Inhibition of amyloid fibril formation and disassembly of pre-formed fibrils by natural polyphenol rottlerin

Natural polyphenols, curcumin, rottlerin and EGCG were selected for initial computational modeling of protein-ligand interaction patterns. The docking calculations demonstrated that these polyphenols can easily adjust their conformational shape to fit well into the binding sites of amyloidogenic proteins. The experimental part of the study focused on the effect of rottlerin on fibrillation of three distinct amyloidogenic proteins, namely insulin, lysozyme and Aβ_1–40 peptide. Different experimental protocols such as fluorescence spectroscopy, circular dichroism and atomic force microscopy, demonstrated that amyloid fibril formation of any of the three proteins is inhibited by low micromolar rottlerin concentrations. Most likely, the inhibition of amyloid formation proceeded via interaction of rottlerin with amyloidogenic regions of the studied proteins. Moreover, rottlerin was also effective in pre-formed fibrils disassembly, suggesting that interactions of rottlerin with fibrils were capable to interrupt the fibril-stabilizing bonds of β-sheets. The apparent IC₅₀ and DC₅₀ values were calculated in the range of 1.3–36.4 μM and 15.6–25.8 μM, respectively. The strongest inhibiting/disassembling effect of rottlerin was observed on Aβ_1–40 peptide. The cytotoxicity assay performed on the Neuro 2a cells indicated time-dependent cell morphology changes but rottlerin affected the cell viability only at concentration above 50 μM. The results of this study suggest that chemical modifications on rottlerin could be tested in the future as a promising strategy for the modulation of amyloidogenic proteins aggregation.     

Phytochemical and Bioactivity Studies on Constituents of the Leaves of Vitex Quinata

A phytochemical investigation of the leaves of Vitex quinata (Lour.) F.N. Williams (Verbenaceae), guided by a cytotoxicity assay against the MCF-7 human breast cancer cell line, led to the isolation of a new δ-truxinate derivative (1) and a new phytonoic acid derivative (2), together with 12 known compounds. The structures of the new compounds were determined by spectroscopic methods as dimethyl 3,4,3′,4′-tetrahydroxy-δ-truxinate (1) and methyl 10R-methoxy-12-oxo-9(13),16E-phytodienoate (2), respectively. In a cytotoxicity assay, (S)-5-hydroxy-7,4′-dimethoxyflavanone (3) was found to be the sole active principle, with ED₅₀ values of 1.1–6.7 μM, respectively, when tested against a panel of three human cancer cells. Methyl 3,4,5-O-tricaffeoyl quinate (4) showed activity in an enzyme-based ELISA NF-κB p65 assay, with an ED₅₀ value of 10.3 μM.     

Cytotoxic ent‐Kaurane Diterpenoids from Isodon nervosus

Four new ent‐kaurane diterpenoids, rabdonervosins G–J ( 1 – 4 , resp.), were isolated from the leaves and stems of Isodon nervosus. Their structures were elucidated by extensive spectroscopic analyses, including 1D‐, 2D‐NMR and HR mass spectra. Compound 2 showed potent cytotoxicity against the HepG2 and PC‐9/ZD cell lines with IC₅₀ values of 2.36 and 6.07 μM , respectively, and compound 3 exhibited cytotoxicity against the HepG2 and CNE2 cell lines with IC₅₀ values of 8.64 and 9.77 μM , respectively.     

Cytotoxic Diterpenoids from Euphorbia fischeriana

Five new diterpenoids, named euphorfischerins A–E, were isolated from the roots of Euphorbia fischeriana. Their chemical structures and absolute configurations were determined by interpretation of NMR, HR-ESI-MS, ECD and X-ray diffraction data. Euphorfischerin A showed cytotoxicity against the human cancer cell lines HeLa, H460 and Namalwa with IC₅₀ values of 4.6, 11.5 and 16.4 μM, respectively, while euphorfischerin B gave comparable IC₅₀ values of 9.5, 17.4 and 13.3 μM against the three cancer cell lines, respectively.     

Synthesis and Anticancer Activity of 3-(3-Oxoprop-1-enyl)-Substituted Analogues of Carbocyclic Pyrimidine Nucleosides and 2′,3′-Dideoxy Pyrimidine Nucleosides

Abstract

Various 2′, 3′ -dideoxy and carbocyclic pyrimidine nucleosides, and their corresponding 3-(3-oxoprop-1-enyl) derivatives, have been synthesized and evaluated against murine L1210 and P388 leukemias and Sarcoma 180 and human CCRF-CEM lymphoblastic leukemia. Among the compounds tested, 3-(3-oxoprop-1-enyl)-3′ -fluoro-3′ -deoxythymidine (17), 3-(3-oxoprop-1-enyl)-3′ -azido-3′ -deoxythymidine (15) and 3-(3-oxoprop-1-eny!)-(+)-1-[(lα, 3β, 4α)-3-hydroxy-4-(hydroxymethyl)cyclopentyl]-5-methyl-2,4 (lH,3H)pyrimidinedione (6) were found to be the most active with ED₅₀, values of 0.5,0.2,0.1, and 0.3 μM; 1.2, 0.5,1.0 and 1.0 μM; and 0.8,0.7,1.5, and 3.0μM, respectively. Our preliminary findings indicate that the 3-(3-oxoprop-1-enyl) derivative of carbocyclic thymidine is approximately 7 times more active than the 3-(3-oxoprop-1-enyl) derivative of carbocyclic thymine riboside against L1210 leukemia cells in vitro, with ED₅₀ values of 0.8 μM and 5.5 μM, respectively. These findings suggest that the cytotoxicity of these compounds not only is dependent upon the 3-(3-oxoprop-1-enyl)-substituted group, but also may vary with the sugar moiety.     

Study of Antimalarial Activity of Chemical Constituents from Diospyros quaesita

Bioassay‐directed fractionation led to the isolation of seven compounds from a sample of the dried leaves, twigs, and branches of Diospyros quaesita Thw . (Ebenaceae). One of the isolates, betulinic acid 3‐caffeate ( 1 ), showed in vitro antimalarial activity against Plasmodium falciparum clones D₆ (chloroquine‐sensitive) and W₂ (chloroquine‐resistant) with IC₅₀ values of 1.40 and 0.98 μM , respectively. Evaluation of compound 1 in the human oral epidermoid (KB) cancer cell line revealed cytotoxicity at ED₅₀ of 4.0 μM . In an attempt to reduce the cytotoxicity of 1 , the acetylated derivative 1a and betulinic acid ( 1b ) were prepared. Of the seven isolates, diospyrosin ( 2 ) was determined to be a new neolignan. In addition to 1 , other known compounds isolated in this study were pinoresinol, lariciresinol, N‐benzoyl‐L ‐phenylalaninol, scopoletin, and poriferast‐5‐en‐3β,7α‐diol. The structure of 2 was elucidated based on spectroscopic data analysis including 1D‐ and 2D‐NMR, and HR‐ESI‐MS.     

Synthesis and antitumor activity of 1-β-D-arabinofuranosylcytosine-5′-diphosphate-prednisolone and -cortisol

Superior antitumor activity and reduced toxicity of 1-β-arabinofuranosylcytosine (ara-C) conjugates of corticosteroids through a phosphodiester linkage have prompted us to synthesize the new ara-C conjugates of corticosteroids through a pyrophosphate diester linkage. Condensation of ara-CMP morpholidate with the steroid-21-monophosphates in pyridine at room temperature for 6 days and the subsequent separation on a DE-52 (formate) column using a linear gradient of 0?0.5 M triethylammonium formate (pH 7.0) gave ara-CDP-prednisolone (I) and ara-CDP-cortisol (II) in 37–55% yield. The conjugates were hydrolyzed to ara-CMP and the corresponding steroid-21-monophosphate by phosphodiesterase I. Conjugates I and II inhibited the $\text{in}\text{,}\text{vitro}$ growth of L1210 lymphoid leukemia by 50% (ED₅₀) at 0.03 and 0.08 μM, respectively, while ara-C and ara-CMP showed the respective ED₅₀ of 0.1 μM and 0.05 μM. Conjugates I and II exhibited ILS values of 116 and 86%, respectively, at 40 mg (53.7 μmole)/kg/day × 5 against L1210 leukemic mice, while that of ara-C at the nearly same dose (49 μmole/kg/day × 5) was 65%.     

Cytotoxic and α-Glucosidase Inhibitory Xanthones from Garcinia mckeaniana Leaves and Molecular Docking Study

A new racemic xanthone, garmckeanin A ( 1 ), and eight known analogs 2 – 9 were isolated from the ethyl acetate (AcOEt) extract of the Vietnamese Garcinia mckeaniana leaves. Their structures were determined by MS and NMR spectral analyses and compared with the literature. The AcOEt extract showed good cytotoxicity against cancer cell lines KB, Lu, Hep-G2 and MCF7, with IC₅₀ values of 5.40–8.76 μg/mL, and it also possessed α-glucosidase inhibitory activity, with an IC₅₀ value of 9.17 μg/mL. Garmckeanin A ( 1 ) exhibited inhibition of all cancer cell lines, with an IC₅₀ value of 7.3–0.9 μM. Allanxanthone C ( 5 ) successfully controlled KB growth, with an IC₅₀ value of 0.54 μM, higher than that of the positive control, ellipticine (IC₅₀ 1.22 μM). Norathyriol ( 8 ) was a promising α-glucosidase inhibitor, with an IC₅₀ value of 0.07 μM, much higher than that of the positive control, acarbose (IC₅₀ 161.0 μM). The interactions of the potential α-glucosidase inhibitors with the C- and N-terminal domains of human intestinal α-glucosidase were also investigated by molecular docking study. The results indicated that bannaxanthone D ( 2 ), garcinone E ( 4 ), bannaxanthone E ( 6 ), and norathyriol ( 8 ) exhibit higher binding affinity to the C-terminal than to the N-terminal domain through essential residues in the active sites. In particular, compound 8 could be assumed to be the most potent mixed inhibitor.     

Chemical Constituents of Primulina eburnea (Gesneriaceae) and Their Cytotoxic Activities

Two new ursane-type triterpenes, eburnealactones A and B ( 1 and 2 ), one new flavonoid, eburneatin A ( 6 ), and one new phenylethanoid glycoside, chiritoside D ( 7 ), along with 9 known compounds ( 3–5 , 8–13 ) were isolated from the whole plant of Primulina eburnea. Their structures were elucidated by comprehensive spectroscopic data analysis (IR, UV, NMR, and HR-ESI-MS). All the compounds were evaluated for their cytotoxic activities. Compound 1 showed significant cytotoxic activities against MKN-45 cell lines and 5637 cell lines with the IC₅₀ values of 9.57 μM and 8.30 μM, respectively. Compound 1 exhibited moderate cytotoxic activities against A549 and PATU8988T cell lines with the IC₅₀ values of 30.70 μM and 38.22 μM, respectively. Compound 6 exhibited moderate cytotoxic activities against MKN-45, HCT116, PATU8988T, 5637 and A-673 cell lines with the IC₅₀ values of 19.69 μM, 16.44 μM, 18.07 μM, 11.51 μM and 18.15 μM, respectively. Compound 5 showed moderate cytotoxic activities against A549 cell lines with the IC₅₀ values of 24.06 μM.     

Synthesis and Antiviral Activities of 5-Substituted 1-(2-Deoxy-2-C-methylene-4-thio-β-D-erythro-pentofuranosyl)uracilst†

Abstract

Various 5-substituted 1-(2-deoxy-2-C-methylene-4-thio-β-D-erythropentofuranosyl)uracils (4′-thioDMDUs) were synthesized from D-glucose via sila-Pummerer-type glycosylation. All of the β-anomers of 5-substituted 4′-thioDMDU, except the 5-hydroxyethyl derivative, showed potent anti-HSV-1 activity (ED₅₀ = 0.016–0.096 μg/mL). 5-Ethyl- and 5-iodo-4′-thioDMDUs were also active against HSV-2 (ED₅₀ = 0.17 and 0.86 μg/mL, respectively). 5-Bromovinyl-4′-thioDMDU was particularly active against VZV (ED₅₀ = 0.013 μg/mL).

     

New Rosane Diterpenoids and Their Analogs from Euphorbia ebracteolata Hayata

Phytochemical investigation of the roots of Euphorbia ebracteolata Hayata resulted in the isolation of three new rosane diterpenoids, euphebracteolatins C–E ( 1 – 3 ), along with fourteen known analogs ( 4 – 17 ). Their structures were determined on the basis of extensive spectroscopic analysis including HR-ESI-MS, 1D and 2D NMR. Euphebracteolatin C ( 1 ) contains a C-1/C-10 double bond and a keto group at C-7, and euphebracteolatins D and E ( 2 – 3 ) possess an aromatic ring-A in their skeleton. The plausible biogenetic pathways of all the isolates were also proposed. Furthermore, compounds 1 and 9 showed selective cytotoxicity against HepG2 cells with IC₅₀ values of 14.29 and 12.33 μM, respectively, and 2 – 3 displayed moderate cytotoxicity against three human cancer lines, with IC₅₀ values ranging from 23.69 to 39.25 μM.     

ATP analogues and other phosphate compounds as gorging stimulants for Rhodnius prolixus

Five analogues of ATP and six other non-nucleotide compounds with phosphate groups were tested as gorging stimulants for second-instar larvae of Rhodnius prolixus to determine the importance of the phosphate chain. Only molecules with terminal phosphate groups were potent. Insertion of an imido group (5′-Adenylylimidodiphosphate, AMP-PNP) or a methylene group (β, γ-Methylene adenosine 5′-triphosphate, AMP-PCP) between the β and γ phosphates of ATP reduced the potency compared to ATP by ratios of 1.8 and 25.5, respectively. Substituting ribose (Adenosine 5′-diphosphoribose, AMP-PR) for the γ phosphate group or an amidate or a sulphate group (Adenosine 5′-phosphoramidate, AMP-N; Adenosine 5′-phosphosulphate, AMP-S) for the β and γ phosphate groups of ATP resulted in a complete loss of stimulatory activity.Some non-nucleotide phosphate compounds were potent phagostimulants. Pyrophosphate with an ED₅₀ of 64 μM had a potency ratio compared with ATP of 1:17. Methylene diphosphonic acid (ED₅₀ 680 μM) and even single phosphate ions (ED₅₀ 2.5 mM) had substantial potency. Two isomers of phosphoglyceric acid differ greatly in their ability to stimulate gorging; 2-PGA was active (ED₅₀ 160 μM) whereas 3-PGA had almost no activity.A summary of known phagostimulants to R. prolixus supports the hypothesis that ATP-like gorging stimulants act by forming a temporary binding to 3 sites on a receptor protein in the membrane of the chemosensory cell. The amino group on C₆ of adenine, the OH group on C₂ of ribose and the terminal phosphate group(s) determine potency, presumably by determining binding affinity. However, only the phosphate group appears essential to the chemosensory process.     

Synergistic effect of the interaction between curcumin and diclofenac on the formalin test in rats

The association of non-steroidal anti-inflammatory drugs with certain plant extracts can increase antinociceptive activity, permitting the use of lower doses and thus limiting side effects. Therefore, the aim objective of the current study was to examine the effects of curcumin on the nociception and pharmacokinetics of diclofenac in rats. Antinociception was assessed using the formalin test. Diluted formalin was injected subcutaneously into the dorsal surface of the right hind paw. Nociceptive behavior was quantified as the number of flinches of the injected paw during 60 min after injection, and a reduction in formalin-induced flinching was interpreted as an antinociceptive response. Rats were treated with oral diclofenac (1–31 mg/kg), curcumin (3.1–100 mg/kg) or the diclofenac–curcumin combination (2.4–38.4 mg/kg). To determine the possibility of a pharmacokinetic interaction, the oral bioavailability of diclofenac (10 mg/kg) was studied in presence and the absence of curcumin (31 mg/kg). Diclofenac, curcumin, or diclofenac–curcumin combination produced an antinociceptive effect on the formalin test. ED₃₀ values were estimated for the individual drugs, and an isobologram was constructed. The derived theoretical ED₃₀ for the antinociceptive effect (19.2 mg/kg) was significantly different from the observed experimental ED₃₀ value (9.8 mg/kg); hence, the interaction between diclofenac and curcumin that mediates the antinociceptive effect was synergistic. Notwithstanding, the interaction does not appear to involve pharmacokinetic mechanisms, as oral curcumin failed to produce any significant alteration in oral diclofenac bioavailability. Data suggest that the diclofenac–curcumin combination can interact at the systemic level and may have therapeutic advantages for the clinical treatment of inflammatory pain.     

Synthesis,characterization, and anticancer evaluation of novel 4-hydrazinothiazole analogs

Single-step synthesis of novel 4-hydrazinothiazole derivatives 6a–e was achieved under mild conditions using the sequential four-components method involving isothiocyanate, aminoguanidine, carbonyl adduct, and α-haloketone derivatives. Deprotection of these hydrazinothiazoles was influenced by acylation, providing a novel group of diacylated molecular structures with a broader scope for the design of thiazolyl-containing drugs 7a and 7b . FTIR, ¹H/¹³C NMR, LC–MS spectroscopy, and CHN elemental analyses were used to study the compound chemical structures. Using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay on human periodontal ligament fibroblast (HPDLF) cells, the 4-hydrazinothiazole derivatives were screened for cytotoxicity in an in vitro cytotoxicity investigation. The 4-hydrazinothiazole compound 6b bearing an isopropylidene-hydrazino group demonstrated strongly potent cytotoxicity against CAKI1 (IC₅₀ = 1.65 ± 0.24 μM) and A498 (IC₅₀ of 0.85 ± 0.24 μM). Furthermore, the chloroacetyl-containing thiazole compound 7a displayed efficient inhibition of growth against the test cell lines CAKI1 and A498 at low micromolar concentrations, IC₅₀ 0.78 and 0.74 μM, respectively.     

Cytotoxic macrocyclic diterpenoids from Jatropha multifida

Nine new macrocyclic diterpenoids (1–9), jatromultones A-I, along with eight known analogues (10–17) were isolated from the trunks of Jatropha multifida. The structures of the new compounds, including their absolute configurations, were elucidated by combination of spectroscopic analysis, single crystal X-ray diffraction, Rh₂(OCOCF₃)₄-induced CD method, and chemical correlations. All compounds were screened for the cytotoxicity against five cancer cell lines, including one drug-resistant cell line, and seven compounds exhibited significant activity with IC₅₀ values less than 10 μM. Compound 4 with IC₅₀ values ranging from 2.69 to 6.44 μM toward all cell lines was selected for further mechanistic study, which showed that 4 could arrest cell cycle at G2/M phase and induce apoptosis. The brief structure-activity relationships (SARs) of these macrocyclic diterpenoids were also discussed.     

Inhibition of nucleic acid synthesis in leukemia 1210 cells by antimetabolites of coenzyme Q10

Thirteen diversified antimetabolites of coenzyme Q₁₀ which have antitumor activity $\text{in vivo}$ were tested for inhibition of uptake of tritiated thymidine and uridine into DNA and RNA, respectively, of L1210 cells grown in tissue culture. Eight of these antimetabolites have inhibitory activities of the same order of magnitude as the used anticancer drugs, rubidazone and ellipticine. 5-ω-Phenylpropylmercapto-2,3-dimethoxy-1,4-benzoquinone was particularly potent to inhibit nucleic acid synthesis; ED₅₀ for DNA = 2.1 μM and ED₅₀ for RNA = 4.0 μM.     

ent-Herqueidiketal and epi-Peniciherqueinone Isolated from a Mushroom Derived Fungus Penicillium herquei YNJ-35

A new polyaromatic metabolite, ent-herqueidiketal ( 1 ), and a new phenalenone derivative, epi-peniciherqueinone ( 2 ), along with twelve known compounds 3 – 14 , were isolated from the fungus Penicillium herquei YNJ-35, a symbiotic fungus of Pulveroboletus brunneopunctatus collected from Nangunhe Nature Reserve, Yunnan Province, China. The structures of 1 – 14 and the absolute configurations of 1 and 2 were determined by their spectroscopic data or by their single-crystal X-ray diffraction analysis or optical rotation values. Compound 1 showed strong antibacterial activity against Staphylococcus aureus (ATCC 29213) with minimum inhibitory concentration (MIC) of 8 μg/mL. In the cytotoxicity assays, compound 1 showed weak inhibitory activity against breast cancer MCF-7 and mice microglial BV2 cells with half maximal inhibitory concentration (IC₅₀) of 17.58 and 29.56 μM; compound 14 showed stronger cytotoxicity against BV2 and MCF-7 cells with IC₅₀ values of 6.57 and 10.26 μM.     

Lanceoleins A–G,hydroxychalcones, from the flowers of Coreopsis lanceolata and their chemopreventive effects against human colon cancer cells

Seven new chalcones, lanceolein A–G (compounds 5 and 7–12), as well as five known chalcones (1–4 and 6), were isolated from the methanolic extract of Coreopsis lanceolata flowers. The chemical structures of 5 and 7–12 were determined on the basis of spectroscopic data interpretation. All compounds inhibited the production of nitrite oxide (NO) induced by LPS in RAW264.7 macrophage cells. Also, compounds 1–6 showed moderated cytotoxicity against human colon cancer cell lines, while compounds 7–12 hardly showed the cytotoxicity. Especially, compounds 2, 5, and 6 exhibited a little higher cytotoxicity on HCT15 cells, with IC₅₀ values of 43.7 ± 2.17 μM, 35.6 ± 0.24 μM, and 47.9 ± 1.18 μM, respectively. In the Tali assay, compounds 2 and 5 increased the numeral of apoptotic cells. These compounds also significantly promoted the expression of apoptotic proteins including PARP and caspase-3.     

Chemical Constituents of the Vietnamese Marine Sponge Gelliodes sp. and Their Cytotoxic Activities

A new decenoic acid derivative, gelliodesinic acid, and a naturally new alkaloid, together with three known furanoterpenoids and two known indole alkaloids, were isolated from the MeOH extract of the marine sponge Gelliodes sp. collected in Vietnam. The chemical structures of the isolated compounds were determined by analyses of 1D‐ and 2D‐NMR and MS data and by comparisons of the data with those reported in the literature. The cytotoxicity assay against HeLa, MCF‐7, and A549 cancer cell lines revealed that the three known furanoterpenes exhibited cytotoxic activities with IC₅₀ values ranging from 23.6 to 75.5 μM against the three cell lines, and that 1H‐indole‐3‐carboxylic acid showed cytotoxicity with an IC₅₀ value of 89.2 μM against A549 cancer cell lines.     

Hyposterolactone A,a 3α-Hydroxy Steroidal Lactone from the Deep-Sea-Derived Fungus Hypocrea sp. ZEN14

Chemical investigation of the deep-sea-derived fungus Hypocrea sp. ZEN14 afforded a new 3α-hydroxy steroidal lactone, hyposterolactone A ( 1 ) and 25 known secondary metabolites ( 2 – 26 ). The structure of the new compound was established by detailed spectroscopic analysis, electronic circular dichroism (ECD) calculation as well as a J-based configuration analysis. Compound 10 showed potent cytotoxicity against Huh7 and Jurkat cells with IC₅₀ values of 1.4 μM and 6.7 μM, respectively.