Carbon-13 NMR signals of some natural coumarins and their derivatives

The ¹³C NMR spectra of the natural coumarins ostruthin, osthol, aegelinol (enantiomer of decursinol), luvangetin, seselin, anomalin, oxypeucedanin (and its enantiomer prangolarin) and oxypeucedanin hydrate and some of their derivatives have been studied. Self-consistent resonance assignments have been made following chemical shift theory and using simple models. Carbon-hydrogen coupling constants of some compounds are also reported. The alkoxy group/s at C-5 and/or C-8 in linear furocoumarins, as well as in linear pyranocoumarins, have unusually small shielding effects on the ortho- and para-carbons. This study also indicates that the C-4a and C-8 resonance assignments of osthol, made earlier, should be reversed.     

Long‐Lived Radical Cation Salts Obtained by Interaction of Monocyclic Arenes with Niobium and Tantalum Pentahalides at Room Temperature: EPR and DFT Studies

The 1:3 reactions of the alkoxy arenes 1,4‐(MeO)₂C₆H₄ and 1,4‐F₂‐2,5‐(MeO)₂C₆H₂ with TaF₅ in chloroform at 40–50 °C resulted in formation in about 35 % yield of the long‐lived radical cation salts [1,4‐(MeO)₂C₆H₄][Ta₂F₁₁] ( 2 a ) and [1,4‐F₂‐2,5‐(MeO)₂C₆H₂][Ta₂F₁₁] ( 2 b ), respectively. The non‐alkoxy‐substituted [arene][M₂X₁₁] [M=Ta, X=F: arene=C₆H₅Me ( 2 c ), 1,4‐C₆H₄Me₂ ( 2 d ), C₆H₅F ( 2 e ), C₆H₅NO₂ ( 2 f ); M=Nb, X=F: arene=C₆H₅Me ( 4 a ), 1,4‐C₆H₄Me₂ ( 4 b ), C₆H₅F ( 4 c ), C₆H₅NO₂ ( 4 d ); M=Ta, X=Cl: arene=1,4‐C₆H₄Me₂ ( 5 )] were obtained from the 3:1 reactions of MX₅ with the appropriate arene in chloroform at temperatures in the range 40–90 °C. Compounds 2 – 5 were detected by EPR spectroscopy (in CHCl₃) at room temperature, and their gas‐phase structures were optimized by DFT calculations. Formation of the M^IV species [MX₄(NCMe)₂] [M=Ta, X=F ( 3 a ); M=Nb, X=F ( 3 b ); M=Ta, X=Cl ( 3 c )] was ascertained by EPR spectroscopy on solutions obtained by treatment of the reaction mixtures with acetonitrile. Non‐selective reactions occurred upon combination of 1,4‐F₂‐2,5‐(MeO)₂C₆H₂ with AgNbF₆ (in CH₂Cl₂) and 1,4‐(MeO)₂C₆H₄ with SbF₅.     

Novel Anti-Melanogenic Compounds, (Z)-5-(Substituted Benzylidene)-4-thioxothiazolidin-2-one Derivatives: In Vitro and In Silico Insights

To confirm that the β-phenyl-α,β-unsaturated thiocarbonyl (PUSTC) scaffold, similar to the β-phenyl-α,β-unsaturated carbonyl (PUSC) scaffold, acts as a core inhibitory structure for tyrosinase, twelve (Z)-5-(substituted benzylidene)-4-thioxothiazolidin-2-one ((Z)-BTTZ) derivatives were designed and synthesized. Seven of the twelve derivatives showed stronger inhibitory activity than kojic acid against mushroom tyrosinase. Compound 2b (IC₅₀ = 0.47 ± 0.97 µM) exerted a 141-fold higher inhibitory potency than kojic acid. Kinetic studies’ results confirmed that compounds 2b and 2f are competitive tyrosinase inhibitors, which was supported by high binding affinities with the active site of tyrosinase by docking simulation. Docking results using a human tyrosinase homology model indicated that 2b and 2f might potently inhibit human tyrosinase. In vitro assays of 2b and 2f were conducted using B16F10 melanoma cells. Compounds 2b and 2f significantly and concentration-dependently inhibited intracellular melanin contents, and the anti-melanogenic effects of 2b at 10 µM and 2f at 25 µM were considerably greater than the inhibitory effect of kojic acid at 25 µM. Compounds 2b and 2f similarly inhibited cellular tyrosinase activity and melanin contents, indicating that the anti-melanogenic effects of both were due to tyrosinase inhibition. A strong binding affinity with the active site of tyrosinase and potent inhibitions of mushroom tyrosinase, cellular tyrosinase activity, and melanin generation in B16F10 cells indicates the PUSTC scaffold offers an attractive platform for the development of novel tyrosinase inhibitors.     

ACTIVATION OF THE HUMAN IMMUNODEFICIENCY VIRUS PROMOTER BY UVA RADIATION IN COMBINATION WITH PSORALENS OR ANGELICINS

Abstract— The effects of mono- and bifunctional furocoumarins plus UVA radiation (PUVA and related treatments) on the human immunodeficiency virus-1 (HIV-1) promoter were studied using HeLa cells stably transfected with the chloramphenicol acetyl transferase gene under the control of the HIV-1 promoter. The experiments were performed with three psoralens (5-methoxypsoralen, 5-MOP; 8-methoxypsoralen, 8-MOP; and 4′-aminomethyl-4,8,5′-trimethyl-psoralen, AMT) and four angelicins (angelicin; 4,5′-diniethylangclicin, 4,5′-DMA; 6,4′-dimethylangelicin, 6,4′-DMA; and 4,6,4′-trimethylangelicin, TMA). The drugs alone and UVA radiation alone showed no erect on the HIV promoter. However, when the cells were incubated with the furocoumarins at 0.1–40 μg/mL and then irradiated. the HIV promoter was activated in distinct fluence ranges, i.e. (1) no promoter activity was discernible at low fluences (e.g. at 0.1 μg/mL of 8-MOP up to 100 kJ/m²), (2) as the fluence was increased, the promoter activity increased to reach a maximum (10–50-fold with respect to the unexposcd samples), and (3) as the fluence was further increased, the promoter activity decreased. Similar (although shifted on the fluence scale) pattcrns were observed with either > 340-nm UVA radiation or with UVA radiation contaminated with a small amount of UVB radiation (typical for PUVA lamps). The effective fluences were inversely related to the drug concentration. Experiments with 5-MOP and 8-MOP indicated reciprocity of the drug concentration and radiation hence. The HIV promoter response patterns were similar for monofunctional angelicins and bifunctional psoralens. This indicated that the furocoumarin-DNA crosslinks are not a prerequisite for the promoter activation and that the monoadducts suffice to elicit the HIV promoter response. The HIV promoter-activating effectiveness of diKcrent drugs correlated with their photosensitizing potential. Thus, among psoralens the effectiveness order was AMT >. 5-MOP >8-MOP, and among angelicins: TMA > 6,4′-DMA > 4,5′-DMA > angelicin. The ektiveness did not vary substantially for 5-MOP, 8-MOP, 4,5′-DMA, and 6,4′-DMA. The combined drug and UVA radiation doses were higher than those that elicit cellular responses or those that may be received by the human white blood cells during cxtracorporeal PUVA therapy (photopheresis).     

ATR/Chk1 Pathway is Activated by Oxidative Stress in Response to UVA Light in Human Xeroderma Pigmentosum Variant Cells

The crucial role of DNA polymerase eta in protecting against sunlight‐induced tumors is evidenced in Xeroderma Pigmentosum Variant (XP‐V) patients, who carry mutations in this protein and present increased frequency of skin cancer. XP‐V cellular phenotypes may be aggravated if proteins of DNA damage response (DDR) pathway are blocked, as widely demonstrated by experiments with UVC light and caffeine. However, little is known about the participation of DDR in XP‐V cells exposed to UVA light, the wavelengths patients are mostly exposed. Here, we demonstrate the participation of ATR kinase in protecting XP‐V cells after receiving low UVA doses using a specific inhibitor, with a remarkable increase in sensitivity and γH2AX signaling. Corroborating ATR participation in UVA‐DDR, a significant increase in Chk1 protein phosphorylation, as well as S‐phase cell cycle arrest, is also observed. Moreover, the participation of oxidative stress is supported by the antioxidant action of N‐acetylcysteine (NAC), which significantly protects XP‐V cells from UVA light, even in the presence of the ATR inhibitor. These findings indicate that the ATR/Chk1 pathway is activated to control UVA‐induced oxidatively generated DNA damage and emphasizes the role of ATR kinase as a mediator of genomic stability in pol eta defective cells.     

In Vitro and in Vivo Anticancer Activity of Sophorolipids to Human Cervical Cancer

Six characteristic di-acetylated lactonic sophorolipids with C16:1, C16:0, C18:0, C18:1, C18:2, and C18:3 fatty acid were obtained from Starmerella bombicola CGMCC 1576. In order to confirm their anticancer activity against human cervical cancer cells and reveal the structure-activity relationships, their anti-proliferation effects on HeLa and CaSki cells were estimated. The cytotoxicity of sophorolipid molecules with different degrees of unsaturation was proved to be influenced by carbon chain length of sophorolipids. The longer the carbon chain length, the stronger the cytotoxicity of sophorolipids. The inhibitory mechanism of a di-acetylated lactonic C18:1 sophorolipid on HeLa cells was investigated. The cells developed many features of apoptosis and cell cycle was blocked at G₀ phase and partly at G₂ phase. The expression of CHOP and Bip/GRP78 was induced. Caspase-12 and caspase-3 were both activated. However, mitochondrial membrane potential and concentration of cytosolic cytochrome C did not change. The induced apoptosis of HeLa cells was probably triggered through endoplasmic reticulum signaling pathway without involvement of mitochondria. In vivo, 5, 50, and 500 mg/kg lactonic sophorolipids showed 29.90, 41.24, and 52.06 % of inhibition without significant toxicity to tumor-bearing mice, respectively. Our findings may suggest a potential use of sophorolipids in human cervical cancer treatment.     

Polymerization and copolymerization of functionalized 2‐alkoxy‐1‐methylenecyclopropanes to form new polymers having alkoxy substituents

The polymers with functionalized alkoxy groups and with narrow molecular weight distribution (M_w/M_n < 1.12) are obtained from the living polymerization of 2‐alkoxy‐1‐methylenecyclopropanes using π‐allylpalladium complex, [(PhC₃H₄)Pd(μ‐Cl)]₂, as the initiator. The polymers with oligoethylene glycol groups in the alkoxy substituent are soluble in water, and hydroboration of the C?C double bond and ensuing addition of the OH groups to C?N bond of alkyl isocyanate produce the polymers with urethane pendant groups. The reaction decreases solubility of the polymer in water significantly. Di‐ and triblock copolymers of the 2‐alkoxy‐1‐methylenecyclopropanes are prepared by consecutive addition of the two or three 2‐alkoxy‐1‐methylenecyclopropane monomers to the Pd initiator. The polymers which contain both hydrophobic butoxy or tert‐butoxy group and hydrophilic oligoethylene glycol group dissolve in water and/or organic solvents, depending on the substituents. The ¹H NMR spectrum of poly( 1a ‐b‐ 1h ) (? (CH₂C(?CH₂)CHOBu)_n? (CH₂C(?CH₂)CH(OCH₂CH₂)₃OMe)_m? ) in D₂O solution exhibits peaks because of the butoxy and ?CH₂ hydrogen in decreased intensity, indicating that the polymer forms micelle particles containing the hydrophilic segments in their external parts. Aqueous solution of the polymer with a small amount of DPH (DPH = 1,6‐diphenyl‐1,3,5‐hexatriene) shows the absorbance due to DPH at concentration of the polymer higher than 5.82 × 10^?5 g mL^?1. Other block copolymers such as poly( 1b ‐b‐ 1h ) and poly( 1a ‐b‐ 1g ) also form the micelles that contain DPH in their core. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 959–972, 2009     

Side‐chain conformations in the isomorphous polyfluorinated {4,4′‐bis[(2,2‐difluoroethoxy)methyl]‐2,2′‐bipyridine‐κ2N,N′}dichloridopalladium and ‐platinum complexes

The polyfluorinated title compounds, [M Cl₂(C₁₆H₁₆F₄N₂O₂)] or [4,4′‐(HCF₂CH₂OCH₂)₂‐2,2′‐bpy]M Cl₂ [M = Pd, ( 1 ), and M = Pt, ( 2 )], have –C(H_α)₂OC(H_β)₂CF₂H side chains with H‐atom donors at the α and β sites. The structures of ( 1 ) and ( 2 ) are isomorphous, with the nearly planar (bpy)M Cl₂ molecules stacked in columns. Within one column, π‐dimer pairs alternate between a π‐dimer pair reinforced with C—H…Cl hydrogen bonds (α,α) and a π‐dimer pair reinforced with C—H_β…F(—C) interactions (abbreviated as C—H_β…F—C,C—H_β…F—C). The compounds [4,4′‐(CF₃CH₂OCH₂)₂‐2,2′‐bpy]M Cl₂ [M = Pd, ( 3 ), and M = Pt, ( 4 )] have been reported to be isomorphous [Lu et al. (2012). J. Fluorine Chem. 137 , 54–56], yet with disorder in the fluorous regions. The molecules of ( 3 ) [or ( 4 )] also form similar stacks, but with alternating π‐dimer pairs between the (α,β; α,β) and (β,β) forms. Through (C—)H…Cl hydrogen‐bond interactions, one molecule of ( 1 ) [or ( 2 )] is expanded into an aggregate of two inversion‐related π‐dimer pairs, one pair in the (α,α) form and the other pair in the (C—H_β…F—C,C—H_β…F—C) form, with the plane normals making an interplanar angle of 58.24 (3)°. Due to the demands of maintaining a high coordination number around the metal‐bound Cl atoms in molecule ( 1 ) [or ( 2 )], the ponytails of molecule ( 1 ) [or ( 2 )] bend outward; in contrast, the ponytails of molecule ( 3 ) [or ( 4 )] bend inward.     

Synthesis and Biological Activity of Some New Pyrazole Copper(II) Complexes

As a part of systematic investigation of synthesis and biologically active compounds of pyrazole derivatives containing transition metal, several new pyrazole copper(II) complexes 3a?f were synthesized from pyrazole sodium salts 2a?f , which were produced from spiro‐pyrazoles 1a?f and sodium hydride by a ring‐opening reaction. All the synthesized compounds were characterized by spectroscopic analysis. Pyrazole copper(II) complexes 3a?d and 3f exhibited high DNA cleavage activity in vitro. Furthermore, compounds 3a?f were tested for their growth inhibitory activity in A549 lung cancer, B16F10 murine melanoma, and HeLa human uterine carcinoma cells. Compounds 3c,d displayed moderate B16F10 and HeLa inhibitory activity levels ( 3c : IC₅₀ = 45 μM in B16F10 cells and 34 μM in HeLa cells, 3d : IC₅₀ = 50 μM in B16F10 cells and 32 μM in HeLa cells).     

Repair of furocoumarin-plus-UVA-induced damage and mutagenic consequences in eukaryotic cells

In the presence of near-UV radiation (UVA) furocoumarins (psoralens) photoinduce defined lesions in DNA, i.e. monoadducts and interstrand crosslinks. Their use in photochemotherapy (psoralen plus UVA (PUVA) treatment) and cosmetics raises questions concerning the repairability of these lesions and their genotoxic consequences. We have analysed the repair of psoralen photoadducts in cultured eukaryotic cells, such as yeast and mammalian cells, for furocoumarins of photochemotherapeutic interest. In yeast, the interaction of repair pathways differs in exogenous (plasmid) and endogenous (chromosomal) DNA. The order of mutagenic activity is 4,5',8-trimethylpsoralen greater than 5-methoxypsoralen greater than 8-methoxypsoralen greater than 7-methylpyrido[3,4-c]psoralen greater than 3-carbethoxypsoralen. The mutagenicity is dependent on psoralen functionality, concentration and bioavailability, maximal UVA dose, wavelength, dose (fluence) rate and presence or absence of chemical filters. It probably involves an inducible component. Chromosome breakage occurs during the repair period after PUVA treatment. It appears that the genotoxic effects of psoralens are produced by a specific arrangement of induced photolesions and the interaction of different repair systems.     

Unexpected beauty and diversity in the structures of three homologous 4,5‐dialkoxy‐1‐ethynyl‐2‐nitrobenzenes: the subtle interplay between intermolecular C—H…O hydrogen bonds and alkyl chain length

The synthesis, ¹H and ¹³C NMR spectra, and X‐ray structures are described for three dialkoxy ethynylnitrobenzenes that differ only in the length of the alkoxy chain, namely 1‐ethynyl‐2‐nitro‐4,5‐dipropoxybenzene, C₁₄H₁₇NO₄, 1,2‐dibutoxy‐4‐ethynyl‐5‐nitrobenzene, C₁₆H₂₁NO₄, and 1‐ethynyl‐2‐nitro‐4,5‐dipentoxybenzene, C₁₈H₂₅NO₄. Despite the subtle changes in molecular structure, the crystal structures of the three compounds display great diversity. Thus, 1‐ethynyl‐2‐nitro‐4,5‐dipropoxybenzene crystallizes in the trigonal crystal system in the space group , with Z = 18, 1,2‐dibutoxy‐4‐ethynyl‐5‐nitrobenzene crystallizes in the monoclinic crystal system in the space group P 2₁/c , with Z = 4, and 1‐ethynyl‐2‐nitro‐4,5‐dipentoxybenzene crystallizes in the triclinic crystal system in the space group , with Z = 2. The crystal structure of 1‐ethynyl‐2‐nitro‐4,5‐dipropoxybenzene is dominated by planar hexamers formed by a bifurcated alkoxy sp‐C—H…O,O′ interaction, while the structure of the dibutoxy analogue is dominated by planar ribbons of molecules linked by a similar bifurcated alkoxy sp‐C—H…O,O′ interaction. In contrast, the dipentoxy analogue forms ribbons of molecules alternately connected by a self‐complementary sp‐C—H…O₂N interaction and a self‐complementary sp²‐C—H…O₂N interaction. Disordered solvent was included in the crystals of 1‐ethynyl‐2‐nitro‐4,5‐dipropoxybenzene and its contribution was removed during refinement.     

Synthesis and characterisation of asymmetrical mesogenic materials based on 2,5-disubstituted-1,3,4-oxadiazole

New mesogenic homologous series bearing 1,3,4-oxadiazole ring with a nitro terminal group, 4-(5-(4-nitrophenyl)-1,3,4-oxadiazol-2-yl)phenyl 4-((4-methoxybenzylidene)amino)benzoate (G₁–G₁₁), were synthesised. Their chemical structures are identified by fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (¹H-NMR) and elemental analysis. The liquid crystalline properties of the series G_n and their precursory F_n were screened by differential scanning calorimetry and optical polarising microscopy (OPM). The compounds of the series G_n were screened by thermogravimetric analysis to observe their thermal stability. The target compounds (G_n) in this study, were displayed different liquid crystalline mesophase, the first two homologous (G₁ and G₂) did not show any liquid crystalline behaviour, the homologous (G₃–G₁₀) which have an alkoxy terminal group (n = 3–10) exhibited nematic phase, whilst the last derivative of the series (G₁₁), n = 12, displayed SmA phase. The mesomorphic properties of these derivatives were affected by the presence of the nitro group at the end of the molecules which was classified as a strong polar group. Also, the role of alkoxy terminal chain and the bent heterocyclic ring (1,3,4-oxadiazole) in the liquid crystalline properties of these molecules were debated.     

Ambient UVA‐Induced Expression of p53 and Apoptosis in Human Skin Melanoma A375 Cell Line by Quinine

This study aimed to analyze the phototoxic mechanism and photostability of quinine in human skin cell line A375 under ambient intensities of UVA (320–400 nm). Photosensitized quinine produced a photoproduct 6‐methoxy‐quinoline‐4‐ylmethyl‐oxonium identified through LC‐MS/MS. Generation of ¹O₂, O₂^??, and ^?OH was measured and further substantiated through their respective quenchers. Photosensitized Quinine (Q) caused degradation of 2‐deoxyguanosine, the most sensitive nucleotide to UV radiation. The intracellular ROS was increased in a concentration‐dependent manner. Significant reduction in metabolic status measured in terms of cell viability (54%) at 25 μg mL^?1 was observed through MTT assay. Results of MTT assay accord NRU assay. Single strand DNA breaks and apoptosis were increased significantly (P < 0.01) as observed through comet assay and EB/AO double staining. Photosensitized quinine caused cells to arrest in G₂ phase of cell cycle and induced apoptosis (5.08%) as revealed through FACS. Real‐Time PCR showed upregulation of p21 (4.56 folds) and p53 (2.811 folds) genes expression. Thus, our study suggests that generation of reactive oxygen species by quinine under ambient intensity of UVA may result into deleterious phototoxic effects among human population.     

The synthesis and liquid crystalline behaviour of alkoxy‐substituted derivatives of 1,4‐bis(phenylethynyl)benzene

Despite the prevalence of organised 1,4‐bis(phenylethynyl)benzene derivatives in molecular electronics, the interest in the photophysics of these systems and the common occurrence of phenylethynyl moeties in molecules that exhibit liquid crystalline phases, the phase behaviour of simple alkoxy‐substituted 1,4‐bis(phenylethynyl)benzene derivatives has not yet been described. Two series of 1,4‐bis(phenylethynyl)benzene derivatives, i.e. 1‐[(4′‐alkoxy)phenylethynyl]‐4‐(phenylethynyl)benzenes (5a–5f) and methyl 4‐[(4″‐alkoxy)phenylethynyl‐4′‐(phenylethynyl)] benzoates (18a–18f) [alkoxy = n‐C₄H₉ (a), n‐C₆H₁₃ (b), n‐C₉H₁₉ (c), n‐C₁₂H₂₅ (d), n‐C₁₄H₂₉ (e), n‐C₁₆H₃₃ (f)] have been prepared and characterised. Both series have good chemical stability at temperatures up to 210°C, the derivatives featuring the methyl ester head‐group (18a–18f) offering rather higher melting points and generally stabilising a more diverse range of mesophases at higher temperatures than those found for the simpler compounds (5a–5f). Smectic phases are stabilised by the longer alkoxy substituents, whereas for short and intermediate chain lengths of the simpler system (5a–5c) nematic phases dominate. Diffraction analysis was used to identify the SmB_hex phase in (5d–5f) that is stable within a temperature range of approximately 120–140°C. The relationships between the organisation of molecules within these moderate temperature liquid crystalline phases and other self‐organised states (e.g. Langmuir‐Blodgett films) remain to be explored.     

The Effects of Microenvironment Polarity and Dendritic Branching of Aliphatic Hydrocarbon Dendrons on the Self‐Assembly of 2‐Ureido‐4‐pyrimidinones

Two series of aliphatic hydrocarbon‐based G1–G3 dendritic 2‐ureido‐4‐pyrimidinones (UPy) ( S‐Gn )₂ and ( L‐Gn )₂, differing from one another by the distance between the branching juncture to the urea end, were prepared and characterized. These hydrocarbon dendrons were also appended to a p‐aminonitrobenzene solvatochromic chromophore in order to probe their microenvironment polarity. While positive solvatochromism was observed which indicated the chromophore was solvent accessible, there was no significant difference between the microenvironment polarities on going from the G1 to the G3 dendrons. The self‐assembling behavior and tautomeric preference of the dendritic UPy derviatives were examined by ¹H NMR spectroscopy. The dimerization constants (K_dim*) of the DDAA tautomers were unchanged at 10⁷ M ^?1 in CDCl₃ at both 25 and 50 °C, which were comparable to those of UPy compounds bearing other nonpolar substitutents. Furthermore, the lower limits on the K′_dim* of the DADA tautomeric forms of the ( S‐Gn )₂ and ( L‐Gn )₂ series were determined to be 10⁶ and 10⁵ M ^?1 in CDCl₃, respectively. It was found that a closer proximity of the dendron branching juncture to the UPy unit could lead to a destabilization effect on the dimeric states. Hence, the ( L‐Gn )₂ dimers are more stable than those of ( S‐Gn )₂ in the DDAA form, but the latter are more stable than the former in the tautomeric DADA state. This study showed that both the highly nonpolar microenvironment and the proximity of the dendritic branching juncture to the UPy motif could alter the strength and profile of the hydrogen bond‐mediated self‐assembling process.     

Synthesis and biological activities of some new thiazolidine derivatives containing pyrazole ring system

As a part of systematic investigation of synthesis and biologically active compounds of thiazolidine (TZD) derivatives containing pyrazole ring system, several new pyrazole–TZD derivatives 8a , 8b , 8c , 8d and 9a , 9b , 9c , 9d have been synthesized. Compounds 8a , 8b , 8c , 8d were prepared from N‐substituted TZDs 6a , 6b , 6c , 6d and 1H‐pyrazole‐4‐carboxaldehyde 7 by Knoevenagel‐type reaction. Treatment of 8a , 8b , 8c , 8d with sodium hydride at room temperature caused dimerization reaction to afford the corresponding spirocompounds 9a , 9b , 9c , 9d . All the synthesized compounds were characterized by spectroscopic analysis. In vitro, the synthesized compounds 8a , 8b , 8c , 8d and 9a , 9b , 9c , 9d were tested for their growth inhibitory activity in A549 lung cancer, B16F10 murine melanoma, and HeLa human uterine carcinoma cells and for their differentiation of 3T3‐L1 preadipocytes to adipocytes. The results showed that compound 8c possessed growth inhibitory effect of B16F10 cells (IC₅₀ = 27 μM) and compounds 9c , 9d had induction effect on the differentiation of 3T3‐L1 preadipocytes. J. Heterocyclic Chem., (2011).     

Discovery of a more potent anticancer agent than C4-benzazole 1,8-naphthalimide derivatives against murine melanoma

Three novel naphthalimide-based derivatives were synthesized and tested in vitro as anticancer agents. Our previous report of the C4-benzazole 1,8-naphthalimide derivatives showed good inhibition against murine melanoma. We aimed to synthesize more potent agents and found that compound 5 reported in this article behaved 5- to 10-fold potency than our previous best results. The unique structure of compound 5 consisted of a naphthalimide framework in which C4 position was linked with an ethylenediamine group where the amino group was coupled with a 2-piconic acid moiety. Compound 5 exhibited the most potent inhibitory activity toward human DNA topoisomerase II proteins with IC₅₀ value (2.6 ± 0.1 μM) against murine B16F10 melanoma cells among the three target compounds synthesized in this study. In accordance with this finding, the results of molecular docking also revealed that compound 5 has the highest affinity with human DNA topoisomerase II among the selected compounds. Compound 5 , therefore, has high potential for becoming a lead compound.     

The Autophagy Receptor Adaptor p62 is Up‐regulated by UVA Radiation in Melanocytes and in Melanoma Cells

UVA (315–400 nm) is the most abundant form of UV radiation in sunlight and indoor tanning beds. However, much remains to be understood about the regulation of the UVA damage response in melanocytes and melanoma. Here, we show that UVA , but not the shorter waveband UVB (280–315 nm), up‐regulates adaptor protein p62 in an Nrf2‐ and reactive oxygen species (ROS )‐dependent manner, suggesting a UVA ‐specific effect on p62 regulation. UVA ‐induced p62 up‐regulation was inhibited by a mitochondria‐targeted antioxidant or Nrf2 knockdown. In addition, p62 knockdown inhibited UVA ‐induced ROS production and Nrf2 up‐regulation. We also report here a novel regulatory feedback loop between p62 and PTEN in melanoma cells. PTEN overexpression reduced p62 protein levels, and p62 knockdown increased PTEN protein levels. As compared with normal human skin, p62 was up‐regulated in human nevus, malignant melanoma and metastatic melanoma. Furthermore, p62 was up‐regulated in melanoma cells relative to normal human epidermal melanocytes, independent of their BRAF or NRAS mutation status. Our results demonstrated that UVA up‐regulates p62 and induces a p62‐Nrf2 positive feedback loop to counteract oxidative stress. Additionally, p62 forms a feedback loop with PTEN in melanoma cells, suggesting p62 functions as an oncogene in UVA ‐associated melanoma development and progression.     

In Silico Approach Using Free Software to Optimize the Antiproliferative Activity and Predict the Potential Mechanism of Action of Pyrrolizine-Based Schiff Bases

In the current study, a simple in silico approach using free software was used with the experimental studies to optimize the antiproliferative activity and predict the potential mechanism of action of pyrrolizine-based Schiff bases. A compound library of 288 Schiff bases was designed based on compound 10, and a pharmacophore search was performed. Structural analysis of the top scoring hits and a docking study were used to select the best derivatives for the synthesis. Chemical synthesis and structural elucidation of compounds 16a–h were discussed. The antiproliferative activity of 16a–h was evaluated against three cancer (MCF7, A2780 and HT29, IC₅₀ = 0.01–40.50 μM) and one normal MRC5 (IC₅₀ = 1.27–24.06 μM) cell lines using the MTT assay. The results revealed the highest antiproliferative activity against MCF7 cells for 16g (IC₅₀ = 0.01 μM) with an exceptionally high selectivity index of (SI = 578). Cell cycle analysis of MCF7 cells treated with compound 16g revealed a cell cycle arrest at the G₂/M phase. In addition, compound 16g induced a dose-dependent increase in apoptotic events in MCF7 cells compared to the control. In silico target prediction of compound 16g showed six potential targets that could mediate these activities. Molecular docking analysis of compound 16g revealed high binding affinities toward COX-2, MAP P38α, EGFR, and CDK2. The results of the MD simulation revealed low RMSD values and high negative binding free energies for the two complexes formed between compound 16g with EGFR, and CDK2, while COX-2 was in the third order. These results highlighted a great potentiality for 16g to inhibit both CDK2 and EGFR. Taken together, the results mentioned above highlighted compound 16g as a potential anticancer agent.