The cytoprotective activity was abrogated when signaling through cannabinoid receptor CB2 was blocked. The compounds also inhibit both acetylcholine and butyrylcholine esterases. Overall the data show that novel 5,6-dihydropyrido [2',1':2,3]imidazo [4,5-c]quinoline have a broad cytoprotective activity which is mediated by several mechanisms including mitoprotection.

Atropisomeric 1-phenylbenzimidazoles affecting microtubule organization: influence of axial chirality

Benzimidazoles are frequently used in medicinal chemistry. Their anticancer effect is among the most prominent biological activities exhibited by this scaffold. Although numerous benzimidazole derivatives have been synthesized, possible atropisomerism of ortho-substituted 1-phenylbenzimidazoles has been largely overlooked. The aim of this research was to synthesize a small library of novel atropisomeric benzimidazole derivatives and explore their biological activity in various cancer and normal human cell lines. The new unique structural motif provides an interesting 3D architecture with axial chirality, which further contributes to molecular complexity and specificity. Racemates and their separated atropisomers arrested the cell cycle, caused apoptosis, and affected microtubule organization in cancer cells in vitro at different intensities. Moreover, this phenomenon was also verified by the inhibition of endothelial cell migration. These results showed that (+)-atropisomers, especially 5n, exhibit a stronger effect and show promise as agents for cancer therapy.

Cytotoxic evaluation of new polyhydroxylated steroids from the Red Sea soft coral Litophyton mollis (Macfadyen, 1936)

An efficient column chromatography of the CH2Cl2/MeOH crude extract from the soft coral Litophyton mollis (Macfadyen, 1936) yielded seven steroids, including five 4α-methylated steroids (1-5) and two 19-oxygenated steroids (6-7). Notably, both compounds 3 and 7 are new, identified as (22E)-4α,24-dimethyl-5α-cholesta-22,24(28)-dien-3β,8β-diol (3) and (22E,24R)-7β-acetoxy-24-methyl-cholesta-5,22-dien-3β,19-diol (7). The chemical structures and relative configurations were elucidated through comprehensive spectroscopic analyses, including 1D and 2D NMR, as well as HRESIMS analysis. The cytotoxicity of metabolites 1-7 was evaluated against three cancer cell lines: MCF-7, HepG2, and NCI-1299. Remarkably, metabolites 6 and 7 exhibited strong cytotoxic activity against MCF-7, with IC50 values of 8.6 and 8.4 μM, respectively, while also showing moderate effects against NCI-1299, with IC50 values of 15.7 and 15.1 μM, respectively. Additionally, steroids 4 and 5 displayed weak cytotoxicity against all three cell lines, with IC50 values in the ranges of 34.7-37.5 and 30.8-46.3 μM, respectively.

Effect of modification of betulinic acid at the C3-carbon atom of homolupane triterpenoids on the antiproliferative activity in vitro

In search of new cytotoxic derivatives based on the lupane scaffold, methyl betulonate and methyl 20,29-dihydrobetulonate were conjugated with Reformatsky reagents to provide homolupanes extended at the C3-carbon atom. Further transformations of the functional groups afforded a series of derivatives with 2-hydroxyethyl and allyl alcohol moieties. Their varying antiproliferative activity in vitro was then investigated in four cancer cell lines and in normal human BJ fibroblasts. In cervical carcinoma HeLa cells, derivatives 5, 6 and 17 were the most promising with lower micromolar IC50s and no toxicity to fibroblasts, thus showing a high therapeutic index. In addition, induction of apoptosis was found in HeLa cells after 24 h treatment with compounds 5, 6, 13 and 29. This newly synthesized series is more interesting than the published lupane and homolupane triterpenes and saponins, due to their nontoxicity towards healthy human cells and stronger cytotoxicity to various cancer cell lines. This approach increases their potential as anticancer agents.

Seasonal variation of phenolic compounds in Zostera marina (Zosteraceae) from the Baltic Sea

Seasonal variations of phenolic compounds, in leaves of Zostera marina L. from the Baltic Sea near Kiel/Germany were investigated. Dominant compounds were mono- and disulfated flavonoids and phenylpropanoic acids, in particular luteolin 7,3'-O-disulfate and diosmetin 7-O-sulfate as well as rosmarinic acid, a dimeric phenylpropanoid. All detected sulfated flavones showed similar seasonal trends: there were two significant concentration peaks in June and November. Moreover, two geographically distinct flavonoid chemotypes were identified based on their respective main flavonoid; one chemotype was characterized by the prevalence of luteolin 7,3'-O-disulfate (German Baltic Sea), and the other by the prevalence of diosmetin 7-O-sulfate (Norwegian North Sea). Furthermore, an undescribed tetrameric phenylpropanoid, 7'',8''-didehydrosalvianolic acid B, was isolated and its structure was established by extensive NMR, MS, and CD experiments. This compound inhibited activity of Na⁺/K⁺-ATPase in the micro-molar range without any cytotoxic effects against human cancer and normal cells.

Novel pentacyclic triterpenes exhibiting strong neuroprotective activity in SH-SY5Y cells in salsolinol- and glutamate-induced neurodegeneration models

Novel triterpene derivatives were prepared and evaluated in salsolinol (SAL)- and glutamate (Glu)-induced models of neurodegeneration in neuron-like SH-SY5Y cells. Among the tested compounds, betulin triazole 4 bearing a tetraacetyl-β-d-glucose substituent showed a highly potent neuroprotective effect. Further studies revealed that removal of tetraacetyl-β-d-glucose part (free triazole derivative 10) resulted in strong neuroprotection in the SAL model at 1 μM, but this derivative suffered from cytotoxicity at higher concentrations. Both compounds modulated oxidative stress and caspase-3,7 activity, but 10 showed a superior effect comparable to the Ac-DEVD-CHO inhibitor. Interestingly, while both 4 and 10 outperformed the positive controls in blocking mitochondrial permeability transition pore opening, only 4 demonstrated potent restoration of the mitochondrial membrane potential (MMP) in the model. Derivatives 4 and 10 also showed neuroprotection in the Glu model, with 10 exhibiting the strongest oxidative stress reducing effect among the tested compounds, while the neuroprotective activity of 4 was probably due recovery of the MMP.

Cytokinin Plant Hormones Have Neuroprotective Activity in In Vitro Models of Parkinson's Disease

Cytokinins are adenine-based phytohormones that regulate key processes in plants, such as cell division and differentiation, root and shoot growth, apical dominance, branching, and seed germination. In preliminary studies, they have also shown protective activities against human neurodegenerative diseases. To extend knowledge of the protection (protective activity) they offer, we investigated activities of natural cytokinins against salsolinol (SAL)-induced toxicity (a Parkinson's disease model) and glutamate (Glu)-induced death of neuron-like dopaminergic SH-SY5Y cells. We found that kinetin-3-glucoside, cis-zeatin riboside, and N6-isopentenyladenosine were active in the SAL-induced PD model. In addition, trans-, cis-zeatin, and kinetin along with the iron chelator deferoxamine (DFO) and the necroptosis inhibitor necrostatin 1 (NEC-1) significantly reduced cell death rates in the Glu-induced model. Lactate dehydrogenase assays revealed that the cytokinins provided lower neuroprotective activity than DFO and NEC-1. Moreover, they reduced apoptotic caspase-3/7 activities less strongly than DFO. However, the cytokinins had very similar effects to DFO and NEC-1 on superoxide radical production. Overall, they showed protective activity in the SAL-induced model of parkinsonian neuronal cell death and Glu-induced model of oxidative damage mainly by reduction of oxidative stress.

Novel alkylaminoethyl derivatives of androstane 3-oximes as anticancer candidates: synthesis and evaluation of cytotoxic effects

Steroid anticancer drugs are the focus of numerous scientific research efforts. Due to their high cytotoxic effects against tumor cells, some natural or synthetic steroid compounds seem to be promising for the treatment of different classes of cancer. In the present study, fourteen novel O-alkylated oxyimino androst-4-ene derivatives were synthesized from isomerically pure 3E-oximes, using different alkylaminoethyl chlorides. Their in vitro cytotoxic activity was evaluated against eight human cancer cell lines, as well as against normal fetal lung (MRC-5) and human foreskin (BJ) fibroblasts, to test the efficiency and selectivity of the compounds. Most derivatives displayed strong activity against malignant melanoma (G-361), lung adenocarcinoma (A549) and colon adenocarcinoma (HT-29) cell lines. Angiogenesis was assessed in vitro using migration scratch and tube formation assays on HUVEC cells, where partial inhibition of endothelial cell migration was observed for the 17α-(pyridin-2-yl)methyl 2-(morpholin-4-yl)ethyl derivative. Among the compounds that most impaired the growth of lung cancer A549 cells, the (17E)-(pyridin-2-yl)methylidene derivative bearing a 2-(pyrrolidin-1-yl)ethyl substituent induced significant apoptosis in these cells. In combination with low cytotoxicity toward normal MRC-5 cells, this molecule stands out as a good candidate for further anticancer studies. In addition, in vitro investigations against cytochrome P450 enzymes revealed that certain compounds can bind selectively in the active sites of human steroid hydroxylases CYP7, CYP17A1, CYP19A1 or CYP21A2, which could be important for the development of novel activity modulators of these enzymes and identification of possible side effects.

Novel steroid O-alkylated 3-oxyimino derivatives were synthesized and evaluated in vitro for their antitumor properties. The obtained data indicate the potential of these functionalities for the development of new candidates for tumor treatment.

Synthesis and Biological Activity of Brassinosteroid Analogues with a Nitrogen-Containing Side Chain

Brassinosteroids are a class of plant hormones that regulate a broad range of physiological processes such as plant growth, development and immunity, including the suppression of biotic and abiotic stresses. In this paper, we report the synthesis of new brassinosteroid analogues with a nitrogen-containing side chain and their biological activity on Arabidopis thaliana. Based on molecular docking experiments, two groups of brassinosteroid analogues were prepared with short and long side chains in order to study the impact of side chain length on plants. The derivatives with a short side chain were prepared with amide, amine and ammonium functional groups. The derivatives with a long side chain were synthesized using amide and ammonium functional groups. A total of 25 new brassinosteroid analogues were prepared. All 25 compounds were tested in an Arabidopsis root sensitivity bioassay and cytotoxicity screening. The synthesized substances showed no significant inhibitory activity compared to natural 24-epibrassinolide. In contrast, in low concentration, several compounds (8a, 8b, 8e, 16e, 22a and 22e) showed interesting growth-promoting activity. The cytotoxicity assay showed no toxicity of the prepared compounds on cancer and normal cell lines.

Bioactive Steroids from the Red Sea Soft Coral Sinularia polydactyla

Six new (1, 2, 6, 8, 13, and 20) and twenty previously isolated (3-5, 7, 9-12, 14-19, and 21-26) steroids featuring thirteen different carbocycle motifs were isolated from the organic extract of the soft coral Sinularia polydactyla collected from the Hurghada reef in the Red Sea. The structures and the relative configurations of the isolated natural products have been determined based on extensive analysis of their NMR and MS data. The cytotoxic, anti-inflammatory, anti-angiogenic, and neuroprotective activity of compounds 3-7, 9-12, 14-20, and 22-26, as well as their effect on androgen receptor-regulated transcription was evaluated in vitro in human tumor and non-cancerous cells. Steroids 22 and 23 showed significant cytotoxicity in the low micromolar range against the HeLa and MCF7 cancer cell lines, while migration of endothelial cells was inhibited by compounds 11, 12, 22, and 23 at 20 µM. The results of the androgen receptor (AR) reporter assay showed that compound 11 exhibited the strongest inhibition of AR at 10 µM, while it is noteworthy that steroids 10, 16, and 20 displayed increased inhibition of AR with decreasing concentrations. Additionally, compounds 11 and 23 showed neuroprotective activity on neuron-like SH-SY5Y cells.

Design, synthesis and biological evaluation of novel 2-alkylidene 19-norcalcitriol analogs

Continuing our studies aimed at A-ring modified vitamin D compounds, we designed novel 19-norcalcitriol derivatives bearing at C-2 pegylated chains of different lengths. The terminal fragments of these substituents contain hydroxyls or moieties possessing nitrogen and/or sulfur atoms capable of transition metal ions complexation. Also, two conjugate-type platinum(II) complexes of 19-norcalcitriol were obtained in which l-methionine served as chelating moiety. The convergent synthesis of the target 19-norcalcitriol analogs involved several steps with the crucial one being condensation of A-ring phosphine oxide and the known Grundmann ketone by Wittig-Horner reaction. Further elaboration of the 2-alkylidene substituent provided all final compounds which were then tested to determine their affinity for the vitamin D receptor and cytotoxic activity.

Synthesis and evaluation of Na+/K+-ATP-ase inhibiting and cytotoxic in vitro activities of oleandrigenin and its selected 17β-(butenolidyl)- and 17β-(3-furyl)- analogues

Natural cardiac-active principles built upon the 14,16β-dihydroxy-5β,14β-androstane core and bearing a heterocyclic substituent at 17β, in particular, a cardenolide - oleandrin and a bufadienolide - bufotalin, are receiving a great deal of attention as potential anticancer drugs. The densely substituted and sterically shielded ring D is the particular structural feature of these compounds. The first synthesis of oleandrigenin from easily available steroid starting material is reported here. Furthermore, selected 17β-(4-butenolidyl)- and 17β-(3-furyl)-14,16β-dihydroxy-androstane derivatives were en route synthesized and examined for their Na⁺/K⁺-ATP-ase inhibitory properties as well as cytotoxic activities in normal and cancer cell lines. It was found that the furyl-analogue of oleandrigenin/bufatalin (7) and some related 17-(3-furyl)- derivatives (19, 21) show remarkably high Na⁺/K⁺-ATP-ase inhibitory activity as well as significant cytotoxicity in vitro. In addition, oleandrigenin 2 compared to derivatives 21 and 25 induced strong apoptosis in human cervical carcinoma HeLa cells after 24 h of treatment.

Synthesis of Gemini analogs of 19-norcalcitriol and their platinum(II) complexes

Hormonally active vitamin D₃ metabolite, calcitriol, plays an important role in calcium-phosphate homeostasis, immune system actions and cell differentiation. Although anticancer activity of calcitriol is well documented and thousands of its analogs have been synthesized, none has been approved as a potential drug against cancer. Therefore, we attempted to introduce the cytotoxic effect to the calcitriol molecule by its linking to cisplatin. Herein, we present the synthesis of vitamin D compounds, designed on the basis of molecular modeling and docking experiments to the vitamin D receptor, and characterized by the presence of significantly different two side chains attached to C-20. In this study, a new synthetic approach to Gemini analogs was developed. Preparation of the target 19-norcalcitriol compounds involved separate syntheses of several building blocks (the A-ring, C/D-rings and side-chain fragments). The convergent synthetic strategy was used to combine these components by the different coupling processes, the crucial one being Wittig-Horner reaction of the Grundmann ketone analog with the known 2-methylene A-ring phosphine oxide. Due to the nature of the constructed steroidal side chains (bidentate ligands), which allowed coordination of metal ions, the first conjugate-type platinum(II) complexes of the vitamin D analogs were also successfully prepared and characterized. The target vitamin D compounds, displaying significant affinity for a vitamin D receptor, were assessed in vitro for their anti-proliferative activities towards several cell lines.

New A-homo lactam D-homo lactone androstane derivative: Synthesis and evaluation of cytotoxic and anti-inflammatory activities in vitro

This paper describes the synthesis of a new A-homo lactam D-homo lactone androstane derivative from dehydroepiandrosterone. To evaluate the impact of the introduction of nitrogen in the parental scaffold on biological activity, a new androstane enamide-type lactam derivative was prepared and characterized. The new compound as well as starting compounds were screened for cytotoxic, anti-angiogenic and anti-inflammatory activities using several human cancer cell lines (MCF-7, MDA-MB-231, PC3, CEM, G-361, HeLa), endothelial (HUVEC) and non-tumour (MRC-5 and BJ) cell lines. Strong cytotoxic and anti-inflammatory activity with a broad therapeutical window was demonstrated by the A-homo lactam D-homo lactone androstane derivative. The induction of apoptosis in treated PC3 cultures was confirmed using apoptotic morphology screening and a fluorescent double-staining method. New A-homo lactam D-homo lactone androstane derivative induced apoptosis more than the tested reference compounds, Formestane and Doxorubicin. An in silico ADME analysis showed that the compounds possess drug-like properties.

Synthesis of New Cisplatin Derivatives from Bile Acids

A series of bile acid derived 1,2- and 1,3-diamines as well as their platinum(II) complexes were designed and synthesized in hope to get a highly cytotoxic compound by the combination of two bioactive moieties. All complexes obtained were subjected to cytotoxicity assays in vitro and some hybrid molecules showed an expected activity.

Sesquiterpene lactones from Sonchus palustris L. (Asteraceae, Cichorieae)

Seven previously undescribed sesquiterpene lactones, three known sesquiterpene lactones (ixerin D, 15-p-hydroxyphenylacetyllactucin, and 15-p-hydroxyphenylacetyllactucin-8-sulfate), and two known quinic acid derivatives (3-O-feruloylquinic acid and 3,5-di-O-caffeoylquinic acid) were isolated from Sonchus palustris L. roots. Four formerly undescribed compounds were elucidated to be 3β,14-dihydroxycostunolide-3-O-β-D-glucopyranosyl-(2-O-p-hydroxyphenylacetyl)-14-O-p-hydroxyphenylacetate, 15-p-methoxyphenylacetyllactucin, 15-p-methoxyphenylacetyllactucin-8-sulfate, and 8-p-hydroxyphenylacetyllactucin-15-sulfate. Additionally, three undescribed conjugates of lactucin and a eudesmanolide type sesquiterpenic acid, sonchpalustrin, 4″-O-methylsonchpalustrin, and isosonchpalustrin, were characterized. The structures of the newly discovered natural products were elucidated using 1D and 2D NMR spectroscopy and UHPLC-HRMS. 15-p-Hydroxyphenylacetyllactucin and 15-p-methoxyphenylacetyllactucin showed significant in vitro cytotoxicity against CEM and BJ cells with IC₅₀ values ranging from 3.9 to 9.8 μM. Compounds 3 and 4 showed also strong anti-inflammatory activity in vitro.

Synthesis, characterization and antiproliferative activity of seco analogues of brassinosteroids

Synthesis and structure-activity relationship analysis of a two groups of 2,3-seco analogues of brassinosteroids (BRs) were performed to examine their antiproliferative activities. Two steroid skeletons were chosen for the preparation of seco analogues - cholestane and stigmastane. The synthetic strategy consists of multistep reactions and detailed analysis of compounds prepared. We have discovered unpublished behaviour of 2,3-seco-2,3-dihydroxy-6-ketones leading to formation of intramolecular ketal with two new steroidal rings. Their reaction intermediates were also characterized in some cases. All compounds prepared were fully characterized with NMR and MS techniques. Most of compounds were tested for in vitro cytotoxicity on three cancer cell lines (CEM, MCF7, and HeLa) and normal human fibroblasts (BJ). It was discovered that some seco analogues caused apoptosis in cancer cells. The most promising seco derivative 28 proved to have high therapeutic index.

The synthesis of solasodine F-homo-analogues

An efficient synthesis of F-homosolasodine analogues containing the 5/7 spirohemiaminal moiety was elaborated. The method benefited from an easy opening of diosgenin F-ring and the introduction of a cyano group in position 26.

The novel brassinosteroid analog BR4848 inhibits angiogenesis in human endothelial cells and induces apoptosis in human cancer cells in vitro

We report the synthesis and detailed biological study of the synthetic brassinosteroid analog 2α,3α-dihydroxy-6-oxo-5α-androstan-17β-yl N-(tert-butoxycarbonyl)-D,L-valinate (BR4848). The panel of cancer cell lines was used for characterization of its antiproliferative activity, yet had no adverse effects in normal human fibroblasts. In HeLa cells, BR4848-induced apoptosis was accompanied by increase of apoptotic subG₁ cells, PARP-1 and caspase-7 fragmentation, downregulation of Bcl-2 and Mcl-1, an increase in caspase activity and G₂/M phase cell cycle arrest. Antiproliferative properties of BR4848 were exhibited by inhibition of phosphorylation of Akt, Erk1/2 and FAK. Furthermore, the developed analog exhibited in vitro antiangiogenic activity in human umbilical vein endothelial cells (HUVECs). BR4848-induced apoptosis accompanied with G₂/M arrest was detected in endothelial cells. BR4848 also inhibited adhesion, tube formation and migration of endothelial cells by inhibition of FAK, Erk 1/2, CDK5, VEGFR2, TNFα-stimulated production of IL-6, angiopoietin-2 and Jagged1. Finally, BR4848 did not modulate the activity nor nuclear translocation of any of the steroid receptors (ERα, ERβ, AR, MR and PR) included in reporter cell-based assays, which excludes the genomic activity of steroid receptors as a contributing factor to the observed biological activities of BR4848.

Design, synthesis and biological activities of new brassinosteroid analogues with a phenyl group in the side chain

We have prepared and studied a series of new brassinosteroid derivatives with a p-substituted phenyl group in the side chain. To obtain the best comparison between molecular docking and biological activities both types of brassinosteroids were synthesized; 6-ketones, 10 examples, and B-lactones, 8 examples. The phenyl group was introduced into the steroid skeleton by Horner-Wadsworth-Emmons. The docking studies were carried out using AutoDock Vina 1.05. Plant biological activities were established using different brassinosteroid bioassays in comparison with natural brassinosteroids. Differences in the production of the plant hormone ethylene were also observed in etiolated pea seedlings after treatment with new brassinosteroids. The most active compounds were lactone 8f and 6-oxo derivatives 8c and 9c, their biological activities were comparable or even better than naturally occurring brassinolide. Finally the cytotoxicity of the new derivatives was studied using human normal and cancer cell lines.