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Kinetically inert platinum(IV) complexes are a chemical strategy to overcome the impediments of standard platinum(II) antineoplastic drugs like cisplatin, oxaliplatin and carboplatin. In this study, we reported the syntheses and structural characterisation of three platinum(IV) complexes that incorporate 5-benzyloxyindole-3-acetic acid, a bioactive ligand that integrates an indole pharmacophore. The purity and chemical structures of the resultant complexes, P-5B3A , 5-5B3A and 56-5B3A were confirmed via spectroscopic means. The complexes were evaluated for anticancer activity against multiple human cell lines. All complexes proved to be considerably more active than cisplatin, oxaliplatin and carboplatin in most cell lines tested. Remarkably, 56-5B3A demonstrated the greatest anticancer activity, displaying GI 50 values between 1.2 and 150 nM. Enhanced production of reactive oxygen species paired with the decline in mitochondrial activity as well as inhibition of histone deacetylase were also demonstrated by the complexes in HT29 colon cells.

Cisplatin-type covalent chemotherapeutics are a cornerstone of modern medicinal oncology. However, these drugs remain encumbered with dose-limiting side effects and are susceptible to innate and acquired resistance. The bulk of platinum anticancer research has focused on Cisplatin and its derivatives. Here, we take inspiration from the design of platinum complexes and ligands used successfully with other metals to create six novel complexes. Herein, the synthesis, characterization, DNA binding affinities, and lipophilicity of a series of non-traditional organometallic Pt(II)-complexes are described. These complexes have a basic [Pt(P L )(A L )]Cl 2 molecular formula which incorporates either 2-pyrrolidin-2-ylpyridine, 2-(1 H -Imidazol-2-yl)pyridine, or 2-(2-pyridyl)benzimidazole as the P L ; the A L is resolved diaminocyclohexane. Precursor [Pt(P L )(Cl) 2 ] complexes were also characterized for comparison. While the cytotoxicity and DNA binding properties of the three precursors were unexceptional, the corresponding [Pt(P L )(A L )] 2+ complexes were promising; they exhibited different DNA binding interactions compared with Cisplatin but with similar, if not slightly better, cytotoxicity results. Complexes with 2-pyrrolidin-2-ylpyridine or 2-(2-pyridyl)benzimidazole ligands had similar DNA binding properties to those with 2-(1 H -Imidazol-2-yl)pyridine ligands but were not as cytotoxic to all cell lines. The variation in activity between cell lines was remarkable and resulted in significant selectivity indices in MCF10A and MCF-7 breast cancer cell lines, compared with previously described similar Pt(II) complexes such as 56MESS.

Cancer poses a significant threat to global health and new treatments are required to improve the prognosis for patients. Previously, unconventional platinum complexes designed to incorporate polypyridyl ligands paired with diaminocyclohexane have demonstrated anticancer activity in KRAS mutated cells, previously thought to be undruggable and have cytotoxicity values up to 100 times better than cisplatin. In this work, these complexes were used as inspiration to design six novel cyclometallated examples, whose fluorescence could be exploited to better understand the mechanism of action of these kinds of platinum drugs. The cytotoxicity results revealed that these cyclometallated complexes (CMCs) have significantly different activity compared to the complexes that inspired them; they are as cytotoxic as cisplatin and have much higher selectivity indices in breast cancer cell lines (MCF10A/MCF-7). Complexes 1b , 2a , and 3b all had very high selectivity indexes compared to previous Pt(II) complexes. This prompted further investigation into their DNA binding properties, which revealed that they had good affinity to ctDNA, especially CMCs 1a and 3b . Their inherent fluorescence was successfully utilised in the calculation of their DNA binding affinity and could be useful in future work.

A novel platinum(II) complex 47OMESS(II) and its platinum(IV) derivative 47OMESS(IV) were synthesized and characterized. Cytotoxicity studies against mesenchymal cells (MCs) and lung (A549), breast (MDA-MB-231), and melanoma (A375) cancer cells demonstrated 7-20-fold superior activity for both complexes relative to cisplatin. Remarkably, 47OMESS(IV) demonstrated 17-22-fold greater selectivity toward the cancerous cells compared to the non-cancerous MCs. Western blot analysis on A549 cells showed the involvement of the intrinsic apoptotic pathway. Cellular fractionation and uptake experiments in A549 cells using ICP-mass spectrometry (MS) indicated that 47OMESS(II) and 47OMESS(IV) cross the cellular membrane predominantly via active transport mechanisms. The significant improvement in selectivity that is exhibited by 47OMESS(IV) is reported for the first time for this class of complexes.

A new series of cytotoxic platinum(IV) complexes ( 1 - 8 ) incorporating halogenated phenylacetic acid derivatives (4-chlorophenylacetic acid, 4-fluorophenylacetic acid, 4-bromophenylacetic acid and 4-iodophenylacetic acid) were synthesised and characterised using spectroscopic and spectrometric techniques. Complexes 1 - 8 were assessed on a panel of cell lines including HT29 colon, U87 glioblastoma, MCF-7 breast, A2780 ovarian, H460 lung, A431 skin, Du145 prostate, BE2-C neuroblastoma, SJ-G2 glioblastoma, MIA pancreas, the ADDP-resistant ovarian variant, and the non-tumour-derived MCF10A breast line. The in vitro cytotoxicity results confirmed the superior biological activity of the studied complexes, especially those containing 4-fluorophenylacetic acid and 4-bromophenylacetic acid ligands, namely 4 and 6 , eliciting an average GI 50 value of 20 nM over the range of cell lines tested. In the Du145 prostate cell line, 4 exhibited the highest degree of potency amongst the derivatives, displaying a GI 50 value of 0.7 nM, which makes it 1700-fold more potent than cisplatin (1200 nM) and nearly 7-fold more potent than our lead complex, 56ME SS (4.6 nM) in this cell line. Notably, in the ADDP-resistant ovarian variant cell line, 4 (6 nM) was found to be almost 4700-fold more potent than cisplatin. Reduction reaction experiments were also undertaken, along with studies aimed at determining the complexes' solubility, stability, lipophilicity, and reactive oxygen species production.

The DNA-alkylating derivative chlorambucil was coordinated in the axial position to atypical cytotoxic, heterocyclic, and non-DNA coordinating platinum(IV) complexes of type, [Pt IV (H L )(A L )(OH) 2 ](NO 3 ) 2 (where H L is 1,10-phenanthroline, 5-methyl-1,10-phenanthroline or 5,6-dimethyl-1,10-phenanthroline, A L is 1 S ,2 S -diaminocyclohexane). The resultant platinum(IV)-chlorambucil prodrugs, PCLB , 5CLB , and 56CLB , were characterized using high-performance liquid chromatography, nuclear magnetic resonance, ultraviolet-visible, circular dichroism spectroscopy, and electrospray ionization mass spectrometry. The prodrugs displayed remarkable antitumor potential across multiple human cancer cell lines compared to chlorambucil, cisplatin, oxaliplatin, and carboplatin, as well as their platinum(II) precursors, PHEN SS , 5ME SS , and 56ME SS . Notably, 56CLB was exceptionally potent in HT29 colon, Du145 prostate, MCF10A breast, MIA pancreas, H460 lung, A2780, and ADDP ovarian cell lines, with GI 50 values ranging between 2.7 and 21 nM. Moreover, significant production of reactive oxygen species was detected in HT29 cells after treatment with PCLB , 5CLB , and 56CLB up to 72 h compared to chlorambucil and the platinum(II) and (IV) precursors.

Herein is described the development of a series of novel quadruplex DNA (QDNA)-stabilising cyclometallated square-planar metal complexes (CMCs). Melting experiments using quadruplex DNA (QDNA) demonstrated that interactions with the complexes increased the melting temperature by up to 19 °C. This QDNA stabilisation was determined in two of the major G-quadruplex structures formed in the human c-MYC promoter gene (c-MYC) and a human telomeric repeat sequence (H-Telo). The CMCs were found to stabilise H-telo more strongly than c-MYC, and the CMCs with the highest cytotoxic effect had a low-moderate correlation between H-telo binding capacity and cytotoxicity (R 2 values up to 10 times those of c-MYC). The melting experiments further revealed that the stabilisation effect was altered depending on whether the CMC was introduced before or after the formation of QDNA. All CMCs' GI 50 values were comparable or better than cisplatin in human cancer cell lines HT29, U87, MCF-7, H460, A431, Du145, BE2-C, SJ-G2, MIA, and ADDP. Complexes 6 , 7, and 9 were significantly more cytotoxic than cisplatin in all cell lines tested and had good to moderate selectivity indices, 1.7-4.5 in MCF10A/MCF-7. The emission quantum yields were determined to be relatively high (up to 0.064), and emission occurred outside cellular autofluorescence, meaning CMC fluorescence is ideal for in vitro analyses.

Virtual screening identified N-(6-((4-bromobenzyl)amino)hexyl)-3,5-bis(trifluoromethyl)benzenesulfonamide (1) a lead compound that bound to the S100A2-p53 binding groove. S100A2 is a Ca 2+ binding protein with implications in cell signaling and is known to be upregulated in pancreatic cancer. It is a validated pancreatic cancer drug target. Lead 1, inhibited the growth of the MiaPaCa-2 pancreatic cancer cell line (GI 50  = 2.97 μM). Focused compound libraries were developed to explore the SAR of this compound class with 4 libraries and 43 compounds total. Focused library (Library 1) development identified lipophillic sulfonamides as preferred for MiaPaCa-2 activity, with -CF 3 and -C(CH 3 ) 3 substituents well tolerated (MiaPaCa-2 GI 50  < 6 μM). Contraction of the hexylamino spacer to ethyl (Library 2) and propyl (Library 3) proved beneficial to activity against a broad spectrum panel of cancer cell lines: HT29 (lung), MCF-7 (breast), A2780 (ovarian), H460 (colon), A431 (skin), Du145 (prostate), BE2-C (neuroblastoma), U87 and SJ-G2 (glioblastoma) (cohort-1); and a pancreatic cancer cell line panel: MiaPaCa-2, BxPC-3, AsPC-1, Capan-2, HPAC and PANC-1 (cohort-2). With a marked preference for a propyl linker the observed GI 50 values ranged from 1.4 to 30 μM against cohort-1 and 1.4-30 μM against cohort-2 cell lines. In Library 4 the terminal aromatic moiety was explored with 4-substituted analogues preferred (with activity of 48 (4-Cl) > 47 (3-Cl) > 46 (2-Cl)) against the cell lines examined. The introduction of bulky aromatic moieties was well tolerated, e.g. dihydrobenzo[b][1,4]dioxine (51) returned cohort-2 GI 50 values of 1.2-3.4 μM. In all instances the observed docked binding poses and binding scores were consistent with the observed cytotoxicity. This in turn supports, but does not prove, that these analogues function via S100A2-p53 binding groove inhibition., (Crown Copyright © 2022. Published by Elsevier Ltd. All rights reserved.)

Five focused libraries of pyrimidine-based dynamin GTPase inhibitors, in total 69 compounds were synthesised, and their dynamin inhibition and broad-spectrum cytotoxicity examined. Dynamin plays a crucial role in mitosis, and as such inhibition of dynamin was expected to broadly correlate with the observed cytotoxicity. The pyrimidines synthesised ranged from mono-substituted to trisubstituted. The highest levels of dynamin inhibition were noted with di- and tri- substituted pyrimidines, especially those with pendent amino alkyl chains. Short chains and simple heterocyclic rings reduced dynamin activity. There were three levels of dynamin activity noted: 1-10, 10-25 and 25-60 μM. Screening of these compounds in a panel of cancer cell lines: SW480 (colon), HT29 (colon), SMA (spontaneous murine astrocytoma), MCF-7 (breast), BE2-C (glioblastoma), SJ-G2 (neuroblastoma), MIA (pancreas), A2780 (ovarian), A431 (skin), H460 (lung), U87 (glioblastoma) and DU145 (prostate) cell lines reveal a good correlation between the observed dynamin inhibition and the observed cytotoxicity. The most active analogues (31 a,b) developed returned average GI 50 values of 1.0 and 0.78 μM across the twelve cell lines examined. These active analogues were: N 2 -(3-dimethylaminopropyl)-N 4 -dodecyl-6-methylpyrimidine-2,4-diamine (31 a) and N 4 -(3-dimethylaminopropyl)-N 2 -dodecyl-6-methylpyrimidine-2,4-diamine (31 b)., (© 2021 Wiley-VCH GmbH.)

In silico screening predicted 1 (N-(4-((4-(3-(4-(3-methoxyphenyl)-1H-1,2,3-triazol-1-yl)propyl)piperazin-1-yl) sulfonyl)-phenyl)acetamide) as an inhibitor of the S100A2-p53 protein-protein interaction. S100A2 is a validated pancreatic cancer drug target. In the MiaPaCa-2 pancreatic cell line, 1 was a ∼50 μM growth inhibitor. Synthesis of five focused compound libraries and cytotoxicity screening revealed increased activity from the presence of electron withdrawing moieties on the sulfonamide aromatic ring, with the 3,5-bis-CF 3 Library 3 analogues the most active, with GI 50 values of 0.91 (3-ClPh; 13 i; BxPC-3, Pancreas) to 9.0 μM (4-CH 3 ; 13 d; PANC-1, Pancreas). Activity was retained against an expanded pancreatic cancer cell line panel (MiaPaCa-2, BxPC-3, AsPC-1, Capan-2, PANC-1 and HPAC) and the normal cell line MCF10A (breast). Bulky 4-disposed substituents on the terminal phenyl ring enhanced broad spectrum activity with growth inhibition values spanning 1.1 to 3.1 μM (4-C(CH 3 ) 3 ; 13 e; BxPC-3 and AsPC-1 (pancreas), respectively). Central alkyl spacer contraction from propyl to ethyl proved detrimental to activity with Library 4 and 5.5- to 10-fold less cytotoxic than the propyl linked Library 2 and Library 3. The data herein was consistent with the predicted binding poses of the compounds evaluated. The highest levels of cytotoxicity were observed with those analogues best capable of adopting a near identical pose to the p53-peptide in the S100A2-p53 binding groove., (© 2021 Wiley-VCH GmbH.)

In silico approaches identified 1, N-(6-((4-bromo- benzyl)amino)hexyl)-3,5-bis(trifluoromethyl)benzene sulfonamide, as a potential inhibitor of the S100A2-p53 protein-protein interaction, a validated pancreatic cancer drug target. Subsequent cytotoxicity screening revealed it to be a 2.97 μM cell growth inhibitor of the MiaPaCa-2 pancreatic cell line. This is in keeping with our hypothesis that inhibiting this interaction would have an anti-pancreatic cancer effect with S100A2, the validated PC drug target. A combination of focused library synthesis (three libraries, 24 compounds total) and cytotoxicity screening identified a propyl alkyl diamine spacer as optimal; the nature of the terminal phenyl substituent had limited impact on observed cytotoxicity, whereas N-methylation was detrimental to activity. In total 15 human cancer cell lines were examined, with most analogues showing broad-spectrum activity. Near uniform activity was observed against a panel of six pancreatic cancer cell lines: MiaPaCa-2, BxPC-3, AsPC-1, Capan-2, HPAC and PANC-1. In all cases there was good to excellent correlation between the predicted docking pose in the S100A2-p53 binding groove and the observed cytotoxicity, especially in the pancreatic cancer cell line with high endogenous S100A2 expression. This supports S100A2 as a pancreatic cancer drug target., (© 2021 Wiley-VCH GmbH.)

To exploit the interaction of the aryl hydrocarbon receptor (AhR) pathway in developing breast-cancer-specific cytotoxic compounds, we examined the breast cancer selectivity and the docking pose of the AhR ligands (Z)-2-(2-aminophenyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (NAP-6; 5) and 10-chloro-7H-benzo[de]benzo[4,5]imidazo[2,1-a]isoquinolin-7-one (10-Cl-BBQ; 6). While the breast cancer selectivity of 5 in vitro is known, we discuss the SAR around this lead and, by using phenotypic cell-line screening and the MTT assay, show for the first time that 6 also presents with breast cancer selectivity, notably in the triple-negative (TN) receptor breast cancer cell line MDA-MB-468, the ER+ breast cancer cell lines T47D, ZR-75-1 and the HER2+ breast cancer cell line SKBR3 (GI 50 values of 0.098, 0.97, 0.13 and 0.21 μM, respectively). Indeed, 6 is 55 times more potent in MDA-MB-468 cells than normal MCF10A breast cells (GI 50 of 0.098 vs 5.4 μM) and more than 130 times more potent than in cell lines derived from pancreas, brain and prostate (GI 50 of 0.098 vs 10-13 μM). Molecular docking poses of 5 and 6 together with analogue synthesis and phenotypic screening show the importance of the naphthalene moiety, and an ortho-disposed substituent on the N-phenyl moiety for biological activity., (© 2020 Wiley-VCH GmbH.)

Lead (Z)-N-(4-(2-cyano-2-(3,4-dichlorophenyl)vinyl)phenyl)acetamide, 1 showed MCF-7 GI 50 =30 nM and 400-fold selective c.f. MCF10A (normal breast tissue). Acetamide moiety modification (13 a-g) to introduce additional hydrophobicity was favoured with MCF-7 breast cancer cell activity enhanced at 1.3 nM. Other analogues were potent against the HT29 colon cancer cell line at 23 nM. Textbook SAR data was observed in the MCF-7 cell line, in an MTT assay, via the ortho (17 a), meta (17 b) and para (13 f). The amino alcohol -OH moiety was pivotal, but no stereochemical preference noted. But, these data did not fit our homology modelling expectations. Aberrant MTT ((3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) screening results and metabolic interference confirmed by sulforhodamine B (SRB) screening. Interfering analogues resulted in 120 and 80-fold CYP1A1 and CYP1A2 amplification, with no upregulation of SULT1A1. This is consistent with activation of the AhR pathway. Piperidine per-deuteration reduced metabolic inactivation. 3-OH / 4-OH piperidine analogues showed differential MTT and SRB activity supporting MTT assay metabolic inactivation. Data supports piperidine 3-OH, but not the 4-OH, as a CYP substrate. This family of β-amino alcohol substituted 3,4-dichlorophenylacetonitriles show broad activity modulated via the AhR pathway. By SRB analysis the most potent analogue was 23 b, (Z)-3-(4-(3-(4-phenylpiperidin-1-yl)-2-hydroxypropoxy)phenyl)-2-(3,4-dichlorophenyl)-acrylonitrile., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Lipophilic platinum(iv) complexes were synthesised of the type [Pt(HL)(AL)(OH)(R)]2+ and [Pt(HL)(AL)(R)2]2+ (HL = 5,6-dimethyl-1,10-phenanthroline or 1,10-phenanthroline; AL = 1S,2S-diaminocyclohexane and R = increasingly lipophilic carboxylate axial ligands (C10-18)) from hydrophilic platinum(ii) precursors that exhibit exceptional anticancer activity. The increased overall lipophilicity of the complexes suggested the formation of spontaneously self-assembled structures in an aqueous environment. The anti-proliferative properties were assessed against one non-cancerous and a panel of cancerous cell lines. Nanomolar levels of activity were observed against several cell lines, with the lowest GI50 of 3.4 nm against the Du145 prostate cancer cell line and over 1100-fold greater activity than cisplatin against HT29 colon carcinoma. RP-HPLC was utilised to establish the relative lipophilicities of each complex. While there seemed to be an increase in cellular accumulation for the lipophilic derivatives in some instances, ICP-MS studies showed no clear correlation between increasing lipophilicity, cellular accumulation and cytotoxicity.

Novel platinum(iv) complexes were synthesised to examine the facile modulation of the lipophilicity of the complex by incorporating axial ligands of increasing length, ranging from 2-6 carbons. RP-HPLC was used to establish the lipophilicity of each complex. The in vitro cytotoxicities of all complexes were determined against a panel of malignant cell lines and a non-cancerous cell line. While there was no clear correlation between lipophilicity and cytotoxicity, all complexes demonstrated nanomolar activity against all cell lines. The most potent complexes exhibited 850-fold greater activity than cisplatin against HT29 colon carcinoma with GI50 values of 13 nM.

Octahydroepoxyisoindole analogues of norcantharidin were accessed through a Diels-Alder reaction of an amine-substituted furan with maleic anhydride and subsequent reduction of the bicyclo[2.2.1]heptene olefin. Despite retention of the carboxylate and the ether bridgehead known to impart cytotoxic activity to norcantharidin, none of these analogues displayed notable cytotoxicity against the 11 cell lines examined: HT29 (colon), MCF-7 (breast), A2780 (ovarian), H460 (lung), A431 (skin), Du145 (prostate), BE2-C (neuroblastoma), SJ-G2 and U87 (glioblastoma), MIA (pancreatic), and SMA (spontaneous murine astrocytoma). The incorporation of an amino-substituted system post-synthesis of norcantharidin afforded facile access to 14 acid/amide-substituted norcantharidin analogues. Of these, only four displayed sufficient activity at the initial 25 μm compound screening dose to warrant full evaluation of growth inhibition. Common to these analogues was the presence of a 4-biphenyl moiety, and in particular 3-(2-(furan-2-ylmethyl)-3-(4-biphenylamino)-3-oxopropylcarbamoyl)-7-oxabicyclo[2.2.1]heptane-2-carboxylic acid (13 c) and 3-(2-(pyrrole-2-ylmethyl)-3-(4-biphenylamino)-3-oxopropylcarbamoyl)-7-oxabicyclo[2.2.1]heptane-2-carboxylic acid (24) displayed high levels of cytotoxicity, returning GI 50 values of 15 nm (HT29) to 2.9 μm (U87) and 17 nm (SMA) to 2.8 μm (U87), respectively. These are the most cytotoxic norcantharidin analogues reported to date., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Knoevenagel condensation of 3,4-dichloro- and 2,6-dichlorophenylacetonitriles gave a library of dichlorophenylacrylonitriles. Our leads (Z)-2-(3,4-dichlorophenyl)-3-(1H-pyrrol-2-yl)acrylonitrile (5) and (Z)-2-(3,4-dichlorophenyl)-3-(4-nitrophenyl)acrylonitrile (6) displayed 0.56±0.03 and 0.127±0.04 μm growth inhibition (GI 50 ) and 260-fold selectivity for the MCF-7 breast cancer cell line. A 2,6-dichlorophenyl moiety saw a 10-fold decrease in potency; additional nitrogen moieties (-NO 2 ) enhanced activity (Z)-2-(2,6-dichloro-3-nitrophenyl)-3-(2-nitrophenyl)acrylonitrile (26) and (Z)-2-(2,6-dichloro-3-nitrophenyl)-3-(3-nitrophenyl)acrylonitrile (27), with the corresponding -NH 2 analogues (Z)-2-(3-amino-2,6-dichlorophenyl)-3-(2-aminophenyl)acrylonitrile (29) and (Z)-2-(3-amino-2,6-dichlorophenyl)-3-(3-aminophenyl)acrylonitrile (30) being more potent. Despite this, both 29 (2.8±0.03 μm) and 30 (2.8±0.03 μm) were found to be 10-fold less cytotoxic than 6. A bromine moiety effected a 3-fold enhancement in solubility with (Z)-3-(5-bromo-1H-pyrrol-2-yl)-2-(3,4-dichlorophenyl)acrylonitrile 18 relative to 5 at 211 μg mL -1 . Modeling-guided synthesis saw the introduction of 4-aminophenyl substituents (Z)-3-(4-aminophenyl)-2-(3,4-dichlorophenyl)acrylonitrile (35) and (Z)-N-(4-(2-cyano-2-(3,4-dichlorophenyl)vinyl)phenyl)acetamide (38), with respective GI 50 values of 0.030±0.014 and 0.034±0.01 μm. Other analogues such as 35 and 36 were found to have sub-micromolar potency against our panel of cancer cell lines (HT29, colon; U87 and SJ-G2, glioblastoma; A2780, ovarian; H460, lung; A431, skin; Du145, prostate; BE2-C, neuroblastoma; MIA, pancreas; and SMA, murine glioblastoma), except compound 38 against the U87 cell line. A more extensive evaluation of 38 ((Z)-N-(4-(2-cyano-2-(3,4-dichlorophenyl)vinyl)phenyl)acetamide) in a panel of drug-resistant breast carcinoma cell lines showed 10-206 nm potency against MDAMB468, T47D, ZR-75-1, SKBR3, and BT474. Molecular Operating Environment docking scores showed a good correlation between predicted binding efficiencies and observed MCF-7 cytotoxicity. This supports the use of this model in the development of breast-cancer-specific drugs., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Platinum complexes of the type [Pt(P L )(A L )] 2+ where P L is a derivative of 1,10-phenanthroline and A L is cis-1,4-diaminocyclohexane (1,4-dach), have been synthesised and characterised by ultraviolet spectroscopy, elemental microanalysis, nuclear magnetic resonance and X-ray crystallography. The calf-thymus DNA binding affinity of these complexes was determined by isothermal titration calorimetry, revealing higher DNA affinity than their 1S,2S-diaminocyclohexane analogues. In vitro cytotoxicity was assessed in eleven human cell lines, revealing unexpectedly low activity for the 1,4-dach complexes.

We have previously reported the synthesis and breast cancer selectivity of ( Z )-2-(3,4-dichlorophenyl)-3-(1 H -pyrrol-2-yl)acrylonitrile (ANI-7) in cancer cell lines. To further evaluate the selectivity of ANI-7, we have expanded upon the initial cell line panel to now include the breast cancer cell lines (MCF7, MCF7/VP16, BT474, T47D, ZR-75-1, SKBR3, MDA-MB-468, BT20, MDA-MB-231); normal breast cells (MCF-10A); and cell lines derived from colon (HT29), ovarian (A2780), lung (H460), skin (A431), neuronal (BE2C), glial (U87, SJG2), and pancreatic (MIA) cancers. We now show that ANI-7 is up to 263-fold more potent at inhibiting the growth of breast cancer cell lines (MCF7, MCF7/VP16, BT474, T47D, ZR-75-1, SKBR3, MDA-MB-468) than normal breast cells (MCF-10A) or cell lines derived from other tumor types. Measures of growth inhibition, cell cycle analysis, morphologic assessment, Western blotting, receptor binding, gene expression, small interfering RNA technology, reporter activity, and enzyme inhibition assays were exploited to define the mechanism of action of ANI-7. In this work, we report that ANI-7 mediates its effects via the activation of the aryl hydrocarbon receptor (AhR) pathway and the subsequent induction of CYP1-metabolizing mono-oxygenases. The metabolic conversion of ANI-7 induces DNA damage, checkpoint activation, S-phase cell cycle arrest, and cell death in sensitive breast cancer cell lines. Basal expression of AhR, the AhR nuclear translocator, and the CYP1 family members do not predict for sensitivity; however, inherent expression of the phase II-metabolizing enzyme sulfur transferase 1A1 does. For the first time, we identify ( Z )-2-(3,4-dichlorophenyl)-3-(1 H -pyrrol-2-yl)acrylonitrile as a new AhR ligand., (Copyright © 2018 by The American Society for Pharmacology and Experimental Therapeutics.)

In spite of the recent advancements in oncology, the overall survival rate for pancreatic cancer has not improved over the last five decades. Eucalypts have been linked with cytotoxic and anticancer properties in various studies; however, there is very little scientific evidence that supports the direct role of eucalypts in the treatment of pancreatic cancer. This study assessed the anticancer properties of aqueous and ethanolic extracts of four Eucalyptus species using an MTT assay. The most promising extracts were further evaluated using a CCK-8 assay. Apoptotic studies were performed using a caspase 3/7 assay in MIA PaCa-2 cells. The aqueous extract of Eucalyptus microcorys leaf and the ethanolic extract of Eucalyptus microcorys fruit inhibited the growth of glioblastoma, neuroblastoma, lung and pancreatic cancer cells by more than 80% at 100 μg/mL. The E. microcorys and Eucalyptus saligna extracts showed lower GI 50 values than the ethanolic Eucalyptus robusta extract in MIA PaCa-2 cells. Aqueous E. microcorys leaf and fruit extracts at 100 μg/mL exerted significantly higher cell growth inhibition in MIA PaCa-2 cells than other extracts (p < 0.05). Statistically similar IC 50 values (p > 0.05) were observed in aqueous E. microcorys leaf (86.05 ± 4.75 μg/mL) and fruit (64.66 ± 15.97 μg/mL) and ethanolic E. microcorys leaf (79.30 ± 29.45 μg/mL) extracts in MIA PaCa-2 cells using the CCK-8 assay. Caspase 3/7-mediated apoptosis and morphological changes of cells were also witnessed in MIA PaCa-2 cells after 24 h of treatment with the extracts. This study highlighted the significance of E. microcorys as an important source of phytochemicals with efficacy against pancreatic cancer cells. Further studies are warranted to purify and structurally identify individual compounds and elucidate their mechanisms of action for the development of more potent and specific chemotherapeutic agents for pancreatic cancer.

Xao tam phan (Paramignya trimera) has been used for the treatment of cancer and cancer-like aliments. Among different parts of the P. trimera plant, leaf is considered as a residual part after harvesting of the root. This study aimed to determine the physiochemical properties and the antioxidant and anti-proliferative capacities of P. trimera leaf (PTL) using microwave drying for the preparation of dry sample; MeOH and microwave-assisted extraction for the preparation of crude extract; and freeze-drying for the preparation of powdered extract. The results showed that total phenolic, total flavonoid, proanthocyanidin, and saponin contents of PTL prepared by microwave drying at 450 W were 25.4 mg gallic acid equiv. (GAE), 86.3 mg rutin equiv. (RE), 5.6 mg catechin equiv. (CE), and 702.1 mg escin equiv. (EE) per gram dried sample, respectively. Gallic acid, protocatechuic acid, ellagic acid, rutin, and quercetin were identified in the PTL MeOH extract. Dried PTL displayed potent antioxidant activity, while the powdered PTL extract exhibited great anti-proliferative capacity on various cancer cell lines including MiaPaCa-2 (pancreas), HT29 (colon), A2780 (ovarian), H460 (lung), A431 (skin), Du145 (prostate), BE2-C (neuroblastoma), MCF-7 (breast), MCF-10A (normal breast), and U87, SJ-G2, and SMA (glioblastoma). Anti-proliferative capacity on pancreatic cancer cells (MiaCaPa2, BxPc3, and CFPAC1) of PTL extract (200 μg/ml) was significantly higher (P < 0.05) than those of ostruthin (20 μg/ml) and gemcitabine (50 nm), and to be comparable to the powdered P. trimera root extract and a saponin-enriched extract from quillajia bark (a commercial product). The findings from this study allow us to conclude that the PTL is a rich source of phytochemicals that possess promising antioxidant and anti-proliferative activities, therefore it shows potential as lead compounds for application in the nutraceutical, medicinal and pharmaceutical industries., (© 2017 Wiley-VHCA AG, Zurich, Switzerland.)

A series of 28 norcantharidin (NorC)-inspired analogues were accessed via a robust two-step Ugi intramolecular Diels-Alder (IMDA) sequence. Four analogues displayed whole-cell cytotoxicity equipotent to that of NorC and cisplatin against a number of cancer cell lines and a normal breast cell line (MCF10A). Notably, (3S,3aS,6R)-2-benzyl-7-methyl-N-(naphthalen-2-yl)-1-oxo-1,2,3,6-tetrahydro-3a,6-epoxyisoindole-3-carboxamide (trans-27) displayed superior whole-cell activity against breast (MCF-7, GI 50 =2.9 μm) and colon (HT29, GI 50 =6.4 μm) cancer cell lines relative to the control (cisplatin), which elicited respective GI 50 values of 6.5 and 11.3 μm against the aforementioned cell lines. This analogue also displayed improved activity relative to NorC across the breast (MCF-7, GI 50 =2.9 μm; NorC GI 50 =7.5 μm), ovarian (A2780, GI 50 =2.2 μm; NorC GI 50 =4.4 μm), and neuroblastoma (BE2-C, GI 50 =2.2 μm; NorC GI 50 =3.7 μm) cancer cell lines. Structure-activity relationship (SAR) investigations demonstrated that retention of sp 2 hybridized connections within the tetrahydroepoxyisoindole carboxamide scaffold is crucial, as aromatization to a phenolic functionality decreased activity, whereas removal of a single olefin bond abolished cytotoxicity. Nonetheless, with respect to the latter, use of crotonic acid as opposed 2-butynoic acid in the Ugi-IMDA sequence imparted a significant improvement to diastereoselectivity, with the cis/trans isomer ratio shifting from ≈1:1.2 to ≈0.5:9.5., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We describe a simple flow chemistry approach to libraries of ethyl 3-oxo-2-(substituted-phenylamino)-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carboxylates (12a-l) and N-ethyl-3-oxo-2-(substituted-phenylamino)-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carboxamides (13a-l) in 38-87% yields. This scaffold is poorly described in the chemical literature. Screening against a panel of 11 cancer and one normal cell line showed that the amide linked library 13a-l was devoid of toxicity. Whereas the ester linked analogues 12b, 12c, 12g, 12j and 12l were highly cytotoxic with growth inhibition (GI 50 ) values from 0.34 to >50 μM across all cell lines, with the 2-OH-Ph substituted 12l analogue presenting with sub-micromolar potency against the A2780 (ovarian; 0.34 ± 0.04 μM), BEC-2 (glioblastoma; 0.35 ± 0.06 μM), MIA (pancreas; 0.91 ± 0.054 μM) and SMA (murine glioblastoma; 0.77 ± 0.029 μM) carcinoma cell lines. Interestingly, the U87 glioblastoma cell line showed inherent resistance to growth inhibition by all analogues (GI 50 32 to >50 μM) while the A2780 cells were highly sensitive (GI 50 3.8-0.34 μM), suggesting that the analogues developed herein may be valuable lead compounds for the development of ovarian carcinoma specific cytotoxic agents. The differences in amide versus ester cytotoxicity was consitent with esterase cleaveage to release the cytotoxic warhead.

A series of quinolone-2-(1H)-ones derived from the Ugi-Knoevenagel three- and four-component reaction were prepared exhibiting low micromolar cytotoxicity against a panel of eight human cancer cell lines known to possess the Hedgehog Signalling Pathway (HSP) components, as well as the seminoma TCAM-2 cell line. A focused SAR study was conducted and revealed core characteristics of the quinolone-2-(1H)-ones required for cytotoxicity. These requirements included a C3-tethered indole moiety, an indole C5-methyl moiety, an aliphatic tail or an ester, as well as an additional aromatic moiety. Further investigation in the SAG-activated Shh-LIGHT2 cell line with the most active analogues: 2-(3-cyano-2-oxo-4-phenylquinolin-1(2H)-yl)-2-(1-methyl-1H-indol-3-yl)-N-(pentan-2-yl)acetamide (5), 2-(3-cyano-2-oxo-4-phenylquinolin-1(2H)-yl)-2-(5-methyl-1H-indol-3-yl)-N-(pentan-2-yl)acetamide (23) and ethyl (2-(3-cyano-2-oxo-4-phenylquinolin-1(2H)-yl)-2-(5-methyl-1H-indol-3-yl)acetyl)glycinate (24) demonstrated a down regulation of the HSP via a reduction in Gli expression, and in the mRNA levels of Ptch1 and Gli2. Analogues 5, 23 and 24 returned in cell inhibition values of 11.6, 2.9 and 3.1 μM, respectively, making this new HSP-inhibitor pharmacophore amongst the most potent non-Smo targeted inhibitors thus far reported.

This study reports a detailed biophysical analysis of the DNA binding and cytotoxicity of six platinum complexes (PCs). They are of the type [Pt(PL )(SS-dach)]Cl2 , where PL is a polyaromatic ligand and SS-dach is 1S,2S-diaminocyclohexane. The DNA binding of these complexes was investigated using six techniques including ultraviolet and fluorescence spectroscopy, linear dichroism, synchrotron radiation circular dichroism, isothermal titration calorimetry and mass spectrometry. This portfolio of techniques has not been extensively used to study the interactions of such complexes previously; each assay provided unique insight. The in vitro cytotoxicity of these compounds was studied in ten cell lines and compared to the effects of their R,R enantiomers; activity was very high in Du145 and SJ-G2 cells, with some submicromolar IC50 values. In terms of both DNA affinity and cytotoxicity, complexes of 5,6-dimethyl-1,10-phenanthroline and 2,2'-bipyridine exhibited the greatest and least activity, respectively, suggesting that there is some correlation between DNA binding and cytotoxicity., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We have developed six dihydroxidoplatinum(IV) compounds with cytotoxic potential. Each derived from active platinum(II) species, these complexes consist of a heterocyclic ligand (HL) and ancillary ligand (AL) in the form [Pt(HL)(AL)(OH)2](2+), where HL is a methyl-functionalised variant of 1,10-phenanthroline and AL is the S,S or R,R isomer of 1,2-diaminocyclohexane. NMR characterisation and X-ray diffraction studies clearly confirmed the coordination geometry of the octahedral platinum(IV) complexes. The self-stacking of these complexes was determined using pulsed gradient stimulated echo nuclear magnetic resonance. The self-association behaviour of square planar platinum(II) complexes is largely dependent on concentration, whereas platinum(IV) complexes do not aggregate under the same conditions, possibly due to the presence of axial ligands. The cytotoxicity of the most active complex, exhibited in several cell lines, has been retained in the platinum(IV) form., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

An efficient and divergent methodology for the synthesis of new anthracenone-pyranones and anthracenone-furans is described. Key reactions discussed in these syntheses include an aldehyde promoted annulation with a β-keto-sulfoxide, a domino alkyne insertion/carbonylation/Nu-acylation and a DMEDA promoted Castro-Stephens reaction. We also report the in vitro growth inhibition of these compounds in a range of human cancer cells. The natural product BE-26554A displayed good cell growth activity on BE2-C neuroblastoma and SMA glioblastoma cell lines at 0.17 and 0.16μM (GI50), respectively. Of note, were a CF3 functionalised anthracenone 4-pyranone (chromone) derivative 22, and an anthracenone-furan derivative 54 which displayed 0.20μM and 0.38μM growth inhibition, respectively, in the BE2-C neuroblastoma cell line., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Drugs that inhibit DNA topoisomerase I and DNA topoisomerase II have been widely used in cancer chemotherapy. We report herein the results of a focused medicinal chemistry effort around novel ellipticinium salts which target topoisomerase I and II enzymes with improved solubility. The salts were prepared by reaction of ellipticine with the required alkyl halide and evaluated for DNA intercalation, topoisomerase inhibition and growth inhibition against 12 cancer cell lines. Results from the topoisomerase I relaxation assay indicated that all novel ellipticine derivatives behaved as intercalating agents. At a concentration of 100 μM, specific topoisomerase I inhibition was not observed. Two of the derivatives under investigation were found to fully inhibit the DNA decatenation reaction at a concentration of 100 μM, indicative of topoisomerase II inhibition. N-Alkylation of ellipticine was found to enhance the observed growth inhibition across all cell lines and induce growth inhibition comparable to that of Irinotecan (CPT-11; GI(50) 1-18 μM) and in some cell lines better than Etoposide (VP-16; GI(50) = 0.04-5.2 μM). 6-Methylellipticine was the most potent growth inhibitory compound assessed (GI(50) = 0.47-0.9 μM). N-Alkylation of 6-methylellipticine was found to reduce this response with GI(50) values in the range of 1.3-28 μM.

With our lead compound (E)-3-(4-chlorophenyl)-2-(1H-pyrrole-2-carbonyl)acrylonitrile (1) inducing 50% growth inhibition of 11 cancer cell lines at 27-61 μM, potency enhancements were rapidly established through the synthesis of a series of focused compound libraries. Six highly focused libraries (46 compounds in total) were synthesised. Each library allowed the identification of a new lead compound, viz Library A identified (E)-3-(pentafluorophenyl)-2-(1H-pyrrole-2-carbonyl)acrylonitrile (11) and (E)-3-(1H-indol-3-yl)-2-(1H-pyrrole-2-carbonyl)acrylonitrile (13) as inhibitors with improved cytotoxicity. Synthesis of discrete libraries of amidoacrylamide analogues (Ar-CC(CN)-Ar✠Ar-CC(CN)-C(O)NH)-Ar) resulted in a series of analogues significantly more potent that the lead, 1. Three furan three analogues: (E)-3-(5-chlorofuran-2-yl)-2-cyano-N-(4-methoxybenzyl)acrylamide (33), (E)-3-(5-bromofuran-2-yl)-2-cyano-N-(4-methoxybenzyl)acrylamide (34) and (E)-2-cyano-3-(furan-3-yl)-N-(4-methoxybenzyl)acrylamide (37) returned broad spectrum growth inhibition (GI(50) values of 5-16 μM). Replacement of the furan moiety with simple aromatics gave an additional three analogues: (E)-2-cyano-N-(4-methoxybenzyl)-3-phenylacrylamide (39), (E)-3-(4-chlorophenyl)-2-cyano-N-(4-methoxybenzyl)acrylamide (41) and (E)-2-cyano-N-(4-methoxyphenyl)-3-(naphthalen-1-yl)acrylamide (45) with GI(50) values of 7-24 μM. The final library retained the aromatic substituents but introduced a 3,4-dichlorbenzylamine moiety to afford the 1-naphthyl substituted 52, which was the most potent broad spectrum cytotoxic analogue produced here in with an average GI(50)=8.6 μM. This represents a fivefold potency enhancement relative to 1 and a new cytotoxic scaffold suitable for further development., (Copyright © 2012. Published by Elsevier Ltd.)

We previously reported the discovery of a simple conjugated cyano pharmacophore which had led to the development of (Z)-2-(3,4-dichlorophenyl)-3-(4-nitrophenyl)acrylonitrile, as a selective inhibitor of oestrogen receptor positive (ER+ve) human breast cancer cell line, MCF-7. Further exploration though modification of the acrylonitrile and aromatic substituents has highlighted key structural components necessary for broad spectrum cytotoxicity. The acrylic acid derivates (Z)-2-(3,4-dichlorophenyl)-3-(4-nitrophenyl)acrylic acid and (Z)-2-(3,4-dichlorophenyl)-3-(4-methoxyphenyl)acrylic acid (9) were inactive; confirming the importance of the cyanide moiety. The most potent 2-phenylacrylonitriles synthesized were (Z)-2-(3,4-dichlorophenyl)-3-(1H-indol-3-yl)acrylonitrile and (Z)-2-(3,4-dichlorophenyl)-3-(1H-indol-5-yl)acrylonitrile (20) with an average GI(50) values of 1.4 and 0.53 μM respectively. Five additional (Z)-2-(3,4-dichlorophenyl)-3-(indolyl)acrylonitriles also displayed average GI(50) values of ≤8.4 μM. In the case of indole, this represents a 32-fold increase in broad spectrum cytotoxicity relative to the lead., (Crown Copyright © 2012. Published by Elsevier Masson SAS. All rights reserved.)

Cantharidin (1) and norcantharidin (2) display high levels of anticancer activity against a broad range of tumour cell lines. Synthetic manipulation of norcantharidin yields (3S,3aR,4S,7R,7aS)-3-hydroxyhexahydro-4,7-epoxyisobenzofuran-1(3H)-one (3), which also displays a high level of anticancer activity against tumour cells but interestingly, shows selectivity towards HT29 (colon; GI(50) = 14 μM) and SJ-G2 (glioblastoma; GI(50) = 15 μM) cell lines. Substitution at the hydroxyl group of the cyclic lactone within (3) produces a diasteromeric pair of products that have no difference in cytotoxicity over the cell lines tested. Incorporation of an isopropyl tail at this position (16) produced the most promising compound of this series to date, with strong selectivity towards HT29 (colon; GI(50) = 19 μM) and SJ-G2 (glioblastoma; GI(50) = 21 μM) cell lines but completely void of any activity against the remaining tumour cell lines (GI(50) > 100 μM), as per the parent molecule. We also discovered that the introduction of a terminal phosphate moiety (28) at the same position produced a different trend in cytotoxicity with strong activity in BE2-C (neuroblastoma; GI(50) = 9 μM) cells; suggestive of an alternate mode of action., (Crown Copyright © 2012. Published by Elsevier Masson SAS. All rights reserved.)

A family of norcantharidin analogues possessing a terminal alcohol (ethanol, propanol, butanol, pentanol, hexanol and cyclohexanol) moiety were treated with either chlorodiethyl, chlorodiphenyl or chloro-bis-trichloroethyl-phosphate to afford highly focused libraries of the corresponding phosphate esters. Subsequent biological screening against a panel of nine human cancer cell lines identified a trend between the ease of phosphate unmasking (phosphate ester hydrolysis) and cell death. The most potent analogues possessed either a diphenyl or a bis-trichloroethyl moiety. The effect of alkyl spacer was also examined with the hexyl analogues typically more potent. 4-Aza-4-(3-{bis(2,2,2-trichloroethyl)phosphate}propyl)-10-oxatricyclo[5.2.1.0]decane-3,5-dione (10b) was the most potent analogue synthesised with an average GI(50) of 11 μM across a panel of nine human carcinoma cell lines: colon carcinoma (HT29 and SW480); breast carcinoma (MCF-7); ovarian carcinoma (A2780); lung carcinoma (H460); skin carcinoma (A431); prostate carcinoma (DU145); neuronal carcinoma (BE2-C) and brain carcinoma (SJ-G2). This represents a fivefold improvement in anti-proliferative activity relative to the lead, norcantharidin., (Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.)

Inhibitors of mitotic proteins such as Aurora kinase and polo-like kinase have shown promise in preclinical or early clinical development for cancer treatment. We have reported that the MiTMAB class of dynamin small molecule inhibitors are new antimitotic agents with a novel mechanism of action, blocking cytokinesis. Here, we examined 5 of the most potent of a new series of dynamin GTPase inhibitors called dynoles. They all induced cytokinesis failure at the point of abscission, consistent with inhibition of dynamin while not affecting other cell cycle stages. All 5 dynoles inhibited cell proliferation (MTT and colony formation assays) in 11 cancer cell lines. The most potent GTPase inhibitor, dynole 34-2, also induced apoptosis, as revealed by cell blebbing, DNA fragmentation, and PARP cleavage. Cell death was induced specifically following cytokinesis failure, suggesting that dynole 34-2 selectively targets dividing cells. Dividing HeLa cells were more sensitive to the antiproliferative properties of all 5 dynoles compared with nondividing cells, and nontumorigenic fibroblasts were less sensitive to cell death induced by dynole 34-2. Thus, the dynoles are a second class of dynamin GTPase inhibitors, with dynole 34-2 as the lead compound, that are novel antimitotic compounds acting specifically at the abscission stage.

Mitotane (o,p'-DDD or (1,1-dichloro-2-[o-chlorophenyl]-2-[p-chlorophenyl]ethane, DDD) is the drug of choice for non-resectable and metastatic adrenocortical carcinomas (ACC). Measurement of mitotane and metabolites, o,p'-DDE (1,1-dichloro-2-[p-chlorophenyl]-2-[o-chlorophenyl]ethene, DDE) and o,p'-DDA (1,1-[o,p'-dichlorodiphenyl] acetic acid, DDA) provides a better understanding of mitotane pharmacokinetics and pharmacodynamics. We have developed a simple, robust and efficient high performance liquid chromatography (HPLC) method to measure mitotane and its two main metabolites, DDE and DDA. The method involves a single ethanol extraction of mitotane, DDE, DDA, and an internal standard (int std) p,p'-DDD (1,1-dichloro-2,2-bis(p-chlorophenyl)ethane) with an extraction efficiency of 77-88%. All compounds are measured simultaneously using a reversed-phase phenyl HPLC column with an isocratic elution of mobile phase at a flow rate of 0.6 ml/min followed by UV detection at λ 226 nm. Inter and intra-day validation demonstrates good reproducibility and accuracy. Limits of quantitation are 0.2 μg/ml for mitotane and DDE, and 0.5 μg/ml for DDA. The method has been evaluated in plasma from 23 patients on mitotane therapy, revealing DDA concentrations 1-18 times higher than the parent compound., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Cantharidin (1) and norcantharidin (2) are potent protein phosphatase 1 and 2A inhibitors that also display high levels of anticancer activity against a broad range of tumor cells lines. Surprisingly, Delta-5,6-ethyl norcantharidin (3, cis-tetrahydrofurano[3,4-c]furan-1,3-dione) displays neither phosphatase inhibition nor anticancer activity. This suggests that the 5,6-ethyl bridge is pivotal to both anti-cancer and protein phosphatase activity. Additionally bioisosteric replacement of the ethereal oxygen has no effect on biological activity nor does modification of the anhydride moiety. Unlike the parent norcantharidin, anhydride ring opening has no effect on either protein phosphatase inhibition or anti-cancer activity. Additionally, this work highlights the discovery of the octyl substituted, cis-5-benzyl-2-hexyltetrahydro-2H,3aH-pyrrolo[3,4-c]pyrrole-1,3-dione, 9p, and the octyl substituted, cis-octyltetrahydro-5H-furo[3,4-c]pyrrole-4,6-dione, 8p, as two new cytotoxic agents which are equipotent (9p) with, and more potent (8p) than norcantharidin., (Crown Copyright (c) 2010. Published by Elsevier Masson SAS. All rights reserved.)

Investigation of an extract of the Australian marine sponge Psammoclema sp. for dynamin I inhibitory activity led to the isolation of four new trihydroxysterols (1-4) related to aragusterol G. These compounds were largely identified by 1D and 2D NMR spectroscopic methods. While 1 was found to be inactive in the dynamin bioassay, bioassays did reveal that compounds 1-4 inhibited the growth of colorectal, breast, ovarian, and prostate cancer cell lines (GI(50) 5-27 microM). The additional insight that these new compounds give to previous SAR studies is discussed briefly.

Cantharidin (1) and its derivatives are of significant interest as serine/threonine protein phosphatase 1 and 2A inhibitors. Additionally, compounds of this type have displayed growth inhibition of various tumour cell lines. To further explore both of these inhibition pathways, a number of amide-acid norcantharidin analogues (15-26) were prepared. Compounds 23 and 24, containing two carboxylic acid residues, showed good PP1 and PP2A activity, with IC(50) values of approximately 15 and approximately 3 mum, respectively. Substituted aromatic amide analogues 45, 48, 49, 52, 53, and 54 also displayed good PP1 and PP2A inhibition, with IC(50) values in the range of 15-10 microM (PP1) and 11-5 microM (PP2A). However, bulky ortho substituents on the aromatic ring caused the aromatic ring to be skewed from the NCO planarity, leading to a decrease in PP1 and PP2A inhibition. A number of analogues, 20, 22, 25 and 46, showed excellent tumour growth inhibition, with 46 in particular being more potent than the lead, norcantharidin 2.

A range of amines was reacted with norcantharidin (2) to provide the corresponding norcantharimides (9-43). Treatment of norcantharidin with allylamine afforded the corresponding allyl-norcantharimide (20) which was amenable to epoxidation (mCPBA, 22) and subsequent ring opening (MeOH/H(+); 23) or alternatively, osmylation (OsO(4)/NMO; 24). These simple synthetic modifications of 2 facilitated the development of a novel series of norcantharimides displaying modest to good broad spectrum cytotoxicity against HT29 and SW480 (colorectal carcinoma); MCF-7 (breast adenocarcinoma); A2780 (ovarian carcinoma); H460 (lung carcinoma); A431 (epidermoid carcinoma); DU145 (prostate carcinoma); BE2-C (neuroblastoma); and SJ-G2 (glioblastoma). Analogues possessing a C(10), C(12) or C(14) alkyl chain or a C(12) linked bis-norcantharimide displayed the highest levels of cytotoxicity.

Norcantharidin (3) is a potent PP1 (IC(50)=9.0+/-1.4 microM) and PP2A (IC(50)=3.0+/-0.4 microM) inhibitor with 3-fold PP2A selectivity and induces growth inhibition (GI(50) approximately 45 microM) across a range of human cancer cell lines including those of colorectal (HT29, SW480), breast (MCF-7), ovarian (A2780), lung (H460), skin (A431), prostate (DU145), neuroblastoma (BE2-C), and glioblastoma (SJ-G2) origin. Until now limited modifications to the parent compound have been tolerated. Surprisingly, simple heterocyclic half-acid norcantharidin analogues are more active than the original lead compound, with the morphilino-substituted (9) being a more potent (IC(50)=2.8+/-0.10 microM) and selective (4.6-fold) PP2A inhibitor with greater in vitro cytotoxicity (GI(50) approximately 9.6 microM) relative to norcantharidin. The analogous thiomorpholine-substituted (10) displays increased PP1 inhibition (IC(50)=3.2+/-0 microM) and reduced PP2A inhibition (IC(50)=5.1+/-0.41 microM), to norcantharidin. Synthesis of the analogous cantharidin analogue (19) with incorporation of the amine nitrogen into the heterocycle further increases PP1 (IC(50)=5.9+/-2.2 microM) and PP2A (IC(50)=0.79+/-0.1 microM) inhibition and cell cytotoxicity (GI(50) approximately 3.3 microM). These analogues represent the most potent cantharidin analogues thus reported.

Fourteen modified norcantharidin analogues have been synthesised and screened for their ability to inhibit the serine/threonine protein phosphatases 1 and 2A. The most potent compounds found were 10 (PP1 IC(50)=13+/-5 microM; PP2A IC(50)=7+/-3 microM) and 16 (PP1 IC(50)=18+/-8 microM; PP2A IC(50)=3.2+/-0.4 microM). Overall, only analogues possessing at least one acidic residue at the former anhydride warhead displayed any PP1 or PP2A inhibitory action. The ability of these analogues to inhibit PP1 and PP2A correlates well with their observed anti-cancer activity against a panel of five cancer cell lines: A2780 (human ovarian carcinoma), G401 (human kidney carcinoma), HT29 (human colorectal carcinoma), H460 (human lung carcinoma) and L1210 (murine leukemia).

Cantharidin (Spanish Fly) is a natural toxin and an inhibitor of protein phosphatases 1 (PP1) and 2A (PP2A), which have key roles in cell cycle progression. We have synthesised two series of demethylated cantharidin analogues, one displaying an open-ring lactone configuration in solution (Novo-1 to Novo-5) similar to cantharidin, the other showing a closed-ring lactone configuration (Novo-6 to Novo-10). In the present study, these ten agents were screened for in vitro PP1 and PP2A inhibition and cellular cytotoxicity in nine cancer cell lines of haematopoietic (L1210, HL60), ovarian (A2780, ADDP), osteo (143B), and colon (HCT116, HT29, WiDr, SW480) origin and one normal colon cell line (CCD-018). The open-ring series (IC50, PPI=2.0-4.8 microM, PP2A=0.2-0.5 microM) maintained the PP2A selectivity of cantharidin (IC50, PPI=1.8 microM, PP2A=0.2 microM), although some were less potent. The closed-ring series (IC50, PPI=12.5->1000 microM, PP2A=5->1000 microM) were considerably less potent inhibitors, confirming the need of ring opening for inhibition. The cytotoxicity (IC50, 72 h, MTT assay) of cantharidin ranged from 6-15 microM, while the new analogues ranged from 14 to >1000 microM. Cytotoxicity of the agents did not consistently parallel the in vitro potency of protein phosphatase inhibition. A number of analogues showed colon cancer selectivity, particularly Novo-6, where the cytotoxicity ranged from 14-88 microM in the colon cancer cells and 275-680 microM in all other cell lines including normal colon cells. The reason for this selectivity was not apparent and may involve additional intracellular targets. Cell cycle analysis showed cantharidin to enhance cell cycle progression as evident from an increased S-phase population and enhanced DNA synthesis, culminating in G2/M arrest and apoptosis. With Novo-1 and Novo-6, the cell cycle changes paralleled the cytotoxicity responses, with the predominant effect of G2/M cell cycle arrest followed by cell death. In conclusion, we have synthesised new anticancer agents that show selective cytotoxicity in colon cancer cells while remaining inactive in normal colon cells, and which mediate their effects via the G2/M phase of the cell cycle.

This study aimed to determine the phytochemical, antioxidant, and anticancer activities of the crude extract and its fractions of Cupaniopsis anacardioides. The results showed that total phenolic content (TPC), their secondary metabolites (flavonoids—TFC; proanthocyanidins—TPro), and antioxidant activity were significantly different between the crude extract and its fractions. The butanol fraction (F3) had the highest levels of TPC, TFC, and TPro, followed by the crude extract, aqueous fraction (F4), dichloromethyl fraction (F2), and hexane fraction (F1). High-Pressure Liquid Chromatography (HPLC) analysis revealed 14 major bioactive compounds were identified in the C. anacardioides extract. Further analysis showed F3 fraction contained the highest levels of the major bioactive compounds, while F1 fraction had the lowest. A similar pattern was observed for antioxidant activities. The crude extract, F3 and F4 fractions were further tested for cytotoxicity against 10 cancer cell lines, including HT29 (colon); U87, SJG2 (glioblastoma); MCF-7 (Breast); A2780 (ovarian); H460 (lung); A431 (skin); Du145 (prostate); BE2-C (neuroblastoma); MIA PaCa-2 (pancreas); and one non-tumour-derived normal breast cell line (MCF10A). Except for Du145 (prostate), the crude extract, F3 and F4 fractions inhibited the cancer cell lines at 100 µg/mL, with F3 possessing greater activity against these cancer cell lines. Future studies are recommended to isolate and identify the major bioactive compounds of the F3 fraction, and further tested their impact against cancer cell lines. This could identify the potential of anticancer agents from C. anacardioides. [ABSTRACT FROM AUTHOR]

Platinum(IV) prodrugs of the [Pt(PL)(AL)(COXi)(OH)]2+ type scaffold (where PL is 1,10-phenanthroline or 5,6-dimethyl-1,10-phenanthroline, AL is 1S,2S-diaminocyclohexane, and COXi is a COX inhibitor, either indomethacin or aspirin) were synthesised and characterised, and their biological activity was explored. MTT assays showed that these complexes exhibit outstanding activity against a range of cancer cell lines, and nanomolar activities were observed. The most potent complex, 4, exhibited a GI50 of 3 nM in the Du145 prostate cancer cell line and was observed to display a 1614-fold increased activity against the HT29 colon cancer cell line relative to cisplatin. ICP-MS studies showed a linear correlation between increased cellular accumulation of the complexes and increased cytotoxicity, while an enzyme immunoassay showed that 1 and 2 inhibited COX-2 at 14 and 1.4 µM, respectively, which is comparable to the inhibition exhibited by indomethacin. These results suggest that while the cytotoxicity of prodrugs 1–4 was influenced by cellular uptake, it was not entirely dependent on either COX inhibition or lipophilicity. [ABSTRACT FROM AUTHOR]

Lipophilic platinum(IV) complexes were synthesised of the type [Pt(HL)(AL)(OH)(R)]2+ and [Pt(HL)(AL)(R)2]2+ (HL = 5,6-dimethyl-1,10-phenanthroline or 1,10-phenanthroline; AL = 1S,2S-diaminocyclohexane and R = increasingly lipophilic carboxylate axial ligands (C10–18)) from hydrophilic platinum(II) precursors that exhibit exceptional anticancer activity. The increased overall lipophilicity of the complexes suggested the formation of spontaneously self-assembled structures in an aqueous environment. The anti-proliferative properties were assessed against one non-cancerous and a panel of cancerous cell lines. Nanomolar levels of activity were observed against several cell lines, with the lowest GI50 of 3.4 nm against the Du145 prostate cancer cell line and over 1100-fold greater activity than cisplatin against HT29 colon carcinoma. RP-HPLC was utilised to establish the relative lipophilicities of each complex. While there seemed to be an increase in cellular accumulation for the lipophilic derivatives in some instances, ICP-MS studies showed no clear correlation between increasing lipophilicity, cellular accumulation and cytotoxicity. [ABSTRACT FROM AUTHOR]

Abstract The aims of this study were to screen the phytochemical content, antioxidant, antimicrobial and cytotoxic properties of the extract and its fractions prepared from Catharanthus roseus (L.) G. Don (C. roseus) stem. C. roseus stem was powdered and extracted with methanol using ultrasound-assisted extraction to obtain the crude extract. The crude extract was further fractioned using liquid-liquid extraction technique to obtain extracts of increasing polarity including n -butanol and residual aqueous fractions. The crude extract and its derived fractions were then subjected to phytochemical screening and assayed for antioxidant, antimicrobial and cytotoxic activities. Results showed that the n -butanol fraction contained the highest levels of saponins and phenolics (3037.54 mg ESE/g and 77.87 mg GAE/g, respectively) and possessed the strongest antioxidant capacity amongst the tested extracts. HPLC analysis revealed that this n -butanol fraction had high levels of apigenin and kaempferol, whereas the aqueous fraction contained a high level of gallic acid. The n -butanol fraction was found to effectively inhibit the activity of Escherichia coli and Staphylococccus lugdunensis. The n -butanol fraction also possessed strong cytotoxic activity in vitro against a wide range of cancer cell lines including A2780 (ovarian), H460 (lung), A431 (skin), MIA PaCa-2 (pancreas), Du145 (prostate), HT29 (colon), MCF-7 (breast), BE2-C (neuroblastoma), SJ-G2, U87 and SMA (glioblastoma) at low doses (GI 50 values of 5.2−21.0 µg/mL). These results indicate that the n -butanol fraction prepared from C. roseus stem is a rich source of bioactive compounds which can be isolated for further evaluation as potential antimicrobial drugs or antitumor therapeutic agents. Highlights • The phytochemical profiles of C. roseus stem and its fractions were elucidated. • The n -butanol fraction contained the highest levels of bioactives and the strongest antioxidant power. • This fraction also exhibited strong inhibitory effect on 11 cancer cell lines. • Microbial growth was effectively inhibited by the n -butanol fraction. [ABSTRACT FROM AUTHOR]

Six platinum(II) complexes of the type [Pt(P L )(A L )] 2 + , where P L is a bidentate pyridyl-1,2,3-triazole “click” ligand and A L is the R , R or S , S isomer of 1.2-diaminocyclohexane, have been synthesised and characterised by several methods including elemental microanalysis, proton NMR spectroscopy and X-ray crystallography. The in vitro cytotoxicity of each complex was assessed in eleven cell lines, revealing moderate to good activity for complexes incorporating 2-(1-phenyl-1H-1,2,3-triazol-4-yl)pyridine. [ABSTRACT FROM AUTHOR]

The Davidson’s plum (DP; Davidsonia pruriens F. Muell) is a fruit native to Australia that is a rich source of phenolic compounds. This study investigated the effects of various extraction solvents (ethanol, methanol, acetone and water) on total phenolic content (TPC), antioxidant capacity (ABTS, DPPH, CUPRAC, FRAP assays) and anti-proliferative activity (MTT, CCK-8 assays) of DP. Our data revealed that extraction solvents significantly affected the physico-chemical, antioxidant and anti-proliferative properties of DP extracts. Within the tested solvents, ethanol was found to be the optimal solvent for extraction of bioactive compounds from DP as its extract had the greatest TPC (94.13 GAE/g), flavonoids (78.33 mg RUE/g), proanthocyanidins (5.33 mg CAE/g), anthocyanidins (2.81 mg CGE/g), as well as possessed the highest antioxidant capacity and anti-proliferative activity against a panel of cancer cell lines. This included cancers of the pancreas, breast, lung, brain, skin, colon and ovary. Therefore, further investigations should be conducted to identify key bioactive compounds to determine the potential for utilization in the nutraceutical and phytopharmaceutical industries. [ABSTRACT FROM AUTHOR]

Platinum anticancer complexes incorporating 2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (44Me2bpy) or 2-(2′-pyridyl)quinoxaline (2pq) as polyaromatic ligands and the S, S or R, R isomer of 1,2-diaminocyclohexane as ancillary ligands in the form [Pt(PL)(AL)]2+ have been synthesised and characterised. X-ray diffraction was used to elucidate the structure and stacking behaviour of the complexes, revealing interesting properties that may impact their biological activity. Pulsed gradient spin-echo NMR experiments elucidated the aggregation behaviour of these complexes in solution. The cytotoxicity of each complex was assessed against the L1210 murine leukaemia, HT29 human colon carcinoma and U87 human glioblastoma cell lines and compared to other complexes within this class. The complexes incorporating 44Me2bpy were found to be the most potent at inhibiting cell growth with IC50 values for the S, S isomer (0.13-0.5 μ M) less than that for cisplatin (0.36-11 μ M), oxaliplatin (0.9-1.8 μ M) or carboplatin (>50 μ M). Most complexes were found to be very effective against HT29 colon carcinoma cells. [ABSTRACT FROM AUTHOR]

Eucalyptus robusta (Sm.) (ER) is a widely distributed tree native to the east coast of Australia, which has also been established in numerous other countries. ER leaves contain high levels of essential oils and are rich in total phenolic compounds (TPC), which have been linked with health benefits; however, there is limited information on the bioactivity of ER leaf extracts. This study aimed to optimise water extraction conditions for TPC, prepare a spray-dried powdered extract and test its physicochemical, antioxidant and anti-proliferative properties. The results showed that optimal water extraction conditions for TPC were 85 °C, 15 min and a water-to-leaf ratio of 20:1 mL/g. Under these conditions, spray-dried powdered extract was prepared with a recovery yield of 85%. The extract was water-soluble and had a TPC level of 407 mg GAE/g. It also possessed potent antioxidant capacity, comparable to pure ascorbic acid, but higher than pure α-tocopherol. In addition, the powdered extract demonstrated significant activity against a panel of cancer cell lines, which included cancers of the pancreas, breast, lung, brain, skin, colon and ovary. Of note, the ER extract exerted a more significant toxic effect on pancreatic cancer (PC) cells compared to gemcitabine, the first line chemotherapeutic agent for PC. We suggest that future studies should purify individual bioactive compounds from ER for further investigation of its potential health promoting and anti-cancer activity. [ABSTRACT FROM AUTHOR]

Abstract: Oroidin (1), (E)-N-(3-(2-amino-1H-imidazol-4-yl)allyl)-4,5-dibromo-1H-pyrrole-2-carboxamide, is a pyrrole alkaloid isolated from the marine sponge Agelas oroides. Routine screening in a panel of twelve cancer cell lines revealed 1 to be poorly cytotoxic with the 50% growth inhibition concentration (GI50) of 42μM in MCF-7 (breast) cells and 24μM in A2780 (ovarian) cells and >50μM in all other cell lines tested. The development of eight focused libraries comprising thirty compounds total identified N-(biphenyl-4-ylmethyl)-1H-pyrrole-2-carboxamide (4l), N-benzyl-4,5-dibromo-1H-pyrrole-2-carboxamide (5a) and N-(biphenyl-4-ylmethyl)-4,5-dibromo-1H-pyrrole-2-carboxamide (5l) as potent inhibitors of cell growth in our panel of cell lines. Of these compounds GI50 values of <5μM were observed with 4l against HT29 (colon) and SW480 (colon); 5a against HT29; and 5l against HT29, SW480, MCF-7, A431 (skin), Du145 (prostate), BE2-C (neuroblastoma) and MIA (pancreas) cell lines. As a cancer class, colon cancer appears to be more sensitive to the oroidin series of compounds, with analogue 5l being the most active. [Copyright &y& Elsevier]