Synthesis and biological evaluation of new bisindole-imidazopyridine hybrids as apoptosis inducers

A series of diindolylmethanes (5a-t) were designed, synthesized, and examined for their cytotoxicity against four human cancer cell lines like prostate (DU-145), lung (A549), breast (MCF-7) and cervical cancer (HeLa). These results revealed that among all the hybrids, two (5k and 5r) were identified and exhibited significant cytotoxic effect against A549 cancer cells with IC₅₀ values of 1.65 ± 0.3 and 1.80 ± 0.8 µM respectively. To investigate the reasons for the cytotoxic activity, the conventional biological assays were carried out with 5k and 5r on the A549 cancer cells. Both hybrids led to the arrest of A549 cell lines at the G2/M phase of the cell cycle and strongly induced apoptosis. Further the apoptotic effects of 5k and 5r were confirmed by ROS, annexin-V FITC, and mitochondrial membrane potential. Moreover, structure–activity relationships were elucidated with various substitutions on these hybrids.     

Synthesis of substituted biphenyl methylene indolinones as apoptosis inducers and tubulin polymerization inhibitors

A new series of biphenyl methylene indolinones has been designed, synthesized and evaluated for their in vitro antiproliferative activity against various cancer cell lines like DU-145 (prostate cancer cell line), 4T1 (mouse breast cancer cell line), MDA-MB-231 (human breast cancer cell line), BT-549 (human breast cancer cell line), T24 (human urinary bladder carcinoma cell line), and HeLa (cervical cancer cell line). Among the series, compound 10e showed potent in vitro cytotoxic activity against HeLa and DU-145 cancer cell lines with IC₅₀ value of 1.74 ± 0.69 µM and 1.68 ± 1.06 µM respectively. To understand the underlying mechanism of most potent cytotoxic compound 10e, various mechanistic studies were carried out on DU-145 cell lines. Cell cycle analysis results revealed that these conjugates affect both G0/G1 and G2/M phase of the cycle, tubulin binding assay resulted that compound 10e interrupting microtubule network formation by inhibiting tubulin polymerization with IC₅₀ value of 4.96 ± 0.05 μM. Moreover, molecular docking of 10e on colchicine binding site of the tubulin explains the interaction of 10e with tubulin. Clonogenic assay indicated inhibition of colony formation by compound 10e in a dose dependent manner. In addition, morphological changes were clearly observed by AO/EB and DAPI staining studies. Moreover, ROS detection using DCFDA, JC-1, and annexin V-FITC assays demonstrated the significant apoptosis induction by 10e.     

Tomensides A–D,new antiproliferative phenylpropanoid sucrose esters from Prunus tomentosa leaves

To search for novel cytotoxic constituents against cancer cells as lead structures for drug development, four new 3-phenylpropanoid-triacetyl sucrose esters, named tomensides A–D (1–4), and three known analogs (5–7) were isolated from the leaves of Prunus tomentosa. Their structures were elucidated by spectroscopic analyses (1D, 2D NMR, CD and HRESIMS). The cytotoxic activities of all isolates against four human cancer cell lines (MCF-7, A549, HeLa and HT-29) were assayed, and the results showed that these isolates displayed stronger inhibitory activities compared with positive control 5-fluorouracil. Tomenside A (1) was the most active compound with IC₅₀ values of 0.11–0.62 μM against the four tested cell lines. The structure–activity relationship (SAR) of the isolates was also discussed. The primary screening results indicated that these 3-phenylpropanoid-triacetyl sucrose esters might be valuable source for new potent anticancer drug candidates.     

Cytotoxic clerodane diterpenoids from the leaves of Casearia kurzii

A phytochemical investigation to obtain bioactive substances as lead compounds or agents for cancer led to the obtainment of six new clerodane diterpenoids, designated as kurzipenes A–F (1–6), from the leaves of Casearia kurzii. Their structures were elucidated on the basis of NMR spectroscopic data analysis and the absolute configurations were confirmed by the time-dependent density functional theory (TDDFT) electronic circular dichroism (ECD) calculations. The cytotoxic activities of compounds 1–6 were evaluated against human lung cancer A549 cell line, human cervical cancer Hela cell line, and human hepatocellular carcinoma HepG2 cell line. Most diterpenoids showed potent cytotoxicities against the three selected cancer cell lines. The preliminary mechanism studies revealed that the most active compound 2, with an IC₅₀ value of 5.3 μM against Hela cells, induced apoptosis and arrested the Hela cell cycle at the G0/G1 stage to exert cytotoxic effects.     

Imidazo[1,2-a]pyridines linked with thiazoles/thiophene motif through keto spacer as potential cytotoxic agents and NF-κB inhibitors

A series of new imidazo[1,2-a]pyridine linked with thiazole/thiophene motif through a keto spacer were synthesized and tested for their cytotoxic potential against three human cancer cell lines including A549, HeLa and U87-MG using MTT assay. Compounds A2, A3, A4, C1 and C2 showed cytotoxicity against all the three cell lines. The selectivity index for compound A4 for A549 and HeLa cells was comparable to that of doxorubicin. Among the synthesized compounds, B5 showed the maximum inhibition of NF-κB activity as ascertained by NF-κB reporter assay (IC₅₀?=?6.5?±?0.6?µM). Treatment of NCI-H23 cells (EGFR overexpressed, KRAS G12V mutant) with erlotinib and gefitinib along with compounds A4 and B5 indicated synergistic and additive potential of combination therapy.     

Five new quassinoids and cytotoxic constituents from the roots of Eurycoma longifolia

Eurycoma longifolia has been widely used for various traditional medicinal purposes in South-East Asia. In this study, five new quassinoids, eurylactone E (1), eurylactone F (2), eurylactone G (3), eurycomalide D (4), and eurycomalide E (5), along with ten known quassinoids (6–15) were isolated from the roots of E. longifolia. Their structures were determined by extensive spectroscopic methods, including 1D and 2D NMR, and MS spectra data. Among the isolated compounds, 13β-methyl,21-dihydroeurycomanone (6) has been reported as a synthetic derivative. However, it was isolated from the natural product for the first time in this study. The cytotoxic activities of fifteen compounds were evaluated against human lung cancer cell line, A549 and human cervical cancer cell line, HeLa.     

Synthesis of benzo[d]imidazo[2,1-b]thiazole-chalcone conjugates as microtubule targeting and apoptosis inducing agents

A series of benzo[d]imidazo[2,1-b]thiazole-chalcone conjugates (5a-aa) were designed, synthesized and evaluated for their cytotoxic potency against a panel of human cancer cell lines like lung (A-549), breast (MDA MB-231), prostrate (DU-145) and colon cancer (HT-29). Preliminary results revealed that some of these conjugates like 5d and 5u exhibited significant antiproliferative effect against human breast cancer (MDA MB-231) with IC₅₀ values of 1.3 and 1.2 µM respectively. To investigate the mechanistic aspects underlying the activity, the detailed biological studies of these promising conjugates (5d and 5u) were carried out on the MDA MB-231 cancer cells. Flow cytometric analysis revealed that these conjugates induce cell-cycle arrest in the G2/M phase. The tubulin polymerization assay suggests that these conjugates effectively inhibit microtubule assembly. In addition, morphological changes, reactive oxygen species (ROS) detection by 2′, 7′–dichlorofluorescin diacetate (DCFDA) and annexin V–FITC/PI assays indicate that 5d and 5u induces apoptosis. Furthermore, in silico computational studies, including molecular docking studies have been carried out to rationalise the binding modes of these conjugates with the tubulin protein.     

Synthesis and anticancer evaluation of 3-aryl-6-phenylimidazo[2,1-b]thiazoles

A series of new 3,6-diphenylimidazo[2,1-b]thiazole derivatives (4a–l) are synthesized and evaluated for their anticancer activity. Some of the synthesized compounds have shown potent anti-proliferative activity against HeLa, MDA-MB-231, A549 and THP1 human cancer cell lines. Among the active compounds, 3-(3-trifluoromethylphenyl)-6-phenylimidazo[2,1-b]thiazole (4j) has caused significant cytotoxicity in HeLa cells, with IC₅₀ as low as 6.5 μM. Compound 4j has induced caspase-3 and caspase-8 activation, leading to an apoptotic cell death. FACS analysis has revealed that compound 4j arrests cells in G0/G1 phase. The presence of 3-(3-trifluoromethylphenyl)- or 3-(3-chlorophenyl)-substituent, in that order, on the 6-phenylimidazo[2,1-b]thiazole impacts more positively than other aryl-substituents, on the anti-proliferative properties of these compounds.     

Design and synthesis of 1,2,3-triazolo-phenanthrene hybrids as cytotoxic agents

A series of new 1,2,3-triazolo-phenanthrene hybrids has been synthesized by employing Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. These compounds were evaluated for their in vitro cytotoxic potential against various human cancer cell lines viz. lung (A549), prostate (PC-3 and DU145), gastric (HGC-27), cervical (HeLa), triple negative breast (MDA-MB-231, MDA-MB-453) and breast (BT-549, 4T1) cells. Among the tested compounds, 7d displayed highest cytotoxicity against DU145 cells with IC₅₀ value of 1.5 ± 0.09 µM. Further, the cell cycle analysis shown that it blocks G0/G1 phase of the cell cycle in a dose dependent manner. In order to determine the effect of compound on cell viability, phase contrast microscopy, AO/EB, DAPI, DCFDA and JC-1 staining studies were performed. These studies clearly indicated that the compound 7d inhibited the cell proliferation of DU145 cells. Relative viscosity measurements and molecular docking studies indicated that these compounds bind to DNA by intercalation.     

Cytotoxic ent-Abietane-type diterpenoids from the roots of Euphorbia ebracteolata

Euphoroids A–C (1–3), three new ent-abietane-type diterpenoids, together with ten known analogues (4–13) were obtained from the roots of Euphorbia ebracteolata. The structures of these compounds were determined by extensive spectroscopic data analysis, including UV, HRESIMS, 1D-, and 2D-NMR data. The inhibitory effects of compounds 1–13 on human cancer cells were determined using the MTT assay. The results revealed that new compounds 2 and 3 showed moderate cytotoxic activities against human cancer cell lines. Especially, compound 3 displayed selective cytotoxic effect agains cancer cell lines.     

One-pot synthesis and biological evaluation of N-(aminosulfonyl)-4-podophyllotoxin carbamates as potential anticancer agents

A series of N-(aminosulfonyl)-4-podophyllotoxin carbamates were synthesized via the Burgess-type intermediate, and their antiproliferative activities were evaluated. Most of them possessed more potent cytotoxic effects against four human tumor cell lines (HeLa, A-549, HCT-8 and HepG2) and less toxic to normal human fetal lung fibroblast WI-38 cells than etoposide. In particular, N-(morpholinosulfonyl)-4-podophyllotoxin carbamate (9) exhibited the most potent activity towards these four tumor cells with IC₅₀ values in the range of 0.5–16.5 μM. Furthermore, immunofluorescence analysis revealed that 9 induced cell apoptosis by up-regulating the expression of p53 and ROS. Meanwhile, 9 effectively inhibited tubulin polymerization and microtubule assembly at cellular levels in HeLa cells. In addition, 9 could induce cell cycle arrest in the G2/M phase in HeLa cells by up-regulating levels of cyclinB1 and cdc2 and decreasing the expression of p-cdc2. These results indicated that 9 had potential for further development as anticancer agents.     

Synthesis and biological evaluation of imidazo[2,1-b]thiazole-benzimidazole conjugates as microtubule-targeting agents

A series of imidazo[2,1-b]thiazole-benzimidazole conjugates were synthesized and evaluated for their antiproliferative activity against four human cancer cell lines i.e.; HeLa (cervical), A549 (lung), MCF-7 (breast) and DU-145 (prostate) along with normal HEK-293 cell line. Amongst them, conjugate 6d displayed significant cytotoxicity against human lung cancer cell line, A549 with IC₅₀ value 1.08 µM. Further, cell cycle analysis revealed that this compound arrested the cell cycle at G2/M phase in A549 cells. Furthermore, the tubulin polymerization assay results suggest that this conjugate (6d) exhibits significant inhibitory effect on the tubulin assembly with an IC50 value of 1.68 µM. Moreover, the apoptotic inducing properties of compound 6d was confirmed by Hoechst staining, measurement of mitochondrial membrane potential (ΔΨm) and annexin V-FITC assay. Further, molecular docking studies revealed that compound 6d occupied the colchicine binding site.     

Steroidal alkaloids from Solanum erianthum and their anti-breast cancer properties

Two new glycoalkaloids, erianosides A (1) and B (2) along with five known compounds (3–7) were isolated from the leaves of Solanum erianthum. Their structures were elucidated from analyses of spectroscopic data and all isolates were tested for in vitro cytotoxic activity against human breast cancer cell lines (BT-549, MDA-MB-231, T74D, and MCF-7). Solasonine (5) and solamargine (6) were active against the aforementioned four cancer cell lines with IC₅₀ values of 27.26–35.89 and 5.84–10.13 μM, respectively. Erianoside A (1) (T74D: IC₅₀, 56.39 µM) and solasodine (3) (BT-549 and MDA-MB-231: IC₅₀, 59.15 and 75.63 µM, respectively) had moderate cytotoxic effects towards some cell lines in the panel.     

Cytotoxic cycloartane triterpenoids from the leaves of Markhamia stipulata var. canaense

From the most cytotoxic fraction of the ethyl acetate extract of Markhamia stipulata var. canaense V.S. Dang leaves, two new cycloartane-type triterpenoids, named Markhacanasin A (1) and Markhacanasin B (2); were isolated by various chromatographic methods Their structures were elucidated by IR, UV, HR-ESI–MS, NMR (1D & 2D) experiments. The cytotoxicity of two new compounds against five human cancer cell lines (HeLa, HepG2, MCF-7, Jurkat and NCI-H460) were evaluated by SRB assay. As results, 1 exhibited significant cytotoxic activity against all cancer cell lines (IC₅₀ ranged from 14.72 to 29.55 μM) while 2 did not show activity.     

Syntheses of 6-(2-hydroxy-6-phenylhexyl)-5,6-dihydro-2H-pyran-2-one derivatives and their cytotoxicities

The cytotoxicities against cancer cells (HL-60, HeLa) and insect cells (Sf9) of four stereoisomers of 6-(2-hydroxy-6-phenylhexyl)− 5,6-dihydro-2H-pyran-2-one (1) were evaluated, and then their structure-activity relationships examined. The 2′-dehydroxy derivative 5 of (6 R,2′R)- and (6 R,2′S)-1 showed the highest activity against HeLa cells (IC₅₀ = 1.4 μM). To evaluate the effect of the 2′-hydroxy group of 1, 6R-and 6S-oxetane derivatives were also synthesized and their activities examined. Against HeLa and HL-60 cells, the activities of the less potent stereoisomers were enhanced 3–4-fold by the introduction of the oxetane moieties at the 2′-position. Against the insect cell line (Sf9), phenyl derivative 7 showed the highest activity with an IC₅₀ value of 8.0 μM.     

Two novel neo-clerodane diterpenoids from Scutellaria barbata

Two novel neo-clerodane diterpenoids, barbatellarines A (1) and B (2), were isolated from the whole plants of Scutellaria barbata, along with the known compound scutebarbatine F (3). The chemical structures and relative stereochemistry of the isolated compounds were established by NMR (1D and 2D) and mass spectroscopic analyses. Compounds 2 and 3 were evaluated for in vitro cytotoxic activity against the HL-60 (human leukemia), MCF7 (human breast cancer), and LLC (Lewis lung carcinoma) cancer cell lines. Compound 2 exhibited weak cytotoxic activity against HL-60 cells, with an IC₅₀ value of 41.4 μΜ.     

(−)-9′-O-(α-l-Rhamnopyranosyl)lyoniresinol from Lespedeza cuneata suppresses ovarian cancer cell proliferation through induction of apoptosis

Lespedeza cuneata (Dum. Cours.) G. Don. (Fabaceae), known as Chinese bushclover or sericea lespedeza, has been used in traditional medicine to treat diabetes, hematuria, and insomnia, and it has been reported that bioactive compounds from L. cuneata possess various pharmacological properties. However, there has been no study to determine the active compounds from L. cuneata with potential activity against ovarian cancer. This study aimed to isolate cytotoxic compounds from L. cuneata and identify the molecular mechanisms underlying the apoptosis pathway in ovarian cancer cells. Based on cytotoxic activity identified in the screening test, chemical investigation of the active fraction of L. cuneata led to the isolation of nine compounds including four lignanosides (1–4), three flavonoid glycosides (5–7), and two phenolics (8–9). Cytotoxicity and the molecular mechanism were examined by methyl thiazolyl tetrazolium (MTT) assay and Western blot analysis. Of the isolated compounds, (?)-9′-O-(α-l-rhamnopyranosyl)lyoniresinol (3) demonstrated the strongest effect in suppressing A2780 human ovarian carcinoma cell proliferation in a dose-dependent manner, with an IC₅₀ value of 35.40?±?2.78?μM. Control A2780 cells had normal morphology, whereas cell blebbing, shrinkage, and condensation were observed after treatment with compound 3. Western blotting analysis showed that compound 3 inhibited A2780 human ovarian cancer cell viability by activating caspase-8, caspase-3, and PARP, which contributed to apoptotic cell death. These results suggest that (?)-9′-O-(α-l-rhamnopyranosyl)lyoniresinol (3) has potent anticancer activities against A2780 human ovarian carcinoma cells through the extrinsic apoptotic pathway. Therefore, (?)-9′-O-(α-l-rhamnopyranosyl)lyoniresinol is an excellent candidate for the development of novel chemotherapeutics.     

Five new triterpenoid saponins from the Roots of Camellia oleifera C. Abel with cytotoxic activities

Five new triterpenoid saponins, oleiferosides P–T (1–5) were isolated from the EtOH extract of the roots of Camellia oleifera C. Abel. The structures of saponins 1–5 were elucidated on the basis of integrated spectroscopic techniques. All the compounds were characterized to be oleanane-type saponins with sugar moieties linked to the C-3 of the aglycone. By using the MTT assay, an in vitro analysis of the cytotoxic activities of these saponins on the human tumor cell lines (lung adenocarcinoma A549 cells, hepatic carcinoma SMMC-7721 cells and breast cancer MCF-7 cells). Among them, compound 4 showed a certain cytotoxic activity against all the tested cell lines.     

Five new cucurbitane triterpenoids with cytotoxic activity from Hemsleya jinfushanensis

Five new cucurbitane triterpenoids (hemslepenside B–E (1–3 and 5)), one new cucurbitane (16,25-O-diacetyl-cucurbitane F (4)), and six analogues (6–11) were isolated from the roots of Hemsleya jinfushanensis. The structures of 1–5 were elucidated using infrared absorption spectroscopy (IR), high resolution electrospray ionization mass spectrometry (HR-ESI-MS), and nuclear magnetic resonance spectroscopy (NMR). These five new compounds exhibited cytotoxic effects against lung adenocarcinoma (H460), colon cancer (SW620) and human prostate cancer cells (DU145), and compound 4 showed significant cytotoxic activity, with IC₅₀ values of 0.046, 0.18 and 0.87 μg/mL. This finding suggests that cucurbitane triterpenoids isolated from H. jinfushanensis should be studied further as potential anti-cancer drugs.     

Cytotoxic diterpenes from roots of Crossopetalum gaumeri,a Celastraceae species from Yucatan Peninsula

Four new diterpenes, crossogumerins A–D (1–4) along with six known ones (5–10) were isolated from the root bark of Crossopetalum gaumeri, an endemic medicinal plant from the Yucatan Peninsula. Their structures were elucidated on the basis of 1D and 2D NMR techniques, including HMQC, HMBC, and ROESY experiments. Compounds 1–5, 8–10 were evaluated for cytotoxicity against HeLa (carcinoma of the cervix) and Hep-2 (lung carcinoma) human tumor cells lines and against normal Vero cells (African green monkey kidney) in lag and log phase of growth. Podocarpane diterpenes, crossogumerin B (2) and nimbiol (10), exhibited the highest activity against HeLa cells (IC₅₀ values of 3.1 and 8.1 μM, respectively), but also selectivity on Vero cells (SI 22.6 and 7.5, respectively). The preliminary SAR studies suggest that an epoxy moiety in ring B and a hydrogen bond-donor group strategically positioned in the diterpene core are important requirements for cytotoxicity and selectivity.