Synthesis and Antifungal Activity of 2‐Hydroxy‐4,5‐methylenedioxyaryl Ketones as Analogues of Kakuol

In a study aiming to determine the structural elements essential to the antifungal activity of kakuol, we synthesized a series of 2‐hydroxy‐4,5‐methylenedioxyaryl ketones, and we assayed their in vitro antifungal activity. The most sensitive target organisms to the action of these class of compounds were Phytophthora infestans, Phytium ultimum, Cercospora beticola, Cladosporium cucumerinum, and Rhizoctonia solani. Most of the analogs showed a remarkable in vitro activity, and some of them appeared significantly more effective than the natural product. The biological activity was mainly affected by introducing structural modification on the carbonyl moiety of the natural‐product molecule. In particular, compound 5a , bearing a C?C bond conjugated to the C?O group, was found active with a MIC value of 10 μg ml^?1 against Cladosporium cucumerinum. The results suggest that 2‐hydroxy‐4,5‐methylenedioxyaryl ketones can be considered promising candidates in the development of new antifungal compounds.     

Topoisomerase I‐Mediated Antiproliferative Activity of 10‐Substituted and 12‐Substituted Homocamptothecins

Homocamptothecin (hCPT) is an E‐ring modified camptothecin (CPT) analogue, which showed pronounced inhibitory activity of topoisomerase I. In search of novel hCPT‐type anticancer agents, two series of hCPT derivatives were synthesized and evaluated in vitro against three human tumor cell lines. The results indicated that the 10‐substituted hCPT derivatives had a considerably higher cytotoxic activity than the 12‐substituted ones. Among the 10‐substituted compounds, 8a, 8b, 9b , and 9i showed an equivalent or even more potent activity than the positive control drug topotecan against the lung cancer cell line A‐549. Moreover, the hCPT analogues 8a and 8b exhibited a higher topoisomerase I inhibitory activity than CPT at a concentration of 100 μM .     

Studies on Chemical Structure Modification and Structure?Activity Relationship of Derivatives of Gambogic Acid at C(39)

The natural product gambogic acid exhibits high potency in inhibiting cancer cell lines. Rational medicinal modifications on gambogic acid will improve its physicochemical properties and drug‐like characters. To investigate the structure? activity relationship of gambogic acid and also to find rational modification position on its chemical skeleton, we designed, synthesized, and characterized 16 derivatives of gambogic acid that were modified at C(39). The structure? activity relationships (SARs) were discussed. The anti‐proliferation data were accquired through MTT (=3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl‐2H‐tetrazolium bromide) assays of A549, BGC823, U251, HepG2, and MDA‐MB‐231 cancer cell lines. Most of the synthesized compounds showed strong inhibitory effects. The SAR study revealed that derivatives with aliphatic amino moieties at C(39) were more potent than those with other substituents. The C(39) position can undergo different kinds of chemical modifications without leading to loss of activity. Compounds 4 and 6 can serve as potential lead compounds for further development of new anticancer drugs.     

One‐Pot Synthesis of New (1,3‐Thiazolo[5,4‐b]pyridin‐2‐yl)benzenediols and Their Antiproliferative Activities against Human Cancer Cell Lines

A one‐pot synthesis of new 4‐(1,3‐thiazolo[5,4‐b]pyridin‐2‐yl)benzene‐1,3‐diols has been described. The compounds were prepared by the reaction of sulfinylbis[(2,4‐dihydroxyphenyl)methanethione] derivatives, with various substituents in the aryl rings, with 2‐chloropyridin‐3‐amines. Their structures were deduced from IR and, ¹H‐ and ¹³C‐NMR spectroscopic, mass spectrometric, and elemental analyses. The antiproliferative properties of some of the products against human cancer cell lines were comparable to those of cisplatin. Structure? activity analysis showed that the presence of hydrophobic substituents in both heterocyclic fused and phenyl rings of the compounds improves their biological effects. Further, an additional OH group in the resorcinol moiety reduced the antiproliferative activity.     

Optimization of (Phenylmethylidene)‐hydantoins as Prostate Cancer Migration Inhibitors: SAR‐Directed Design,Synthesis, and Pharmacophore Modeling

Prostate cancer is one of the most common cancer forms among males of Western countries. Natural products proved to be an unparalleled source of molecular diversity. The 4‐(hydroxyphenylmethylidene)hydantoin (PMH; 1 ), (5Z)‐5‐(4‐hydroxybenzylidene)imidazolidine‐2,4‐dione, was isolated from the Red Sea sponge Hemimycale arabica, and recently showed junctional complexes stabilization, anti‐invasive, and antimetastatic activities in vitro and in vivo. The related synthetic analogue, (5Z)‐5‐[4‐(ethylsulfanyl)benzylidene]imidazolidine‐2,4‐dione ( 2 ), showed several‐fold‐improved in vivo antimetastatic properties against the highly invasive prostate cancer. To further optimize the activity of PMHs, various ligand‐based strategies were used including the extension of the structure, structural simplification, linker extension, and computer‐assisted CoMFA (Comparative Molecular Field Analysis) results. These strategies yielded thirty 2nd‐generation PMHs, designed based on the 1st‐generation PMHs, such as 1 and 2 . Wound‐healing assay was selected to evaluate the in vitro anti‐migratory potential of these new PMHs against the PC‐3 cell line. Several active PMHs, including 10, 13, 24, 29 , with nearly twelvefold enhancement of activity vs. 2 , were identified. Active compounds were then used to build a pharmacophore model using the SYBYL's DIStance COmparison technique (DISCOtech). Active PMHs were also screened for fragment‐based drug likeness using the OSIRIS program, and an overall drug score was also calculated. Interestingly, the overall drug scores of 24 and 29 along with their anti‐migratory activity were significantly greater than those of 1 and 2 . In conclusion, PMHs can be the appropriate scaffolds for the urgently needed drug candidates for the control of androgen independent prostate cancer.     

Synthesis and Structure?Activity Relationships of Antifungal Crassinervic Acid Analogs

A series of analogs of the natural antifungal compound crassinervic acid, a constituent of Piper crassinervium, were synthesized to gain insight into the most relevant structural features affecting the activity of the parent molecule. Most compounds were prepared by aldol reaction of methyl 3‐acetyl‐4‐hydroxybenzoate with a series of ketones, followed by reduction, hydrolysis, and oxidation. The antifungal activities of crassinervic acid and its analogs was assessed against Cladosporium cladosporioides by using the method of bioautography. The bioassay results allowed us to depict structure? activity relationships for this class of compounds.     

Synthesis and Antifungal Activities of Trichodermin Derivatives as Fungicides on Rice

Twenty new trichodermin derivatives, 2a – 5 , containing alkoxy, acyloxy, and Br groups in 4‐, 8‐, 9‐, 10‐ and 16‐positions were synthesized and characterized. The antifungal activities of the new compounds against rice false smut (Ustilaginoidea virens), rice sheath blight (Rhizoctonia solani), and rice blast (Magnaporthe grisea) were evaluated. The results of bioassays indicated that the antifungal activities were particularly susceptible to changes at 4‐, 8‐, and 16‐positions, but low to changes at 9‐ and 10‐positions. Most of these target compounds exhibited good antifungal activities at the concentration of 50 mg l^?1. Compound 4 (9‐formyltrichodermin; EC₅₀ 0.80 mg l^?1) with an CHO group at 9‐position displayed nearly the same level of antifungal activity against Ustilaginoidea virens as the commercial fungicide prochloraz (EC₅₀ 0.82 mg l^?1), while compound 3f ((8R)‐8‐{[(E)‐3‐phenylprop‐2‐enoyl]oxy}trichodermin; EC₅₀ 3.58 and 0.74 mg l^?1) with a cinnamyloxy group at C(8) exhibited much higher antifungal activities against Rhizoctonia solani and Magnaporthe grisea than the commercial fungicides prochloraz (EC₅₀ 0.96 mg l^?1) and propiconazole (EC₅₀ 5.92 mg l^?1), respectively. These data reveal that compounds 3f and 4 possess high antifungal activities and may serve as lead compounds for the development of fungicides in the future.     

Studies on Chemical‐Structure Modification and Structure?Activity Relationship of Gambogic Acid Derivatives at Carbon(34)

Gambogic acid (GA), a natural product, was identified as a promising antitumor agent. To further explore the structure? activity relationship of GA and discover novel GA derivatives as antitumor agents, 19 novel GA derivatives modified at C(34) were synthesized and evaluated against A549, BGC‐823, U251, HepG2, and MB‐231 cancer cell lines by cellular assays. Among them, 15 compounds were found to be more potent than GA against some cancer cell lines. Notably, compound 3 possessed potent inhibitory activities against five cell lines with IC₅₀ values ranging between 0.24 and 1.09 μM . Compounds 9 and 18 were seven to eightfold more active than GA against A549 cell line. Chemical modification at C(34) of GA by introducing of hydrophilic aliphatic amines resulted in increased activity and improved drug‐like properties. These findings will enhance our understanding of the SAR of GA and can lead to the discovery of novel GA derivatives as potential antitumor agents.     

Defensive Sesquiterpenes from Senecio candidans and S. magellanicus,and Their Structure?Activity Relationships

Eleven eremophilanolides, 1 – 3 and 6 – 13 , and two eremophilanes, 24 and 25 , were isolated from Senecio candidans and S. magellanicus from the Magallanes Region (Chile). Compounds 2, 3, 9 , and 10 have not been previously reported as natural products. Their structures were established by NMR spectroscopic analysis and chemical transformations. The X‐ray analysis of compounds 11, 13 , and 17 were also performed. Different semisynthetic analogs from eremophilanolide 11 were generated to carry out a structure? activity relationship study. Their possible plant defensive role was tested against herbivorous insects (Spodoptera littoralis, Rhopalosiphum padi, and Myzus persicae) and plants (Lactuca sativa). Additionally, their effects on insect (Sf9) and mammalian (CHO) cell lines were tested.     

Synthesis of novel derivatives of esculentoside A and its aglycone phytolaccagenin, and evaluation of their haemolytic activity and inhibition of lipopolysaccharide-induced nitric oxide production

A series of 46 compounds derived from esculentoside A and its aglycone were synthesized and characterized. The effect of these compounds on lipopolysaccharide (LPS)-induced NO production, haemolytic activity, and cell viability was evaluated. Structure-activity relationship was established by comparing the derivatives of esculentoside A with its aglycone derivatives. Both the aglycone and its derivatives showed higher inhibitory effects on LPS-induced NO production, and lower haemolytic activities than esculentoside A and its derivatives.     

Synthesis and Biological Assays of 9‐(Acylamino)homocamptothecins as DNA Topoisomerase I Inhibitors

In an effort to improve the stability of homocamptothecin and reduce the toxicity, novel homocamptothecin analogs with acylamino groups at C(9) were designed and synthesized. The cytotoxic activities of all the synthetic compounds against three cancer cell lines were evaluated by the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl‐2H‐tetrazolium bromide (MTT) assay, and irinotecan was used as reference compound. Compound 7c with a piperidinylacetamido group and 10a with phenylacetamido group at C(9) showed potent activities both in vitro and in vivo. In addition, they also revealed remarkable topoisomerase I inhibitions which were exhibited with well‐established bonds with amino acid residues Arg364 and Asp533 in the active pocket. On the basis of the biological activities, 7c and 10a would be potential candidates for further studies.     

Synthesis and Evaluation of Gambogic Acid Derivatives as Antitumor Agents. Part III

Gambogic acid (GA) has been reported as a potent apoptosis inducer. Previously, we have reported chemical modification at C(34) and C(39) of GA, leading to some agents with improved activity. To investigate the further structure? activity relationship (SAR) and preliminary mechanism of GA activity, a series of derivatives with modified prenyl side chains of GA were synthesized and evaluated. Most of the derivatives showed potent inhibitory activities against the proliferation of HepG2 and A549 cell lines. Compound 4 was selected for further mechanistic studies due to its outstanding activity. It was established that 4 induces the apoptosis of HepG2 cells by using Annexin‐V/PI double staining and Western blot assay, thus, compound 4 can serve as a promising lead compound for the development of novel apoptosis in anticancer treatment.     

Triterpenes from the fungus Poria cocos and their inhibitory activity on nitric oxide production in mouse macrophages via blockade of activating protein-1 pathway

Two new triterpenes, 29-hydroxydehydrotumulosic acid (1) and 29-hydroxydehydropachymic acid (2), together with six known compounds, dehydropachymic acid (3), dehydrotumulosic acid (4), 29-hydroxypolyporenic acid C (5), polyporenic acid C (6), tumulosic acid (7), and pachymic acid (8), were isolated from the dried sclerotia of Poria cocos. In the in vitro bioassays, these isolated compounds reduced, in a dose-dependent manner, nitric oxide (NO) production from lipopolysaccharide (LPS)-induced RAW 264.7 cells, with compounds 5 and 6, the IC(50) values of which were 16.8±2.7 and 18.2±3.3 μM, respectively, exhibiting the greatest inhibition activity. Further Western blot analysis conducted on cells pre-treated with compounds 5 and 6, and luciferase assays on activator protein 1-dependent gene expression revealed that the inhibited NO release was attributed to the reduced expression of iNOs (=inducible NO synthase) enzymes, which might be regulated via the blockade of activator protein-1 signaling pathway.     

Cyclopaldic Acid,Seiridin, and Sphaeropsidin A as Fungal Phytotoxins,and Larvicidal and Biting Deterrents against Aedes aegypti (Diptera: Culicidae): Structure?Activity Relationships

Aedes aegypti L. is the major vector of the arboviruses responsible for dengue fever, one of the most devastating human diseases. From a preliminary screening of fungal phytotoxins, cyclopaldic acid ( 1 ), seiridin ( 2 ), sphaeropsidin A ( 4 ), and papyracillic acid ( 5 ) were evaluated for their biting deterrent and larvicidal activities against Ae. aegypti L. Because compounds 1, 2, 4 , and 5 exhibited mosquito biting deterrent activities and 1 and 4 demonstrated larvicidal activities, further structure? activity relationship studies were initiated on these toxins. In biting‐deterrence bioassays, 1, 2, 4 , and 5 , 3,8‐didansylhydrazone of cyclopaldic acid, 1F , 5‐azidopentanoate of cyclopaldic acid A, 1G , the reduced derivative of cyclopaldic acid, 1 H , isoseiridin ( 3 ), 2′‐O‐acetylseiridin ( 2A ), 2′‐oxoseiridin ( 2C ), 6‐O‐acetylsphaeropsidin A ( 4A ), 8,14‐methylensphaeropsidin A methyl ester ( 4B ), and sphaeropsidin B ( 4C ) showed activities higher than the solvent control. Sphaeropsidin B ( 4C ) was the most active compound followed by 2A , while the other compounds were less active. Biting‐deterrence activity of compound 4C was statistically similar to DEET. In the larvicidal screening bioassays, only compounds 1 and 4 demonstrated larvicidal activities. Based on LD₅₀ values, compound 4 (LD₅₀ 36.8 ppm) was significantly more active than compound 1 (LD₅₀ 58.2 ppm). However, the activity of these compounds was significantly lower than permethrin.     

Hierarchical Hollow‐Microsphere Metal–Selenide@Carbon Composites with Rational Surface Engineering for Advanced Sodium Storage

As a result of its high‐energy density, metal–selenides have demanded attention as a potential energy‐storage material. But they suffer from volume expansion, dissolved poly‐selenides and sluggish kinetics. Herein, utilizing' thermal selenization via the Kirkendall effect, microspheres of NiSe₂ confined by carbon are successfully obtained from the self‐assembly of Ni‐precursor/PPy. The derived hierarchical hollow architecture increases the active defects for sodium storage, while the existing double N‐doped carbon layers significantly alleviate the volume swelling. As a result, it shows ultrafast rate capability, delivering a stable capacity of 374 mAh g^?1, even after 3000 loops at 10.0 A g^?1. These remarkable results may be ascribed to the Ni? O? C bonds on the interface of NiSe₂ and the carbon film, which leads to the faster transfer of ions, the effective trapping of poly‐selenide, and the highly reversible conversion reaction. The kinetic analysis of cyclic voltammetry (CV) demonstrates that the electrochemical process is mainly dominated by pseudocapacitive behaviors. Supported by the results of electrochemical impedance spectroscopy (EIS), it is confirmed that the solid–electrolyte interface films are reversibly formed/decomposed during cycling. Given this, this elaborate work might open up a potential avenue for the rational design of metal‐sulfur/selenide anodes for advanced battery systems.     

Synergetic DNA‐Cleaving Activities of the Metal Complexes of a Polyether‐Tethered Pyrrole‐polyamide Dimer

A simple polyether‐tethered pyrrole‐polyamide dimer 1 was synthesized in 50% yield from the reaction of 2,2,2‐trichloro‐1‐(1‐methyl‐4‐nitro‐1H‐pyrrol‐2‐yl)ethanone with 2,2′‐[1,2‐ethanediylbis(oxy)]bisethanamine, and fully characterized on the basis of ¹H‐ and ¹³C‐NMR, MS, HR‐MS, and IR data. Agarose gel‐electrophoresis study of the cleavage of plasmid pBR322 DNA by the complexes of compound 1 with seven metal ions indicated that most of the metal complexes were capable of efficiently cleaving DNA at pH 7.0 and 37°. Among them, the Cu^II complex exhibited the highest activity, with the maximal catalytic rate constant k_max and Michaelis constant K_M being 5.61 h^?1 and 7.30 mM , respectively. Spectroscopic, ESI‐MS, ethidium‐bromide (EB) displacement, and viscosity experiments indicated that compound 1 could form a 1 : 1 complex with Cu^II ion, and that this complex showed moderate binding affinity toward calf‐thymus DNA.     

Brain Pharmacokinetics of Non‐Imidazole Biphenyl H3 Receptor Antagonists: a Liquid Chromatography/Electrospray‐Mass Spectrometry and ex vivo Binding Study in Rats

In the present article, we report on the kinetics of brain penetration in rats of the H3R antagonist 1,1′‐[1,1′‐biphenyl‐4,4′‐diylbis(methylene)]bis‐[piperidine] ( 1 ), which had shown a favorable in vitro pharmacological profile and in vivo potency in preventing scopolamine‐induced amnesia. Two different approaches were employed: high‐performance liquid chromatography/electrospray‐mass spectrometry (HPLC/ESI‐MS) and ex vivo binding against the labeled agonist [³H]‐(R)‐α‐methylhistamine ([³H]RAMHA). Starting from the structure of 1 , the rigid piperidine ring was replaced by a flexible dipropylamino group (see 2 ) or by a morpholino ring (see 3 ), endowed with lower basicity. The effect of replacement on rat plasma and brain disposition in the 24 h after administration was analyzed. High (μM ) and persistent concentrations of 1 were found in rat plasma, while plasma levels were significantly lower (range: 0–200 nM ) for the other two derivatives. This could be explained, among other factors, by the higher stability, observed for 1 , to liver metabolic cleavage. The applied chemical modulation had an important effect on in vivo brain disposition, as, despite the comparable physico‐chemical properties, 2 did not show the tendency to accumulate within the brain, as stated by its brain vs. plasma concentration ratios, if compared to 1 . These structure? property relationships should be taken into account in the pharmacokinetic optimization of new series of H3 receptor antagonists.     

Structure?Activity Relationship of Polypyridyl Ruthenium(II) Complexes as DNA Intercalators,DNA Photocleavage Reagents,and DNA Topoisomerase and RNA Polymerase Inhibitors

To investigate the relationship between the molecular structure and biological activity of polypyridyl Ru^II complexes, such as DNA binding, photocleavage ability, and DNA topoisomerase and RNA polymerase inhibition, six new [Ru(bpy)₂(dppz)]²⁺ (bpy=2,2′‐bipyridine; dppz=dipyrido[3,2‐a:2,′,3′‐c]phenazine) analogs have been synthesized and characterized by means of ¹H‐NMR spectroscopy, mass spectrometry, and elemental analysis. Interestingly, the biological properties of these complexes have been identified to be quite different via a series of experimental methods, such as spectral titration, DNA thermal denaturation, viscosity, and gel electrophoresis. To explain the experimental regularity and reveal the underlying mechanism of biological activity, the properties of energy levels and population of frontier molecular orbitals and excited‐state transitions of these complexes have been studied by density‐functional theory (DFT) and time‐depended DFT (TDDFT) calculations. The results suggest that DNA intercalative ligands with better planarity, greater hydrophobicity, and less steric hindrance are beneficial to the DNA intercalation and enzymatic inhibition of their complexes.