Exploration of some indole-based hydroxamic acids as histone deacetylase inhibitors and antitumor agents

In our search for novel small molecules targeting histone deacetylases, we have designed and synthesized a series of novel hydroxamic acids incorporating indole moiety as a cap group (3a–l). Biological evaluation showed that these hydroxamic acids potently inhibited HDAC2 with IC₅₀ values in submicromolar range and up to tenfold (compound 3j) better than that of SAHA (also known as suberoylanilide hydroxamic acid). In four human cancer cell lines [SW620 (colon), PC-3 (prostate), AsPC-1 (pancreatic), NCI-H23 (lung)], the synthesized compounds that exhibited potent cytotoxicity with several compounds (3k, 3l) were found to be 12- to 77-fold more cytotoxic than SAHA. Docking experiments indicated that the compounds tightly bound to HDAC2 at the active binding site with binding affinities much higher than that of SAHA. Our present results demonstrate that these novel hydroxamic acids are potential for further development as anticancer agents.     

Synthesis and properties of PI polyamide-SAHA conjugate

We have designed and synthesized new types of pyrrole (P)-imidazole (I) polyamide conjugates 1 and 2 possessing a suberoylanilide hydroxamic acid (SAHA) moiety that is a strong inhibitor of histone deacetylase (HDAC). SAHA conjugate 2 was designed to target the promoter region of the p16 tumor suppressor gene. The DNA binding affinity of SAHA conjugate 2 to its target sequence was examined using surface plasmon resonance. HDAC inhibition activity of conjugates 1 and 2 was evaluated using a colorimetric assay. The results demonstrated that even though it possesses the relatively large SAHA moiety, conjugate 2 has high DNA sequence-specific binding properties and moderate HDAC inhibitory activity in vitro. SAHA conjugate 2 was found to cause morphological changes in HeLa cells and to induce selective Histone H3 lysine 9 acetylation.     

Synthesis and in vitro biological evaluation of novel 2-aminoimidazolone derivatives as anti-tumor agents

Novel 2-aminoimidazolone derivatives were synthesized.Most compounds displayed strong anticancer activities against human carcinoma cells in vitro.Compounds 8a,8b and 8j exhibited optimal activity superior to 5-FU in most cancer cells tested.Especially,the lC₅₀s of 8b（12.6-21.5μmol/L） against five tumor cells were 1 -4 fold less than those of 5-FU（18.4-56.1μmol/L） in vitro.Furthermore,comp以ound 8b could induce SMMC-7721 cell apoptosis in a dose-dependent manner.Therefore,our novel findings may provide a new framework for the design of new 2-aminoimidazolone derivatives for the treatment of cancer.     

Identification of novel HDAC8 selective inhibitors through ligand and structure based studies: Exploiting the acetate release channel differences among class I isoforms

Histone deacetylases (HDACs) are key regulators of gene expression and have emerged as crucial therapeutic targets for cancer. Among the HDACs, inhibition of HDAC8 enzyme has been reported to be a novel strategy in the treatment of female-specific cancers. Most of the HDAC inhibitors discovered so far inhibit multiple HDAC isoforms causing toxicities in the clinic thus limiting their potential. Therefore, the discovery of isoform-selective HDAC8 inhibitors is highly desirable. In the present study, a combination of ligand and structure based drug design tools were utilized to build a statistically significant pharmacophore based 3D QSAR model with statistical parameters R²: 0.9964, and Q²: 0.7154, from a series of 31 known HDAC8 inhibitors. Top 1000 hits obtained from Virtual screening of Phase database were subjected to docking studies against HDAC8. Top 100 hits obtained were redocked into HDAC Class I (HDAC 1,2,3) and Class II isoforms (HDAC 4, 6) and rescored with XP Glide Score. Based on fitness score, XP glide score and interacting amino acid residues, five HDAC8 inhibitors (1–5) were selected for in vitro studies. The HDAC8 activity assay followed by enzyme kinetics clearly indicated Compounds 1, 2 and 3 to be potent HDAC8 selective inhibitors with IC₅₀ of 126 pM, 112 nM, and 442 nM respectively. These compounds were cytotoxic to HeLa cells where HDAC8 is overexpressed but not to normal cells, HEK293. Also, they were able to induce apoptosis by modulating Bax/Bcl2, cleavage of PARP and release of Cytochrome C. Molecular Dynamics simulations observed most favorable interaction patterns and presented a rationale for the activities of the identified compounds. Selectivity against HDAC8 was due to exploitation of the architectural difference in the acetate release channel among class I HDAC isoforms.     

Design,synthesis, and biological evaluation of largazole derivatives: alteration of the zinc-binding domain

A new series of largazole analogues in which the side chain was replaced with disulfide groups were synthesized, and their biological activities were evaluated. Compound 8 bearing an octyl moiety showed much better selectivity for HDAC1 over HDAC7 than largazole (320-fold). Structure–activity relationships suggested that the length in the disulfide chain of largazole is important for the selectivity toward HDAC1 over HDAC7.     

Design,synthesis, and biological evaluation of N-hydroxycinnamamide/salicylic acid hybrids as histone deacetylase inhibitors

Novel histone deacetylase(HDAC) inhibitors 9a–l were designed and synthesized by coupling the carboxyl group of salicylic acid(SA) with N-hydroxycinnamamides through various alkylol amines, and their in vitro biological activities were evaluated. The N-hydroxycinnamamide/SA hybrids 9b–f and 9h showed good to moderate anti-tumor activities. Notably, compound 9e had a greater potency, comparable to vorinostat(SAHA), in human colon carcinoma cells, which was probably, or at least partially, attributable to the positive effects of the chain length noted in alkylol amines. Furthermore, the HDAC inhibitory activities of 9e against Hela cell nuclear were also similar to that of vorinostat(SAHA), while the tested compounds 9c–f did not exhibit any isoform selectivity in the inhibition of HDACs. In addition, compound 9e could selectively inhibit tumor cells, but not inhibit non-tumor cell proliferation in vitro. Our findings suggest that the N-hydroxycinnamamide/SA hybrids may hold significant promise as therapeutic agents for the intervention of human cancers.     

Potent Dual BET/HDAC Inhibitors for Efficient Treatment of Pancreatic Cancer

As one of the most aggressive and lethal human malignancies with extremely poor prognosis, there is an urgent demand of more effective therapy for the treatment of pancreatic cancer. Reported here is a new, effective therapeutic strategy and the design of small‐molecule inhibitors that simultaneously target bromodomain and extra‐terminal (BET) and histone deacetylase (HDAC), potentially serving as promising therapeutic agents for pancreatic cancer. A highly potent dual inhibitor ( 13 a ) is identified to possess excellent and balanced activities against BRD4 BD1 (IC₅₀=11 nm ) and HDAC1 (IC₅₀=21 nm ). Notably, this compound shows higher in vitro and in vivo antitumor potency than the BET inhibitor (+)‐JQ1 and the HDAC inhibitor vorinostat, either alone or and in combination, highlighting the advantages of BET/HDAC dual inhibitors for more effective treatment of pancreatic cancer.     

Design,Synthesis, and Evaluation of the Anticancer Properties of a Novel Series of Imidazolone Fused Pyrazolo[1,5‐a]pyrimidine Derivatives

A novel series of imidazolone fused pyrazolo[1,5‐a]pyrimidine derivatives has been designed and synthesized using a convergent approach, and the structures of these compounds were confirmed by ¹H NMR, ¹³C NMR, ESI‐MS, and IR analyses. These new compounds were tested for their in vitro antiproliferative activity using an 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide (MTT) assay. Out of the 20 derivatives prepared in the current study, compounds 8h , 8n , and 8r exhibited good anticancer activities tested against HeLa cells and HepG₂ cells. However, the in vitro anticancer activity of compound 8r against HeLa, HepG₂, and MCF‐7 cell lines is superior to the marketed drugs Paclitaxel and SAHA.     

A Multitargeted Approach: Organorhodium Anticancer Agent Based on Vorinostat as a Potent Histone Deacetylase Inhibitor

The combination of more than one bioactive moiety in a multitargeted anticancer agent may result in synergistic activity of its components. Using this concept, bioorganometallic compounds were designed to feature a metal center, a 2‐pyridinecarbothioamide (PCA), and a hydroxamic acid, which is found in the anticancer drug vorinostat (SAHA). The organometallics showed inhibitory activity in the nanomolar range against histone deacetylases (HDACs) as the key target for SAHA. In particular, the Rh complex was a potent inhibitor of HDAC6 over HDAC1 and HDAC8. Whereas this complex was highly cytotoxic in human cancer cells, it showed low toxicity in hemolysis studies and zebrafish, demonstrating the role of the metal center. For this complex a slightly reduced expression of vascular endothelial growth factor receptor 2 (VEGFR2) was established, which was upregulated by SAHA. This finding indicates that the new organometallics display different modes of action than their bioactive components.     

Synthesis,cytotoxicity, apoptosis and molecular docking studies of novel phenylbutyrate derivatives as potential anticancer agents

Phenylbutyrate (PB), a small aromatic fatty acid, has been known as an interesting compound with the ability of anti-proliferation and cell growth inhibition in cancer cells. In the present study, a series of PB derivatives were synthesized by Passerini multicomponent reaction and their cytotoxic activities against various human cancer cell lines including A549 (non-small cell lung cancer), MDA-MB-231 (breast cancer), and SW1116 (colon cancer) were evaluated. The results revealed that B9, displayed significantly higher in vitro cytotoxicity with IC₅₀ of 6.65, 8.44 and 24.71 μM, against A549, MDA-MB-231 and, SW1116, respectively, in comparison to PB. The effects of these compounds on the proliferation of MCF-10A as non-tumoral breast cell line, showed good selectivity of the compounds between tumorigenic and non-tumorigenic cell lines. Moreover, B9 has indicated apoptosis-inducing activities to MDA-MB-231 cancer cell line in a dose-dependent manner. The molecular docking studies of the synthesized compounds on pyruvate dehydrogenase kinase 2 (PDK2; PDB ID: 2BU8) and histone deacetylase complex (HDAC; PDB ID: 1C3R), as the main targets of PB were applied to predict the binding sites and binding orientation of the compounds to these targets.     

Eight new polyketide metabolites from the fungus Pestalotiopsis vaccinii endogenous with the mangrove plant Kandelia candel (L.) Druce

Seven new prenylated phenols, vaccinols A–G (1–7), and one new naphthalene derivative, vaccinal A (8), together with five known phenol derivatives (9–13) were isolated from Pestalotiopsis vaccinii (cgmcc3.9199) endogenous with the mangrove plant Kandelia candel (L.) Druce (Rhizophoraceae). The new structures were established on the basis of spectroscopic analysis, optical rotation, CD spectra, quantum ECD calculations. Furthermore, the absolute configuration of compound 1 was unambiguously elucidated by single-crystal X-ray diffraction analysis using the Flack parameter. Most new compounds were tested for their antiviral (EV71), cytotoxic, antituberculosis, and anti-inflammatory effects. Among them, compound 8 exhibited in vitro anti-enterovirus 71 (EV71) with IC₅₀ value of 19.2 μM. In addition, 8 showed potent COX-2 inhibitory activity with IC₅₀ value of 1.8 μM.     

Cytotoxic and anti-inflammatory diterpenoids from the Dongsha Atoll soft coral Sinularia flexibilis

Seven new diterpenoids, namely, flexibilisolides C–G (1–5), flexibilisin C (6), and a novel 11,12-secoflexibillin (7), along with seven known compounds, 8–14, were isolated from the Dongsha Atoll soft coral Sinularia flexibilis. The structures of the new metabolites were elucidated by extensive spectroscopic analysis and comparison of the NMR data with those of known analogues. Compounds 1, 8, and 11 were shown to exhibit moderate cytotoxic activity against HeLa and B16 cancer cell lines, and compound 10 was found to exhibit more potent cytotoxic activity against SK-Hep1 and B16 cancer cell lines. Moreover, compounds 1, 2, 8, 9, and 11–14 could significantly inhibit the accumulation of the pro-inflammatory iNOS protein and 1, 8, 11, and 14 could reduce the accumulation of COX-2 protein in LPS-stimulated RAW264.7 macrophage cells.     

Discovery of novel wee1 inhibitors via structure-based virtual screening and biological evaluation

Wee1 plays a critical role in the arrest of G2/M cell cycle for DNA repair before entering mitosis. Many cancer cells have been identified as overexpression of Wee1. In this research, pharmacophore modeling, molecular docking and molecular dynamics simulation approaches were constructed to identify novel potential Wee1 inhibitors. A compound 8 was found to have a novel skeleton against Wee1 with an IC₅₀ value of 22.32 µM and a K_i value of 13.11 µM. Kinetic assays were employed to evaluate the compound 8 as a competitive inhibitor. Compound 8 was tested against A-549 tumor cell lines with IC₅₀ value of 17.8 µM. To investigate the intermolecular interaction of Wee1 and compound 8, further molecular dynamics simulations were performed. It indicates that the binding mode of compound 8 and reference ligand is similar. The active core scaffold of compound 8 could represent a promising lead compound for studying Wee1 and be used for further structural optimization to design more potent Wee1 inhibitors.     

Evaluation of structural,spectral characterization and in vitro cytotoxic activity studies of some polycyclic aromatic compounds

The present study aims to introduce three known and three new stable polycyclic aromatic compounds synthesized. With MALDI-Mass, ¹H and ¹³C NMR spectroscopy, all new compounds were characterized. In the DMF solution were carried out the electrochemical and photophysical properties of the polyaromatic compounds. The compounds are highly fluorescent showing green-red emission when excited at one single wavelength. For the compound 3, it was shown that the highest Stokes Shift (191 nm) appeared which may be due to the excited state energy transfer. The compounds also indicated the blue-orange region of the electromagnetic spectrum strong emission bands. Additionally, compounds 1, 3, 4, and 5 were investigated for their in vitro cytotoxic activities against PC-3 prostate cancer cells, L-929 non-cancerous cells, and MDA-MB-231 breast cancer for 24 h, 48 h and 72 h. The results obtained from the experiment demonstrated that compounds had different cytotoxic activity against cell lines. Compound 3 was indicated to be inactive against L-929 cells and MDA-MB-231 cancer cells, whereas compounds 1, 4 and 5 indicated a dose and time-dependent cytotoxic activity against PC-3, MDA-MB-231, and L-929 cell lines. It was found that the most sensitive cells to compound 5 were MDA-MB-231 human breast cancer cells. Additionally, it became clear that compounds 1 and 3 had significant selectivity for human PC-3 prostate cancer cells, and compounds 1, 4 and 5 had considerable selectivity for human MDA-MB-231 breast cancer cells. Also, the quantum chemical examinations of six organic compounds were conducted at the B3LYP/6-31G level in the gas phase and water. According to calculated results, compound 5 was found to be the best candidate for NLO applications.     

HDAC Inhibitory and Anti-Cancer Activities of Curcumin and Curcumin Derivative CU17 against Human Lung Cancer A549 Cells

Previous research reported that the curcumin derivative (CU17) inhibited several cancer cell growths in vitro. However, its anticancer potential against human lung cancer cells (A549 cell lines) has not yet been evaluated. The purpose of this research was to examine the HDAC inhibitory and anti-cancer activities of CU17 compared to curcumin (CU) in A549 cells. An in vitro study showed that CU17 had greater HDAC inhibitory activity than CU. CU17 inhibited HDAC activity in a dose dependent manner with the half-maximal inhibitory concentration (IC₅₀) value of 0.30 ± 0.086 µg/mL against HDAC enzymes from HeLa nuclear extract. In addition, CU17 could bind at the active pockets of both human class I HDACs (HDAC1, 2, 3, and 8) and class II HDACs (HDAC4, 6, and 7) demonstrated by molecular docking studies, and caused hyperacetylation of histone H3 (Ac-H3) in A549 cells shown by Western blot analysis. MTT assay indicated that both CU and CU17 suppressed A549 cell growth in a dose- and time-dependent manner. Besides, CU and CU17 induced G2/M phase cell cycle arrest and p53-independent apoptosis in A549 cells. Both CU and CU17 down-regulated the expression of p53, p21, Bcl-2, and pERK1/2, but up-regulated Bax expression in this cell line. Although CU17 inhibited the growth of lung cancer cells less effectively than CU, it showed less toxicity than CU for non-cancer cells. Accordingly, CU17 is a promising agent for lung cancer treatment. Additionally, CU17 synergized the antiproliferative activity of Gem in A549 cells, indicating the possibility of employing CU17 as an adjuvant treatment to enhance the chemotherapeutic effect of Gem in lung cancer.     

Design,Synthesis and Cytotoxic Activity Evaluation of Newly Synthesized Amides-Based TMP Moiety as Potential Anticancer Agents over HepG2 Cells

A novel series of amides based TMP moiety was designed, synthesized and evaluated for their antiproliferative as well as enzyme inhibition activity. Compounds 6a and 6b showed remarkable cytotoxic activity against HepG2 cells with IC₅₀ values 0.65 and 0.92 μM, respectively compared with SAHA and CA-4 as reference compounds. In addition, compound 6a demonstrated good HDAC-tubulin dual inhibition activity as it showed better HDAC activity as well as anti-tubulin activity. Moreover, compound 6a exhibited G2/M phase arrest and pre-G1 apoptosis as demonstrated by cell cycle analysis and Annexin V assays. Further apoptosis studies demonstrated that compound 6a boosted the level of caspase 3/7. Caspase 3/7 activation and apoptosis induction were evidenced by decrease in mitochondrial permeability suggesting that activation of caspase 3/7 may occur via mitochondrial apoptotic pathway.     

New phenylpyridone derivatives from the Penicillium sumatrense GZWMJZ-313, a fungal endophyte of Garcinia multiflora

Citridones E-G (1-3), three new phenylpyridone derivatives together with two known curvularins (4 and 5) were isolated from the solid culture of the endophytic fungus Penicillium sumatrense GZWMJZ-313 in Garcinia multiflora. The structures of new compounds were determined in the light of spectroscopic data,X-ray and ECD calculation. Compounds 1 and 3 are racemates, while compound 2 is optically pure.Compounds 1 and 4 showed antibacterial and antifungal activities against Staphylococcus aureus,Pseudomonas aeruginosa, Clostridium perfringens, Escherichia coli and Candida albicans with MIC values ranging from 8 μg/mL to 64 μg/mL.     

Target Design of Novel Histone Deacetylase 6 Selective Inhibitors with 2-Mercaptoquinazolinone as the Cap Moiety

Epigenetic alterations found in all human cancers are promising targets for anticancer therapy. In this sense, histone deacetylase inhibitors (HDACIs) are interesting anticancer agents that play an important role in the epigenetic regulation of cancer cells. Here, we report 15 novel hydroxamic acid-based histone deacetylase inhibitors with quinazolinone core structures. Five compounds exhibited antiproliferative activity with IC₅₀ values of 3.4–37.8 µM. Compound 8 with a 2-mercaptoquinazolinone cap moiety displayed the highest antiproliferative efficacy against MCF-7 cells. For the HDAC6 target selectivity study, compound 8 displayed an IC₅₀ value of 2.3 µM, which is 29.3 times higher than those of HDAC3, HDAC4, HDAC8, and HDAC11. Western blot assay proved that compound 8 strongly inhibited tubulin acetylation, a substrate of HDAC6. Compound 8 also displayed stronger inhibition activity against HDAC11 than the control drug Belinostat. The inhibitory mechanism of action of compound 8 on HDAC enzymes was then explored using molecular docking study. The data revealed a high binding affinity (−7.92 kcal/mol) of compound 8 toward HDAC6. In addition, dock pose analysis also proved that compound 8 might serve as a potent inhibitor of HDAC11.     

Novel quinolinone alkaloids bearing a lignoid moiety and related constituents in the leaves of Melicope denhamii

Six novel quinolinone alkaloids bearing a phenylpropanoid or a coumarin moiety, named melicodenines C–H (1–6), two new cinnamyl alcohol derivatives, named melicodins A (7) and B (8), and a new coumarinolignan, named melicodin C (9), were isolated from the leaves of Melicope denhamii (Seem.) T. G. Hartley. Their structures were established by spectroscopic analyses including extensive 2D-NMR experiments. Compounds 1–5 and 9 possess a cyclobutane ring and are hypothetically produced by a [2+2] cycloaddition, whereas compound 6 is presumed to form through a Diels–Alder cycloaddition followed by the elimination of an acetone molecule. Ten quinolinone alkaloids (1–6, 10–13) and a coumarinolignan (9) were tested for anti-proliferative activity against DLD-1 human colon cancer cells. Melicodenine G (5) showed the most potent inhibitory activity, causing the induction of apoptosis with an IC₅₀ value of 9.4±0.3 μM.     

Synthesis and biological evaluation of novel triazole derivatives as antifungal agents

A series of 1-(benzylamino)-2-(2,4-difluorophenyl)-3-(1H-1,2,4-triazol-l-yl)propan-2-ols compounds were synthesized and evaluated for their antifungal activities in vitro.The results showed that compounds 6A and 6B exhibited good antifungal activity.Compound 6A8 showed the strongest antifungal activity,which was significantly higher than that of the lead compounds and positive-control drugs Fluconazole and Itraconazole.In particular,the antifungal activity of compound 6A8 against Candida albicans and Candida krusei(MIC80 both at 0.00097μg/mL) was 515 and 64 times that of Fluconazole,respectively.The structure-activity relationships of the synthesized compounds were discussed,and the docking model of the target compounds with fungal lanosterol 14α-demethylase (CYP51) was analyzed.