Antibacterial chalcones––bioisosteric replacement of the 4′-hydroxy group

Antibacterial, antifungal and antimycobacterial activities of some pyrazoline, hydrazone and chalcone derivatives

Twenty-seven previously reported chalcones and their pyrazoline and hydrazone derivatives as well as two further chalcones have been screened for their antimicrobial, antifungal and antimycobacterial activities against standard microbial strains and drug resistant isolates. The minimum inhibitory concentration (MIC) value of each compound was determined by a two-fold serial microdilution technique. The compounds were found to possess a broad spectrum of antimicrobial activities with MIC values of 8–128 μg/mL. One compound [(E)-1-(4-hydroxyphenyl)-3-p-tolylprop-2-en-1-one] had equal activity with gentamycin (8 μg/mL) against Enterococcus faecalis. Chalcones were found to be more active than their hydrazone and 2-pyrazoline derivatives against Staphylococcus aureus ATCC 29213 and E. faecalis ATCC 29212.

Synthesis, docking and ADMET studies of novel chalcone triazoles for anti-cancer and anti-diabetic activity

A series of novel chalcone-triazole derivatives were synthesized and screened for in vitro anticancer activity on the human cancer cell lines IMR32 (neuroblastoma), HepG2 (hepatoma) and MCF-7 (breast adenocarcinoma), DU-145 (prostate carcinoma), and A549 (lung adenocarcinoma). Among the tested compounds, 4r showed the most promising anticancer activity in all the cell lines whereas, compounds 4c (IC50 65.86 μM), 4e (IC50 66.28 μM), 4o (IC50 35.81 μM), 4q (IC50 50.82 μM) and 4s (IC50 48.63 μM) showed better activity than the standard doxorubicin (IC50 69.33 μM) in A549 cell line alone. Rat intestinal α-glucosidase inhibitory activity of the synthesized derivatives showed 4m (IC50 67.77 μM), 4p (IC50 74.94 in μM) and 4s (IC50 102.10 μM) as most active compared to others. The in silico docking of synthesized derivatives 4a-4t with DNA topoisomerase IIα revealed the LibDock score in the range of 71.2623-118.29 whereas, compounds 4h, 4m, 4p and 4s with docking target α-glucosidase were in the range of 100.372-107.784.

Synthesis, anticancer and radiosensitizing evaluation of some novel sulfonamide derivatives

In this study, novel series of sulfonamide derivatives were synthesized starting from 2-cyanoacetyl)hydrazono)ethyl)phenyl)benzenesulfonamide 4a and 2-cyanoacetyl)hydrazono)ethyl)phenyl)-4-methylbenzenesulfonamide 4b. Different biologically active moieties as pyrazol, thiophene, pyridine and pyrimidines were introduced in order to investigate their in-vitro anticancer activity, in addition to a novel series of sulfonamide chalcones were synthesized from the reported 4-acetyl-N-(P-tolyl) benzenesulfonamide 3b. The newly synthesized sulfonamide derivatives were characterized by FT-IR, (1)H NMR, (13)C NMR, mass spectroscopy and elemental analyses and were tested for their in-vitro anticancer activity against human tumor liver cell line (HEPG-2). The most potent compounds in this study were compounds 4a, 4b, 5a, 6a, 6b, 8, 9, 11, 13, 18 and 19 which showed higher activity than doxorubicin with IC50 ranging from 11.0 to 31.8 μM. Additionally, eight compounds among the most potent were evaluated for their ability to enhance the cell killing effect of γ-radiation.

Synthesis, biological evaluation and structure-activity relationships of new quinoxaline derivatives as anti-Plasmodium falciparum agents

We report the synthesis and antimalarial activities of eighteen quinoxaline and quinoxaline 1,4-di-N-oxide derivatives, eight of which are completely novel. Compounds 1a and 2a were the most active against Plasmodium falciparum strains. Structure-activity relationships demonstrated the importance of an enone moiety linked to the quinoxaline ring.

Cajachalcone: An Antimalarial Compound from Cajanus cajan Leaf Extract

Cajanus cajan L, a member of the family Fabaceae, was identified from the Nigerian antimalarial ethnobotany as possessing antimalarial properties. The bioassay-guided fractionation of the crude methanol extract of C. cajan leaves was done in vitro using the multiresistant strain of Plasmodium falciparum (K1) in the parasite lactate dehydrogenase assay. Isolation of compound was achieved by a combination of chromatographic techniques, while the structure of the compound was elucidated by spectroscopy. This led to the identification of a cajachalcone, 2′,6′-dihydroxy-4-methoxy chalcone, as the biologically active constituent from the ethyl acetate fraction. Cajachalcone had an IC₅₀ value of 2.0 μg/mL (7.4 μM) and could be a lead for anti-malarial drug discovery.

Targeting adenosine receptors with coumarins: synthesis and binding activities of amide and carbamate derivatives

OBJECTIVES

With the aim of finding the structural features governing binding activity and selectivity against adenosine receptors (ARs), several 3-subtituted coumarins with amide (compounds 3-6) and carbamate (7-9) functions were synthesized. To study its possible influence on the binding activity and selectivity, a hydroxyl substituent was also introduced at position 4 of the coumarin moiety.

METHODS

A new series of coumarins (3-9) were synthesized and evaluated by radioligand binding studies towards ARs.

KEY FINDINGS

None of the 4-hydroxy derivatives (4, 8 and 9) showed binding affinity for any of the ARs. None of the compounds interacted with the hA(2B) AR (K(i) > 100,000 nM). Compounds 3, 5, 6 and 7 had different activity profiles with dissimilar binding affinity and selectivity towards human A₁, A(2A) and A₃ ARs.

CONCLUSIONS

 The most remarkable derivative is compound 7, which presents the best affinity and selectivity for the A₃ adenosine receptor (K(i) = 5500 nM).

Antimalarial activity of newly synthesized chalcone derivatives in vitro

Twenty-seven novel chalcone derivatives were synthesized using Claisen-Schmidt condensation and their antimalarial activity against asexual blood stages of Plasmodium falciparum was determined. Antiplasmodial IC(50) (half-maximal inhibitory concentration) activity of a compound against malaria parasites in vitro provides a good first screen for identifying the antimalarial potential of the compound. The most active compound was 1-(4-benzimidazol-1-yl-phenyl)-3-(2, 4-dimethoxy-phenyl)-propen-1-one with IC(50) of 1.1 μg/mL, while that of the natural phytochemical, licochalcone A is 1.43 μg/mL. The presence of methoxy groups at position 2 and 4 in chalcone derivatives appeared to be favorable for antimalarial activity as compared to other methoxy-substituted chalcones. Furthermore, 3, 4, 5-trimethoxy groups on chalcone derivative probably cause steric hindrance in binding to the active site of cysteine protease enzyme, explaining the relative lower inhibitory activity.

(2E)-1-(2,6-Dichloro-3-fluoro-phen-yl)-3-(4-fluoro-phen-yl)prop-2-en-1-one

In the title compound, C(15)H(8)Cl(2)F(2)O, the C=C double bond is in the E configuration. In the cyrstal, C-H⋯O hydrogen bonds connect the mol-ecules into chains along the c axis. A π-π inter-action of 3.628 (1) Å is also observed between two polyhalogenated benzene rings. The dichloro-substituted ring exhibits partial disorder over two sets of sites, with site-occupancy factors of 0.573 (3) and 0.427 (3).

Antibacterial activity of chalcones, hydrazones and oxadiazoles against methicillin-resistant Staphylococcus aureus

The increase in antibiotic resistance due to multiple factors has encouraged the search for new compounds which are active against multidrug-resistant pathogens. In this context, chalcones, dihydrochalcones, hydrazones and oxadiazoles were tested against Staphylococcus aureus ATCC 25923 and methicillin-resistant S. aureus (MRSA) isolates, which were obtained from clinical laboratories and were characterized as MRSA using traditional and molecular methods. Among 65 tested compounds, two chalcones, one dihydrochalcone and two hydrazones were active against MRSA. Based on the minimal inhibitory concentration and cytotoxicity, hydrazones provided a better selectivity index than chalcones. Active hydrazones are promising antibiotic-like substances and they should be the subject of further microbiological studies.

Design, synthesis and cytotoxicity of novel chalcone analogs derived from 1-cyclohexylpyrrolidin-2-one and 2,3-dihydrobenzo[f]chromen-1-one

Two divergent series of novel chalcone analogs, one derived from 1-cyclohexylpyrrolidin-2-one and the other derived from 1-benzo[f]chromanone, were designed, synthesized and evaluated for cytotoxicity against two murine cancer cell lines. Two 1-benzo[f]chromanone analogs, 4g and 4j yielded moderate toxicity against both melanoma B16 and lymphoma L1210 cell lines with IC(50) values between the range of 5 and 6 µM. With an IC(50) value of 3.4 µM, compound 4g was also active against human MDA-MB-435 melanoma cells. X-ray structures of the β-hydroxy ketone product (4a) and the α,β-unsaturated ketone (4h) were collected, and confirm the syn-configuration between the carbonyl moiety and the β-vinylic proton in 4h. X-ray structures of two 1-cyclohexylpyrrolidin-2-one derivatives were also obtained, and both showed an E-configuration for the double bond.

(2E)-1-(4-Amino-phen-yl)-3-(2,4-dichloro-phen-yl)prop-2-en-1-one

The title compound, C(15)H(11)Cl(2)NO, is approximately planar (r.m.s. deviation = 0.062 Å) and contains a single C=C double bond in a trans (E) configuration. The crystal packing is stabilized by intermolecular N-H⋯N and N-H⋯O inter-molecular hydrogen bonding.

Recent progress in therapeutic applications of chalcones

INTRODUCTION

Chalcones are a group of plant-derived polyphenolic compounds belonging to the flavonoids family that possess a wide variety of cytoprotective and modulatory functions, which may have therapeutic potential for multiple diseases. Their physicochemical properties seem to define the extent of their biological activity.

AREAS COVERED

A comprehensive synopsis of recent patent literature (2005 - 2011) describing chalcones and their derivatives on selected activities (e.g., anti-inflammatory, antimitotic, cytotoxic, antioxidant, anti-infection) is provided in this paper. Synthesis, combinatorial techniques, biological evaluation in vitro/in vivo, and new biological assays are discussed. In addition to selected biological data, a wide range of pharmaceutical applications and pharmaceutical compositions are also summarized.

EXPERT OPINION

Several natural and synthetic chalcones and their derivatives appear as promising anti-inflammatory and anticancer activities. Their clinical evaluation will be critical to assess their therapeutic utility. Those for which the mechanism of action is well defined can serve as lead compounds for the design of new, more promising molecules.

Trimethoxy-chalcone derivatives inhibit growth of Leishmania braziliensis: synthesis, biological evaluation, molecular modeling and structure-activity relationship (SAR)

In this work we described the synthesis, the antileishmanial activity and the molecular modeling and structure-activity relationship (SAR) evaluations of a series of chalcone derivatives. Among these compounds, the methoxychalcones 2h, 2i, 2j, 2k and 2l showed significant antileishmanial activity (IC(50)<10 μM). Interestingly 2i (IC(50)=2.7 μM), 2j (IC(50)=3.9 μM) and 2k (IC(50)=4.6 μM) derivatives presented better antileishmanial activity than the control drug pentamidine (IC(50)=6.0 μM). Our SAR study showed the importance of methoxy di-ortho substitution at phenyl ring A and the relationship between the frontier orbital HOMO coefficients distribution of these molecules and their activity. The most active compounds 2h, 2i, 2j, 2k, and 2l fulfilled the Lipinski rule-of-five which theoretically is important for good drug absorption and permeation through biological membranes. The potential profile of 2j (IC(50)=3.9 μM and CC(50)=216 μM) pointed this chalcone derivative as a hit compound to be further explored in antileishmanial drug design.

Chalcone-imidazolone conjugates induce apoptosis through DNA damage pathway by affecting telomeres

Background

Breast cancer is one of the most prevalent cancers in the world and more than one million women are diagnosed leading to 410,000 deaths every year. In our previous studies new chalcone-imidazolone conjugates were prepared and evaluated for their anticancer activity in a panel of 53 human tumor cell lines and the lead compounds identified were 6 and 8. This prompted us to investigate the mechanism of apoptotic event.

Results

Involvement of pro-apoptotic protein (Bax), active caspase-9 and cleavage of retinoblastoma protein was studied. Interestingly, the compounds caused upregulation of p21, check point proteins (Chk1, Chk2) and as well as their phosphorylated forms which are known to regulate the DNA damage pathway. Increased p53BP1 foci by immunolocalisation studies and TRF1 suggested the possible involvement of telomere and associated proteins in the apoptotic event. The telomeric protein such as TRF2 which is an important target for anticancer therapy against human breast cancer was extensively studied along with proteins involved in proper functioning of telomeres.

Conclusions

The apoptotic proteins such as Bax, active caspase-9 and cleaved RB are up-regulated in the compound treated cells revealing the apoptotic nature of the compounds. Down regulation of TRF2 and upregulation of the TRF1 as well as telomerase assay indicated the decrease in telomeric length revealing telomeric dysfunction and thereby controlling the rapid rate of cell proliferation. In summary, chalcone-imidazolone conjugates displayed significant DNA damage activity particularly at telomeres and caused both apoptosis and senescence-like growth arrest which suggested that these compounds have potential activity against breast carcinoma.

Recent advances in understanding the antibacterial properties of flavonoids

Antibiotic resistance is a major global problem and there is a pressing need to develop new therapeutic agents. Flavonoids are a family of plant-derived compounds with potentially exploitable activities, including direct antibacterial activity, synergism with antibiotics, and suppression of bacterial virulence. In this review, recent advances towards understanding these properties are described. Information is presented on the ten most potently antibacterial flavonoids as well as the five most synergistic flavonoid-antibiotic combinations tested in the last 6 years (identified from PubMed and ScienceDirect). Top of these respective lists are panduratin A, with minimum inhibitory concentrations (MICs) of 0.06-2.0 μg/mL against Staphylococcus aureus, and epicatechin gallate, which reduces oxacillin MICs as much as 512-fold. Research seeking to improve such activity and understand structure-activity relationships is discussed. Proposed mechanisms of action are also discussed. In addition to direct and synergistic activities, flavonoids inhibit a number of bacterial virulence factors, including quorum-sensing signal receptors, enzymes and toxins. Evidence of these molecular effects at the cellular level include in vitro inhibition of biofilm formation, inhibition of bacterial attachment to host ligands, and neutralisation of toxicity towards cultured human cells. In vivo evidence of disruption of bacterial pathogenesis includes demonstrated efficacy against Helicobacter pylori infection and S. aureus α-toxin intoxication.

Up-regulation of licochalcone A biosynthesis and secretion by Tween 80 in hairy root cultures of Glycyrrhiza uralensis Fisch

We evaluated the effect of Tween 80 as elicitor on licochalcone A from hairy root cultures of Glycyrrhiza uralensis Fisch. After a 15-days treatment with 2% Tween 80, hairy roots still grew well and produced higher levels of licochalcone A and total flavonoids than the control (without treatment). Licochalcone A content and total flavonoid content were 3.103 and 127.095 mg per flask (9- and 11-fold higher), respectively, compared with controls. Secretion of licochalcone A and total flavonoids into the culture medium was remarkably high, up to 98 and 94% of the total production, respectively. The enhanced flavonoid production was associated with elevated mRNA levels and enzyme activities of phenylalanine ammonia-lyase (PAL), 4-coumarate:coenzyme A ligase (4CL), and cinnamate-4-hydroxylase (C4H). These results clearly demonstrated that Tween 80 treatment permeabilized the roots to enhance secretion, but also acted as an efficient elicitor of licochalcone A and total flavonoid production in hairy roots of G. uralensis Fisch.

Improved small-molecule macroarray platform for the rapid synthesis and discovery of antibacterial chalcones

Bacterial resistance to current antibiotics is a major global health threat. Consequently, there is an urgent need for the identification of new antibacterial agents. We are applying the small-molecule macroarray platform to rapidly synthesize and screen compounds for activity against methicillin-resistant Staphylococcus aureus (MRSA). Herein, we report the synthesis of a 1,3-diphenyl-2-propen-1-one (chalcone) macroarray using a Rink-amide linker-derivatized cellulose support. The Rink linker allowed for the incorporation of a broader array of library building blocks relative to our previous syntheses because milder reaction conditions could be utilized; significantly higher compound loadings were also achieved (~80% vs ~15%). Analysis of the 174-member chalcone macroarray in off-support antibacterial screening assays revealed three chalcones with minimum inhibitory concentration (MIC) values against MRSA comparable to currently used antibacterial drugs and low hemolytic activities. These results serve to further showcase and extend the utility of the small molecule macroarray for antibacterial discovery.

Synthesis and in vitro evaluation of novel coumarin-chalcone hybrids as potential anticancer agents

A series of coumarin-chalcone hybrids have been synthesized and evaluated for their in vitro cytotoxicity against a panel of four human cancer cell lines and normal fibroblasts (NIH3T3). Among 21 compounds screened, three compounds (23, 25 and 26) showed IC(50) range from 3.59 to 8.12 μM. The most promising compound 26 showed around 30-fold more selectivity towards C33A (cervical carcinoma) cells over normal fibroblast NIH3T3 cells with an IC(50) value of 3.59 μM.

(E)-1-(4-Amino-phen-yl)-3-(2,4,5-trimeth-oxy-phen-yl)prop-2-en-1-one

Mol­ecules of the title amino­chalcone, C₁₈H₁₉NO₄, are twisted, with a dihedral angle of 11.26 (6)° between the 4-amino­phenyl and 2,4,5-trimeth­oxy­phenyl rings. The conformations of the three meth­oxy groups with respect to the benzene ring are slightly different. Two meth­oxy groups are almost coplanar with the attached benzene ring [C—O—C—C torsion angles of −1.45 (19) and 1.5 (2)°], while the third is (−)-synclinal with the attached benzene ring [C—O—C—C = −81.36 (17)°]. In the crystal structure, mol­ecules are stacked into columns along the b axis and mol­ecules in adjacent columns are linked by N—H⋯O hydrogen bonds into V-shaped double columns. Weak π–π inter­actions are also observed, with a centroid-centroid distance of 3.7532 (8) Å.

Synthesis and anti-cancer activity of chalcone linked imidazolones

A series of novel chalcone linked imidazolones were prepared and evaluated for their anti-cancer activity against a panel of 53 human tumour cell lines derived from nine different cancer types: leukemia, lung, colon, CNS, melanoma, ovarian, renal, prostate and breast. Some of these hybrids (6, 7 and 8) showed good anti-cancer activity with GI(50) values ranging from 1.26 to 13.9 microM. When breast carcinoma cells (MCF-7) were treated with 10 microM concentration of compounds TMAC, CA-4, 6 and 8 cell cycle arrest was observed in G2/M phase. Surprisingly, the increased concentration of the same compound to 30 microM caused accumulation of cells in G0/G1 phase of the cell cycle.

Screening of biological activities of a series of chalcone derivatives against human pathogenic microorganisms

In an effort to develop new antimicrobial agents, a series of chalcone derivatives, 3-60, were prepared by Claisen-Schmidt condensation of appropriate acetophenones and 2-furyl methyl ketones with appropriate aromatic aldehydes, furfural, and thiophene-2-carbaldehyde in an aqueous solution of NaOH and EtOH at room temperature. The synthesized compounds were characterized by means of their IR- and NMR-spectral data, and elemental analysis. All compounds were tested for their antibacterial and antifungal activities by the disc diffusion method. For the most active compounds, also minimum inhibitory concentrations (MICs) were determined.

Comparison of the antiplasmodial and falcipain-2 inhibitory activity of beta-amino alcohol thiolactone-chalcone and isatin-chalcone hybrids

The synthesis and biological evaluation of two novel series of natural-product-like hybrids based on the chalcone, thiolactone and isatin scaffolds is herein described. Results for a 36-member beta-amino alcohol triazole library showed that the thiolactone-chalcones, with IC(50)s ranging from 0.68 to 6.08 microM, were more active against W2 strain Plasmodium falciparum than the isatin-chalcones with IC(50)s of 14.9 microM or less. Also of interest is falcipain-2 inhibitory activity displayed by the latter, whereas the thiolactone-chalcones lacked enzyme inhibitory activity.