Prins-Type Synthesis and SAR Study of Cytotoxic Alkyl Chloro Dihydropyrans

An efficient one-pot synthesis and docking studies of bioactive new antiproliferative dispiro[oxindole/acenaphthylenone‒benzofuranone] pyrrolidine scaffolds

A new and efficient method has been developed to synthesize dispiro[oxindole/acenaphthylenone-benzofuranone]pyrrolidine compounds. This is done by triggering the 1,3-dipolar cycloaddition reaction of azomethine ylides by reacting isatin/acenaphthoquinone with L-picolinic acid/L-proline/sarcosine/L-thioproline/tetrahydroisoquinolines, in a highly regioselective manner in an ionic liquid [DBU][Ac] with 4'-chloro-auron[2-(4-chlorobenzylidene)benzofuran-3(2H)-one]. Single-crystal X-ray diffraction data support the proposed structures of the new compounds. The heterocycles derived from amino acids such as L-picolinic acid, L-proline, and L-thioproline showed significant inhibitory effects against six human solid tumors, including lung, breast, cervix, colon, and others. These new structures were also tested in the active sites of the MDM2 receptor to further study their antiproliferative effects.

Lipophilic modification of salirasib modulates the antiproliferative and antimigratory activity

Salirasib, or farnesylthiosalicylic acid (FTS), is a salicylic acid derivative with demonstrated antineoplastic activity. While designed as a competitor of the substrate S-farnesyl cysteine on Ras, it is a potent competitive inhibitor of isoprenylcysteine carboxymethyl transferase. In this study, the antiproliferative activity on six different solid tumor cell lines was evaluated with a series of lipophilic thioether modified salirasib analogues, including those with or without a 1,2,3-triazole linker. A combination of bioassay, cheminformatics, docking, and in silico ADME-Tox was also performed. SAR analysis that analogues with three or more isoprene units or a long aliphatic chain exhibited the most potent activity. Furthermore, three compounds display superior antiproliferative activity than salirasib and similar potency compared to control anticancer drugs across all tested solid tumor cell lines. In addition, the behavior of the collection on migration and invasion, a key process in tumor metastasis, was also studied. Three analogues with specific antimigratory activity were identified with differential structural features being interesting starting points on the development of new antimetastatic agents. The antiproliferative and antimigratory effects observed suggest that modifying the thiol aliphatic/prenyl substituents can modulate the activity.

Zn(ii) complexes with thiazolyl–hydrazones: structure, intermolecular interactions, photophysical properties, computational study and anticancer activity

Title ligands and their symmetrical octahedral complexes are not photoluminescent, contrary to other synthesized asymmetrical complexes. In comparison to the ligands, the complexes showed improved antiproliferative activity and lower toxicity.

Design, Synthesis, and in vitro Evaluation of Tubulin-Targeting Dibenzothiazines with Antiproliferative Activity as a Novel Heterocycle Building Block

We prepared a series of free NH and N-substituted dibenzonthiazines with potential anti-tumor activity from N-aryl-benzenesulfonamides. A biological test of synthesized compounds (59 samples) was performed in vitro measuring their antiproliferative activity against a panel of six human solid tumor cell lines and its tubulin inhibitory activity. We identified 6-(phenylsulfonyl)-6H-dibenzo[c,e][1,2]thiazine 5,5-dioxide and 6-tosyl-6H-dibenzo[c,e][1,2]thiazine 5,5-dioxide as the best compounds with promising values of activity (overall range of 2-5.4 μM). Herein, we report the dibenzothiazine core as a novel building block with antiproliferative activity, targeting tubulin dynamics.

Synthesis and Evaluation of Pyrimidine Steroids as Antiproliferative Agents

A small and focused library of steroidal non-fused and fused pyrimidines was prepared from pregnenolone acetate and diosgenin, respectively. The key step was the cycloaddition reaction of nitrogen-containing 1,3-binucleophiles with the steroidal α,β-unsaturated ketone. Urea, thiourea and guanidine reacted in a similar manner and afforded the steroidal pyrimidines in good yields. The antiproliferative tests against human tumor cell lines gave GI₅₀ values in the micromolar range and had no effect on healthy fibroblasts. Additional experiments indicated that the compounds did not act as P-glycoprotein substrates, thus avoiding the rise of drug resistance. The fused steroidal pyrimidinethione was selected as drug lead for further testing due to its strong antiproliferative activities within the low micromolar range.

New pyrazolyl-dibenzo[b,e][1,4]diazepinones: room temperature one-pot synthesis and biological evaluation

Several new (5-aryloxy-pyrazolyl)- and (5-aryl/olefin-sulfanyl-pyrazolyl)-dibenzo[b,e] [1,4] diazepinone scaffolds have been synthesized, by assembling 5-substituted 3-methyl-1-phenyl-pyrazole-4-carbaldehydes of varied nature with different cyclic diketones and aromatic diamines successfully in the presence of indium chloride in acetonitrile, at room temperature. Desired products are excellent in the purity and isolated without chromatography. All new structures are confirmed, on the basis of single-crystal X-ray diffraction data of representative 29e. Compounds reported in the present work revealed good antioxidant, antimicrobial and antiproliferative activities with promising FRAP (ferric reducing antioxidant power), bacterial resistance and human solid tumor cell growth inhibitory values, respectively. Compounds 25c and 29e, overall, registered good to moderate activity against A549 (lung), HeLa (cervix), SW1573 (lung) T-47D (breast) and WiDr (colon) cell lines, with GI₅₀ values in the 2.6-5.1 μM and 1.8-7.5 μM ranges, respectively. Molecular docking was carried out to elucidate the binding modes of the compounds (25c, 29e) to topoisomerase I and II.

Biological Activities of Extracts from Aerial Parts of Salvia pachyphylla Epling Ex Munz

The antioxidant, antimicrobial, antiproliferative, and enzyme inhibitory properties of five extracts from aerial parts of Salvia pachyphylla Epling ex Munz were examined to assess the prospective of this plant as a source of natural products with therapeutic potential. These properties were analyzed by performing a set of standard assays. The extract obtained with dichloromethane showed the most variety of components, as they yielded promising results in all completed assays. Furthermore, the extract obtained with ethyl acetate exhibited the greatest antioxidant activity, as well as the best xanthine oxidase inhibitory activity. Remarkably, both extracts obtained with n-hexane or dichloromethane revealed significant antimicrobial activity against the Gram-positive bacteria; additionally, they showed greater antiproliferative activity against three representative cell lines of the most common types of cancers in women worldwide, and against a cell line that exemplifies cancers that typically develop drug resistance. Despite that, other extracts were less active, such as the methanolic or aqueous; their results are promising for the isolation and identification of novel bioactive molecules.

Selenazolyl-hydrazones as Novel Selective MAO Inhibitors With Antiproliferative and Antioxidant Activities: Experimental and In-silico Studies

The novel approach in the treatment of complex multifactorial diseases, such as neurodegenerative disorders and cancer, requires a development of efficient multi-targeting oriented drugs. Since oxidative stress significantly contributes to the pathogenesis of cancer and neurodegenerative disorders, potential drug candidates should possess good antioxidant properties. Due to promising biological activities shown for structurally related (1,3-thiazol-2-yl)hydrazones, a focused library of 12 structurally related benzylidene-based (1,3-selenazol-2-yl)hydrazones was designed as potential multi-targeting compounds. Monoamine oxidases (MAO) A/B inhibition properties of this class of compounds have been investigated. Surprisingly, the p-nitrophenyl-substituted (1,3-selenazol-2-yl)hydrazone 4 showed MAO B inhibition in a nanomolar concentration range (IC₅₀ = 73 nM). Excellent antioxidant properties were confirmed in a number of different in vitro assays. Antiproliferative activity screening on a panel of six human solid tumor cell lines showed that potencies of some of the investigated compounds was comparable or even better than that of the positive control 5-fluorouracil. In-silico calculations of ADME properties pointed to promising good pharmacokinetic profiles of investigated compounds. Docking studies suggest that some compounds, compared to positive controls, have the ability to strongly interact with targets relevant to cancer such as 5′-nucleotidase, and to neurodegenerative diseases such as the small conductance calcium-activated potassium channel protein 1, in addition to confirmation of inhibitory binding at MAO B.

New selenosteroids as antiproliferative agents

Starting from natural steroids (diosgenin, hecogenin, smilagenin, estrone), we have prepared a wide panel of selenoderivatives, including benzoselenazolones, selenosemicarbazones, isoselenocyanates, selenoureas, selenocyanates and diselenides, with the aim of developing new families of potential chemotherapeutic agents. The modification of the organoselenium moieties, and their position on the steroid provided valuable information concerning the antiproliferative activities. Among all the families accessed herein, the best profile was achieved for selenoureas on the A ring of estrone, which exhibited GI₅₀ values in the range 2.0-4.1 μM for all the tested tumor cell lines, with increased potency compared with commonly used chemotherapeutic agents, like 5-fluorouracil and cisplatin. Cell cycle analysis revealed that selenoureas induced accumulation of cells in the G₁ phase of the cell cycle in the breast cancer cell lines HBL-100 and T-47D; therefore, a different mechanism than cisplatin, that induces cell cycle accumulation in the S phase as a result of DNA damage, must be involved. In the rest of the tumor cells, a slight increase of the S compartment was observed. Moreover, selenosteoids turned out to be excellent glutathione peroxidase (GPx) mimics for the catalytic removal of deleterious H₂O₂ (t_1/2 8.0-22.5 min) and alkyl peroxides (t_1/2 23.0-38.9 min) when used in substoichiometric amounts (1% molar ratio), thus providing a valuable tool for reducing the intrinsic oxidative stress in tumor progression.

Chalcogen-containing phenolics as antiproliferative agents

Aim: The increasing number of cancer cases has stimulated researchers to seek for novel approaches. We have combined two bioactive moieties: a polyphenolic scaffold and an organoselenium motif. Four different families (isothiocyanates/thioureas, and their selenium isosters) derived from dopamine, (±)-norepinephrine and R-epinephrine were accessed. Results: Heterocumulenes derived from dopamine and β-O-methylnoradrenaline were strong antiproliferative agents (GI50<10 μM). Selenoureas derived from β-O-methylnoradrenaline bearing electron-withdrawing groups (halogen, -NO2, -Ph) on the phenyl ring, were also strong antiproliferative agents, besides exhibiting good antiradical and glutathione peroxidase-like activities. Up to a 14-fold increased activity was achieved compared with classical chemotherapeutic agents, exhibiting also different mechanisms of action (cell cycle assays). Redox analysis on HeLa cells suggested an increase of ROS levels after the incubation period. Conclusion: the combination of organoselenium and phenolic moieties might provide valuable lead compounds with relevant antiproliferative properties.

Antiproliferative activity of new 2-glyco-3-nitro-1,2-dihydroquinolines and quinolines synthesized under solventless conditions promoted by neutral alumina

This paper describes the syntheses of new 2-glyco-3-nitro-1,2-dihydroquinolines and 2-glyco-3-nitroquinolines by one-pot aza-Michael–Henry-dehydration reactions using green procedures, as well as the evaluation of their antiproliferative activity.

New tacrine dimers with antioxidant linkers as dual drugs: Anti-Alzheimer's and antiproliferative agents

We have designed a series of tacrine-based homo- and heterodimers that incorporate an antioxidant tether (selenoureido, chalcogenide) as new dual compounds: for the treatment of Alzheimer's disease and as antiproliferative agents. Symmetrical homodimers bearing a dichalcogenide or selenide-based tether, the best compounds in the series, were found to be strong and highly selective electric eel AChE inhibitors, with inhibition constants within the low nanomolar range. This high inhibitory activity was confirmed on recombinant human AChE for the most interesting derivatives. The three most promising homodimers also showed a good inhibitory activity towards amyloid-β self aggregation. The symmetric disulfide derivative bis[5-(1',2',3',4'-tetrahydroacridin-9'-ylamino)pentyl]disulfide (19) showed the best multipotent profile and was not neurotoxic on immortalized mouse cortical neurons even at 50 μM concentration. These results represent an improvement in activity and selectivity compared to parent tacrine, the first marketed drug against Alzheimer's disease. Title compounds also exhibited excellent in vitro antiproliferative activities against a panel of 6 human tumor cell lines, with GI₅₀ values within the submicromolar range for the most potent derivatives (0.12-0.95 μM); such values represent a spectacular increase compared to currently-used chemotherapeutic agents, such as 5-FU (up to 306-fold) and cisplatin (up to 162-fold). Cell cycle experiments indicated the accumulation of cells in the G₁ phase of the cycle, a different mechanism than the reported for cisplatin. The breast cancer cell lines turned out to be the most sensitive one of the panel tested.

Total synthesis of (+)-herboxidiene/GEX 1A

An efficient synthesis of herboxidiene is granted from highly stereoselective aldol reactions from two lactate-derived ketones and an oxa-Michael cyclization.

Synthesis and biological evaluation of crown ether acyl derivatives

A set of crown ethyl acyl derivatives based on 18-crown-6 moiety was synthesized and evaluated for biological activity. In vitro antiproliferative profiling demonstrated significant activities against HBL-100, HeLa, SW1573 and WiDr human cell lines. The most active compound exhibited GI₅₀ values in the range of 3.7-5.6μM. Antimicrobial evaluation showed that three polyaromatic compounds were active against Staphylococcus aureus (MIC₉₀ values from 8.3μM to 50μM), whereas a (decyloxy)benzene substitution exhibited moderate activity against Candida albicans (MIC₉₀ values 36μM). According to SAR evaluation, the size of the crown ether and the acyl side chain had a significant effect on the bioactivity. Aromatic moieties close to the acyl group led to improved bioactivity as exemplified by some of the tested compounds. These results provide further evidence on the potential of crown ethyl structure as a scaffold for developing new biological probes and lead candidates for drug development.

A catalyst- and solvent-free multicomponent synthesis and docking study of some new antiproliferative N5-allyl-quinolylpyrido[2,3-b][1,4]benzodiazepinone precursors

Heterocycles of this series resemble MDM2 inhibitors.

Antiproliferative and Structure Activity Relationships of Amaryllidaceae Alkaloids

The antiproliferative activity of a set of seven natural Amaryllidaceae alkaloids and 32 derivatives against four cancer cell lines (A2780, SW1573, T47-D and WiDr) was determined. The best antiproliferative activities were achieved with alkaloids derived from pancracine (2), haemanthamine (6) and haemantidine (7). For each skeleton, some structure-activity relationships were outlined.

Dienamine and Friedel-Crafts one-pot synthesis, and antitumor evaluation of diheteroarylalkanals

An asymmetric synthesis of diheteroarylalkanals through one-pot dienamine and Friedel-Crafts reaction is presented. The reaction tolerates a large variety of substituents at different positions of the starting aldehyde and also in the indole nucleophile, and a range of diheterocyclic alkanals can be achieved. Furthermore, we have studied the antiproliferative activity of these new compounds in representative cancer tumor cell lines.

Synthesis and bioactivity of Luffarin I

The first synthesis of Luffarin I, sesterterpenolide isolated from sponge Luffariella geometrica, has been accomplished from commercially available sclareol. The key strategy involved in this synthesis is the diastereoselective reduction of an intermediate ketone. Luffarin I against human solid tumor cell lines showed antiproliferative activities (GI₅₀) in the range 12–17 μM.

Synthesis and identification of unprecedented selective inhibitors of CK1ε

A small and structure-biased library of enantiopure anti-β-amino alcohols was prepared in a straightforward manner by a simplified version of the Reetz protocol. Antiproliferative activity testing against a panel of five human solid tumor cell lines gave GI50 values in the range 1-20 μM. The reverse screening by computational methods against 58 proteins involved in cancer pointed to kinases as possible therapeutic target candidates. The experimental determination of the interaction with 456 kinases indicated that the compounds behave as selective CK1ε inhibitors. Our results demonstrate that the lead compound represents the first selective CK1ε inhibitor with proven antiproliferative activity in cancer cell lines.

Phenolic thio- and selenosemicarbazones as multi-target drugs

A series of isosteric phenolic thio- and selenosemicarbazones have been obtained by condensation of naturally-occurring phenolic aldehydes and thio(seleno)semicarbazides. Title compounds were designed as potential multi-target drugs, and a series of structure-activity relationships could be established upon their in vitro assays: antioxidant activity, α-glucosidase inhibition and antiproliferative activity against six human tumor cell lines: A549 (non-small cell lung), HBL-100 (breast), HeLa (cervix), SW1573 (non-small cell lung), T-47D (breast) and WiDr (colon). For the antiradical activity, selenium atom and 2 or 3 phenolic hydroxyl groups proved to be essential motifs; remarkably, the compound with the most potent activity, with a trihydroxyphenyl scaffold (EC50 = 4.87 ± 1.57 μM) was found to be stronger than natural hydroxytyrosol, a potent antioxidant present in olive oil (EC50 = 13.80 ± 1.41 μM). Furthermore, one of the thiosemicarbazones was found to be a strong non-competitive inhibitor of α-glucosidase (Ki = 9.6 ± 1.6 μM), with an 8-fold increase in activity compared to acarbose (Ki = 77.9 ± 11.4 μM), marketed for the treatment of type-2 diabetes. Most of the synthesized compounds also exhibited relevant antiproliferative activities; in particular, seleno derivatives showed GI50 values lower than 6.0 μM for all the tested cell lines; N-naphthyl mono- and dihydroxylated derivatives behaved as more potent antiproliferative agents than 5-fluorouracil or cisplatin.

Efficient synthesis of some new antiproliferative N-fused indoles and isoquinolines via 1,3-dipolar cycloaddition reaction in an ionic liquid

Triethylammonium acetate (TEAA) as a new, recyclable and environmentally friendly reaction medium for the intramolecular[3+2] cycloaddition reaction.

A new iridoid, verbascoside and derivatives with inhibitory activity against Taq DNA polymerase

DNA polymerases are enzymes that play a crucial role in DNA metabolism such as replication, repair, transcription, recombination, and chromosome segregation during mitosis. Herein we report the isolation of a new iridoid (6-epi-catalpol, 2) and per-O-acetyl-verbascoside (11) from aerial part of Buddleja cordobensis Grisebach (Buddlejaceae). From compound 2, we have obtained eight compounds by chemical transformation. This group of compounds at a concentration of 500μM was assayed against Taq DNA polymerase. Compound 11 (per-O-acetyl-verbascoside) was the most active with an IC50 of 1.21±0.18μM; compounds 9, 2 and 8 were strong inhibitors with IC50 values of 5.57±0.70, 21.62±0.22 and 78.13±0.93μM, respectively. Compounds 11 and 9 could be a leader structures to development new anticancer chemotherapy medicines and a useful tool to investigate DNA polymerase activity.

Synthesis and antiproliferative activity of the heterobimetallic complexes [RuClCp(PPh₃)-μ-dmoPTA-1κP:2κ²N,N'-MCl₂] (M = Co, Ni, Zn; dmoPTA = 3,7-dimethyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane)

The synthesis and characterization of three novel heterobimetallic derivatives of general formula [RuClCp(PPh₃)-μ-dmoPTA-1κP:2κ²N,N'-MCl₂] (M = Co (1), Ni (2) and Zn (3), dmoPTA = 3,7-dimethyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane) are described. The sizes of their diffusing units are in agreement with the solid-state structures of 2 and 3, supporting a similar solid-state structure for complex 1. The diamagnetic ruthenium-zinc derivative 3 was fully characterized in solution at 193 K by NMR. Electrochemical properties of the complexes were investigated by cyclic voltammetry, supporting the influence of the {MCl₂} moiety on the electronic properties of the Ru-unit. For the three complexes the GI₅₀ values were in the range 0.8-6.5 μM and comparable to those of the standard anticancer drug cis-platin in the same cell lines.

Expanding the synthesis of new trans-sulfonamide platinum complexes: cytotoxicity, SAR, fluorescent cell assays and stability studies

In this manuscript, we describe the synthesis of new trans-N-sulfonamide platinum complexes and their antiproliferative activity (GI50, μM) in human solid tumors cells. The structure activity relationships (SAR), with different new synthesized complexes by variation in ligand, halogen and also in the stereochemistry of the ligand, has been studied. Solubility and stability studies have also been carried out as well as fluorescent cell assays in order to clarify the final target in the tumor cells.

Cytotoxic Bioactivity of Some Phenylpropanoic Acid Derivatives

In this study, we synthesized a series of phenylpropanoic acid derivatives based on modifications at four selected points of the molecular scaffold. The in vitro antiproliferative activities of the compounds were examined in representative human solid tumor cell lines. A SAR was established pointing out the relevance of the substituents. The best activity profiles were obtained for the derivatives bearing more lipophilic esters (GI50 3.1-21 μM).

Heterometallic platinum(II) compounds with β-aminoethylferrocenes: synthesis, electrochemical behaviour and anticancer activity

A new family of heterometallic compounds 3-6 containing ferrocenyl and platinum(II) centers has been synthesized by reaction of 1-β-aminoethylferrocene (1) and 1,1'-bis(β-aminoethyl)ferrocene (2) with Pt(II) precursors. Using K(2)[PtCl(4)] as the Pt(II) source, the cis-square-planar neutral compounds [Fe{η(5)-C(5)H(4)(CH(2))(2)NH(2)}(2)PtCl(2)] (3) and [{Fe(η(5)-C(5)H(4)(CH(2))(2)NH(2))(η(5)-C(5)H(5))}(2)PtCl(2)] (5) were obtained. Reaction of cis-[PtCl(2)(dmso)(2)] with 1 and 2 resulted in the displacement of dmso and chloride ligands from the platinum coordination sphere, affording the cationic and neutral compounds [Fe{η(5)-C(5)H(4)(CH(2))(2)NH(2)}(2)Pt(dmso)Cl]Cl (4) and [Fe(η(5)-C(5)H(4)(CH(2))(2)NH(2))(η(5)-C(5)H(5))Pt(dmso)Cl(2)] (6). Compounds 3-6 were thoroughly characterized using multinuclear ((1)H, (13)C, (195)Pt) NMR, IR spectroscopy, ESI mass spectrometry and elemental analysis. Single-crystal X-ray analysis of heterometallic 6 confirmed the cis geometry of the molecule and revealed that the platinum atom is held in a perfect square-planar geometry. The electrochemical behaviour of the heterometallic compounds 3-6, which has been examined by cyclic (CV) and square wave (SWV) voltammetries in dichloromethane and dmso solution, is characterized by the reversible one-electron oxidation of the ferrocene moieties. The results of the biological activity studies revealed that the organometallic complex 5 is active against all cell lines with GI(50) values in the range 1.7-2.3 μM. When compared to the standard anticancer drug cisplatin, heterotrimetallic 5, possessing two aminoethylferrocenyl units coordinated to the Pt(II) center, showed a greater activity profile in the colon cancer cell line. Cell cycle studies revealed that the new mixed compound exhibits a mechanism of action different to cisplatin.

New bicyclotridecane C15 nonterpenoid bromoallenes from Laurencia marilzae

Nonterpenoid bromoallenes possessing a novel skeleton that incorporates an unprecedented [5.5.1]bicyclotridecane ring system, marilzabicycloallenes A-D (1-4), were isolated from specimens of Laurencia marilzae collected on the Canary Islands. The framework of these metabolites strongly reinforces Braddock's hypothesis concerning the biosynthesis via electrophilic bromination of the obtusallene family.

Nonterpenoid C15 acetogenins from Laurencia marilzae

Eight new halogenated C(15) acetogenins, 1-8, were isolated from the organic extract of the red alga Laurencia marilzae. The structure elucidation and the assignments of the relative configurations were established by extensive use of spectroscopic studies, particularly 1D and 2D NMR data, while the absolute configurations of compounds 1 and 5 were determined by single-crystal X-ray diffraction analysis. Compounds 1, 2, 4, 5, and 7, along with the previously reported related cyclic ether obtusallene IV (9), were evaluated against six human solid tumor cell lines. All compounds were found to be essentially inactive (GI(50) > 10 μg/mL).

Cytotoxic Profile and Peculiar Reactivity with Biomolecules of a Novel "Rule-Breaker" Iodidoplatinum(II) Complex

Novel and surprising biological properties were disclosed for the platinum(II) complex cis-diiodidodiisopropylamineplatinum(II). Remarkably, this new platinum(II) complex manifests pronounced antiproliferative properties in vitro, in some cases superior to those of cisplatin. A peculiar reactivity with the model protein cytochrome c was indeed highlighted based on the loss of amine ligands and retention of iodides.

Antiproliferative activity of withanolides against human breast cancer cell lines

The in vitro antiproliferative activity of a series of 22 naturally occurring withanolides was examined against the T-47D, MCF7, MCF7/BUS, MDA-MB-231, and SK-Br-3 human solid tumor breast cancer cell lines. The most active compound showed GI(50) values in the range 0.16-0.71 muM. The aromatic withanolide 19 exhibited specific activity for the estrogen-receptor-positive cell lines (T-47D, MCF7, and MCF7/BUS). Overall, the results demonstrated the relevance of the substitution pattern on the A and B rings on the resultant antiproliferative activity.