Structure-activity relationships of antileishmanial and antimalarial chalcones

A series of oxygenated chalcones which have been evaluated earlier for antimalarial activity (Plasmodium falciparum K1) were tested for antileishmanial activity against Leishmania donovani amastigotes. A comparison of structure-activity relationships reveal that different physicochemical and structural requirements exist for these two activities. Antileishmanial activity is associated with less lipophilic chalcones, in particular those with 4'-hydroxyl-substituted B rings and hetero/polyaromatic A rings. In contrast, chalcones with good antimalarial activity have alkoxylated B rings and electron-deficient A rings. Visualization of the steric and electrostatic fields generated from comparative molecular field analysis (CoMFA) indicate that the ring A of chalcones make a more significant contribution to antileishmanial activity while both rings A and B are important for antimalarial activity. Despite different requirements, two alkoxylated chalcones (8, 19) were identified which combined good antimalarial and antileishmanial activities.     

Antimalarial xanthones from Calophyllum caledonicum and Garcinia vieillardii

The antimalarial activity of 22 xanthones against chloroquino-resistant strains of Plasmodium falciparum was evaluated. Natural caloxanthone C (1), demethylcalabaxanthone (2), calothwaitesixanthone (3), calozeyloxanthone (4), dombakinaxanthone (5), macluraxanthone (6), and 6-deoxy-gamma-mangostin (7) were isolated from Calophyllum caledonicum. 1,6-dihydroxyxanthone (8), pancixanthone A (9), isocudraniaxanthone B (10), isocudraniaxanthone A (11), 2-deprenylrheediaxanthone B (12) and 1,4,5-trihydroxyxanthone (13) were isolated from Garcinia vieillardii. Moreover, synthetic compounds (14-22) are analogues or intermediates of xanthones purified from Calophyllum caledonicum (Oger J.M., Morel C., Helesbeux J.J., Litaudon M., Seraphin D., Dartiguelongue C., Larcher G., Richomme P., Duval O. 2003. First 2-Hydroxy-3-Methylbut-3-Enyl substituted xanthones isolated from Plants: structure elucidation, synthesis and antifungal activity. Natural Product Research 17(3), 195-199; Helesbeux J.J., Duval O., Dartiguelongue C., Seraphin D., Oger J.M., Richomme P., 2004. Synthesis of 2-hydroxy-3-methylbut-3-enyl substituted coumarins and xanthones as natural products. Application of the Schenck ene reaction of singlet oxygen with ortho-prenylphenol precursors. Tetrahedron 60(10), 2293-2300). The relationship between antimalarial activity and molecular structure of xanthones has also been explored. The most potent xanthones (2), (3) and (7) (IC50 = c.a. 1.0 microg/mL) are 1,3,7 trioxygenated and prenylated on the positions 2 and 8.     

Antibacterial and antimalarial properties of peptides that are cecropin-melittin hybrids

Solid phase synthesis was used to produce 5 hybrid peptides containing sequences from the antibacterial peptide, cecropin A, and from the bee venom toxin, melittin. Four of these chimeric peptides showed good antibacterial activity against representative Gram-negative and Gram-positive bacterial species. The best hybrid, cecropin A(1-13)-melittin(1-13) was 100-fold more active than cecropin A against Staphylococcus aureus. It was also a 10-fold better antimalarial agent than cecropin B or magainin 2. Sheep red cells were lysed by melittin at low concentrations, but not by the hybrid molecules, even at 50 times higher concentrations.     

Antiproliferative activity of novel thiopyran analogs on MCF-7 breast and HCT-15 colon cancer cells: synthesis, cytotoxicity, cell cycle analysis, and DNA-binding

A series of 6H-thiopyran-2,3-dicarboxylate derivatives 4a-d were synthesized and evaluated for their cytotoxic effect against HCT-15 colon and MCF-7 breast cancer cell lines using Sulforhodamine B (SRB) assay. The results showed that these compounds could exhibit a good cytotoxicity to both cell lines. In addition, these compounds were found to exhibit significant DNA-binding affinity. Ultraviolet-visible light (UV-Vis) spectroscopy was conducted to determine the ability of the ligand under analysis. The effect of ligand complexation on DNA structure led to overall affinity constants of K(4a)=3.5×10(4) M(-1), K(4b)=6.4×10(4) M(-1), K(4c)=3.2×10(4) M(-1), and K(4d)=2.4×10(4) M(-1). Our findings could provide new evidence showing the relationship between the chemical structure and biological activity and may be useful for the discovery of new anti-cancer drugs.     

Novel oxazine skeletons as potential antiplasmodial active ingredients: Synthesis, in vitro and in vivo biology of some oxazine entities produced via cyclization of novel chalcone intermediates

A novel series of 6-(2-chloroquinolin-3-yl)-4-substituted-phenyl-6H-1,3-oxazin-2-amines were synthesized and evaluated for in vitro antimalarial efficacy against chloroquine sensitive (MRC-02) as well as chloroquine resistant (RKL9) strains of Plasmodium falciparum. The activity tested was at nanomolar concentration. β-Hematin formation inhibition activity (BHIA(50)) of oxazines were determined and correlated with antimalarial activity. A reasonably good correlation (r?=?0.49 and 0.51, respectively) was observed between antimalarial activity (IC(50)) and BHIA(50). This suggests that antimalarial mode of action of these compounds seems to be similar to that of chloroquine and involves the inhibition of hemozoin formation. Some of the compounds were showing better antimalarial activity than chloroquine against resistant strain of P. falciparum and were also found to be active in the in vivo experiment.     

An automated, polymer-assisted strategy for the preparation of urea and thiourea derivatives of 15-membered azalides as potential antimalarial chemotherapeutics

A series of 15-membered azalide urea and thiourea derivatives has been synthesized and evaluated for their in vitro antimalarial activity against chloroquine-sensitive (D6), chloroquine/pyremethamine resistant (W2) and multidrug resistant (TM91C235) strains of Plasmodium falciparum. We have developed an effective automated synthetic strategy for the rapid synthesis of urea/thiourea libraries of a macrolide scaffold. Compounds have been synthesized using a solution phase strategy with overall yields of 50-80%. Most of the synthesized compounds had inhibitory effects. The top 10 compounds were 30-65 times more potent than azithromycin, an azalide with antimalarial activity, against all three strains.     

2-N-Methyl modifications and SAR studies of manzamine A

Quaternary carbolinium salts have been reported to show improved antimalarial activity and reduced cytotoxicity as compared to electronically neutral beta-carbolines. In this study, mono- and di-methylated quaternary carbolinium cations of manzamine A were synthesized and evaluated for their in vitro antimalarial and antimicrobial activity, cytotoxicity, and also their potential for glycogen synthase kinase (GSK-3beta) inhibition using molecular docking studies. Among the analogs, 2-N-methylmanzamine A (2) exhibited antimalarial activity (IC(50) 0.7-1.0microM) but was less potent than manzamine A. However the compound was significantly less cytotoxic to mammalian kidney fibroblasts and the selectivity index was in the same range as manzamine A.     

Effective discrimination of antimalarial potency of artemisinin compounds based on quantum chemical calculations of their reaction mechanism

The reaction mechanism of 12 antimalarial artemisinin compounds with two competitive pathways was studied by means of quantum chemical calculations using the IMOMO(B3LYP/6-31(d,p):HF/3-21G) method. The oxygen-centered radicals, carbon-centered radicals, and transition states (TS) in both pathways were geometrically optimized. The obtained kinetic and thermodynamic energy profiles show that homolytic C-C cleavage reaction (pathway 2) is energetically more preferable than an intramolecular 1,5-hydrogen shift process (pathway 1), which is consistent with the docking calculations. However, compounds that can easily proceed along the pathway 1 have high activity. Therefore, both pathways are important for antimalarial activity. Moreover, effective discrimination between high and low activity compounds using EA1, deltaE1, and deltaE(1A-2A) was accomplished.     

Novel oxazine skeletons as potential antiplasmodial active ingredients: Synthesis,in vitro and in vivo biology of some oxazine entities produced via cyclization of novel chalcone intermediates

A novel series of 6-(2-chloroquinolin-3-yl)-4-substituted-phenyl-6H-1,3-oxazin-2-amines were synthesized and evaluated for in vitro antimalarial efficacy against chloroquine sensitive (MRC-02) as well as chloroquine resistant (RKL9) strains of Plasmodium falciparum. The activity tested was at nanomolar concentration. β-Hematin formation inhibition activity (BHIA₅₀) of oxazines were determined and correlated with antimalarial activity. A reasonably good correlation (r?=?0.49 and 0.51, respectively) was observed between antimalarial activity (IC₅₀) and BHIA₅₀. This suggests that antimalarial mode of action of these compounds seems to be similar to that of chloroquine and involves the inhibition of hemozoin formation. Some of the compounds were showing better antimalarial activity than chloroquine against resistant strain of P. falciparum and were also found to be active in the in vivo experiment.     

S-Euglobals: biomimetic synthesis, antileishmanial, antimalarial, and antimicrobial activities

Several new euglobal analogues (named as S-euglobals) were synthesized from phloroglucinol via a biomimetic three-component reaction involving Knoevenagel condensation followed by [4+2]-Diels-Alder cycloaddition with monoterpene. Newly synthesized euglobal analogues involve monoterpenes that have not yet been encountered in natural euglobals. S-Euglobals along with previously synthesized robustadial A and B were evaluated for in vitro antileishmanial, antimalarial, antimicrobial, and cytotoxic activities. Out of 16, nine analogues were found to exhibit antileishmanial activity against Leishmania donovani promastigotes. Analogue 7 was the most potent with IC(50) of 2.4 microg/mL and IC(90) of 8 microg/mL, followed by analogues 8 and 11 (IC(50) 5.5 and 9.5 microg/mL). Antileishmanial activity of robustadial A (5) and B (6) was moderate with IC(50) of 20 and 16 microg/mL, respectively. Robustadial A and B and S-euglobal 8 exhibited weak antimalarial activity against Plasmodium falciparum (IC(50) of 2.7-4.76 microg/mL). Few of the euglobal analogues showed antibacterial activity against methicillin-resistant Staphylococcus aureus. Amongst these, analogue 11 was the most potent with IC(50) of 1.0 microg/mL and MIC of 5.0 microg/mL. Most of the compounds were not cytotoxic up to 25 microg/mL in a panel of cell lines consisting of both cancer (SK-MEL, KB, BT-549, and SK-OV-3) as well as non-cancer kidney (Vero and LLC-PK11) cells.     

Synthesis, antimalarial, antileishmanial, and antimicrobial activities of some 8-quinolinamine analogues

In the present communication, newly synthesized 8-quinolinamines (25-27) related to previously reported 2-tert-butylprimaquine (2) were evaluated for their in vitro antimalarial activity against chloroquine sensitive and resistant Plasmodium falciparum strains, in vivo antimalarial activity against P. berghei infected mice, in vitro antileishmanial activity against Leishmania donovani, in vitro antimicrobial activity against various fungi and bacteria, and cytotoxicity in a panel of mammalian cell lines. No promising cytotoxicities were observed for compounds reported herein. Analogue 25 was found to exhibit curative antimalarial activity at a dose of 25 mg/kg/dayx4 in a P. berghei infected mice model, and produced suppressive activity at a lower dose of 10 mg/kg/dayx4. In vitro antileishmanial activities (IC50 and IC90) comparable to standard drug pentamidine were exhibited by all synthesized 8-quinolinamines 25-27. At the same time, promising antibacterial and antifungal activities were also observed for synthesized compounds against a panel consisting of several bacteria and fungi.     

Assay of acetylcholinesterase activity by potentiometric monitoring of acetylcholine

An acetylcholine-selective electrode based on a plasticized polymeric membrane has been developed. The electrode exhibited good selectivity for acetylcholine (ACh) over choline and some common ions, low drift, and a fast response to ACh. The response was linear over an ACh concentration range of 1×10(-6) to 1×10(-3) M with a slope of 59.1±0.1 and a detection limit of 1.5×10(-7)±1.2×10(-8) M. The electrode was used to monitor enzymatic ACh hydrolysis catalyzed by acetylcholinesterase (AChE) at different substrate and enzyme concentrations. A kinetic data analysis permitted the determination of the Michaelis-Menten constant of the enzymatic hydrolysis and AChE activity in the range of 2×10(-5) to 3.8×10(-1)U ml(-1).     

孢悬液浓度和宿主体型大小对球孢白僵菌对松墨天牛幼虫的致病力的影响

【目的】球孢白僵菌Beauveria bassiana是一种被广泛用于害虫生物防治的生防菌。本研究探讨了孢悬液浓度和宿主体型大小对球孢白僵菌对松墨天牛Monochamus alternatus 幼虫的致病力的影响,旨在为松墨天牛的生物防治提供科学基础。【方法】分别用0.5% 吐温-80(CK)以及1×10⁵, 1×10⁶, 1×10⁷, 1×10⁸和1×10⁹孢子/mL的球孢白僵菌孢悬液接种松墨天牛4龄幼虫,统计接种后15 d内幼虫死亡率和染菌率。同时用最佳浓度(1×10⁹孢子/mL)的球孢白僵菌孢悬液接种体型大小分别为100~150, 200~220, 300~320, 400~420, 500~520和600~650 mg/头的松墨天牛幼虫,测定接种后20 d内幼虫的死亡率和染菌率。【结果】接种1×10⁵~1×10⁹孢子/mL的球孢白僵菌后,松墨天牛4龄幼虫起初活动自如,后在头部出现烧灼状伤并且体色逐渐变红,最后周身长满菌丝。不同浓度下,随球孢白僵菌孢子浓度升高,松墨天牛4龄幼虫校正死亡率和校正染菌率增加。接种1×10⁶~1×10⁹孢子/mL球孢白僵菌孢悬液15 d的松墨天牛4龄幼虫累计校正死亡率均可达到100%,1×10⁷, 1×10⁸和1×10⁹孢子/mL浓度下,松墨天牛达到100%校正死亡率所需时间最少。接种0 (CK), 1×10⁵, 1×10⁶, 1×10⁷, 1×10⁸和1×10⁹孢子/mL球孢白僵菌孢悬液的松墨天牛4龄幼虫校正染菌率在第15天分别为0, 20.00%, 86.67%, 90.00%, 96.67%和100.00%,表现为白僵菌孢子浓度越高,染菌率越高。1×10⁹孢子/mL的接种浓度下,松墨天牛幼虫个体越大,天牛幼虫死亡率和染菌率越高。表现在第20天时,体型大小为100~150, 200~220, 300~320, 400~420, 500~520和600~650 mg/头的幼虫的死亡率分别为76.67%, 76.67%, 66.67%, 93.33%, 100.00%和100.00%,染菌率分别为60.00%, 63.33%, 60.00%, 86.67%, 96.67%和100.00%。【结论】球孢白僵菌悬浮液浓度对松墨天牛幼虫的死亡和侵染有显著影响,表现为随孢子浓度的增加而增加;同时,松墨天牛幼虫个体越大,死亡率和染菌率越高。研究结果对开展利用球孢白僵菌防治松墨天牛具重要借鉴和指导意义。     

青蒿素及其类似物抗疟构效关系的DFT研究

为了从原子水平上揭示青蒿素及其类似物的结构与抗疟活性之间的关系,运用密度泛函理论DFT方法,在B3LYP/6-31G*水平上对青蒿素及其类似物二氢青蒿素、蒿甲醚和青蒿琥酯的结构和性质进行了理论计算。从分子的平衡构型、Wiberg键级、溶剂化能、偶极矩和静电势等方面分析了青蒿素及其类似物的抗疟构效关系。结果表明,青蒿素及其类似物结构中七元环上的过氧桥键、醚氧键以及六元环上的内酯结构是其抗疟作用的关键活性位,过氧桥键处负的静电势越多,青蒿素与血红素的相互作用越强,分子的抗疟活性越强。理论预测四个药物分子的抗疟活性顺序为:青蒿素<二氢青蒿素<蒿甲醚<青蒿琥酯,与实验活性结果一致。     

Association of common variants in TNFRSF13B, TNFSF13, and ANXA3 with serum levels of non-albumin protein and immunoglobulin isotypes in Japanese

We performed a genome-wide association study (GWAS) on levels of serum total protein (TP), albumin (ALB), and non-albumin protein (NAP). We analyzed SNPs on autosomal chromosomes using data from 9,103 Japanese individuals, followed by a replication study of 1,600 additional individuals. We confirmed the previously- reported association of GCKR on chromosome 2p23.3 with serum ALB (rs1260326, P(meta) = 3.1 × 10(-9)), and additionally identified the significant genome-wide association of rs4985726 in TNFRSF13B on 17p11.2 with both TP and NAP (P(meta) = 1.2 × 10(-14) and 7.1 × 10(-24), respectively). For NAP, rs3803800 and rs11552708 in TNFSF13 on 17p13.1 (P(meta) = 7.2 × 10(-15) and 7.5 × 10(-10), respectively) as well as rs10007186 on 4q21.2 near ANXA3 (P(meta) = 1.3 × 10(-9)) also indicated significant associations. Interestingly, TNFRSF13B and TNFSF13 encode a tumor necrosis factor (TNF) receptor and its ligand, which together constitute an important receptor-ligand axis for B-cell homeostasis and immunoglobulin production. Furthermore, three SNPs, rs4985726, rs3803800, and rs11552708 in TNFRSF13B and TNFSF13, were indicated to be associated with serum levels of IgG (P<2.3 × 10(-3)) and IgM (P<0.018), while rs3803800 and rs11552708 were associated with IgA (P<0.013). Rs10007186 in 4q21.2 was associated with serum levels of IgA (P = 0.036), IgM (P = 0.019), and IgE (P = 4.9 × 10(-4)). Our results should add interesting knowledge about the regulation of major serum components.     

Antimalarial activity of thioacridone compounds related to the acronycine alkaloid

A series of thioacridone compounds that were previously shown to have DNA binding interaction, were screened for antimalarial activity. The new compounds were assessed for in vitro antimalarial activity against a chloroquine sensitive (D10) strain of the malaria parasite Plasmodium falciparum, using a lactate dehydrogenase (PfLDH) assay. In the series, the IC(50) values ranged from 0.4 to 27 microg/ml. 1-(2-Dimethylaminoethylamino)-9(10H)-thioacridone was found to be the most potent against P. falciparum (D10) with an IC(50) value of 0.4 microg/ml. This compound was also evaluated against a South African chloroquine resistant (RSA 11) P. falciparum strain and was found to have an IC(50) value of 1 microg/ml, compared with 0.16 microg/ml for chloroquine. Quantitative structure-activity relationships of this series were also investigated and a multiple linear regression r(2) of 0.58 was found for the best fit equation. The most potent compound, 1-(2-dimethylaminoethylamino)-9(10H)-thioacridone, was docked into the chloroquine binding site of PfLDH and it was found that the slightly lower activity of this compound, compared with chloroquine, is likely due to steric interference within a restricted binding pocket.     

Effect of artemisinin (qinghaosu) and chloroquine on drug-sensitive and drug-resistant strains of Plasmodium falciparum malaria: use of [2,8-3H]adenosine as an alternative to [G-3H]hypoxanthine in the assessment of in vitro antimalarial activity

Using [G-3H]hypoxanthine uptake as a radioactive indicator for the growth of malarial parasites, we measured the antimalarial activity of artemisinin (Qinghaosu, QHS) against FCMSU1/Sudan strain (chloroquine-sensitive strain) and FCB K+ strain (chloroquine-resistant strain) of Plasmodium falciparum in continuous culture in vitro. The 50% inhibitory concentrations (IC50) for QHS against FCMSU1/Sudan strain and FCB K+ strain were 2.8 X 10(-8) and 3.0 X 10(-8) M, respectively. On the contrary, the response of the two strains to chloroquine was quite different. The IC50 for chloroquine against FCMSU1/Sudan strain was 5.6 ng/ml, whereas that for the FCB K+ strain was 65.6 ng/ml. Therefore, QHS did not appear to exhibit any cross-resistance with chloroquine. If [2,8-3H]adenosine was used as a radioactive precursor instead of [G-3H]hypoxanthine for the determination of antimalarial activity, virtually identical results were obtained. Therefore, [2,8-3H]adenosine can be used as an alternative to [G-3H]hypoxanthine for the assessment of antimalarial action.     

A small library of trisubstituted pyrimidines as antimalarial and antitubercular agents

A small library of 20 trisubstituted pyrimidines were synthesized and evaluated for their in vitro antimalarial and antitubercular activities. Out of the total screened compounds, 16 compounds have shown in vitro antimalarial activity against Plasmodium falciparum in the range of 0.25-2microg/mL and 8 compounds have shown antitubercular activity against Mycobacterium tuberculosis H(37)Ra, at a concentration of 12.5microg/mL.     

Regional variation in lytic and lysogenic viral infection in the southern ocean and its contribution to biogeochemical cycling

Lytic and lysogenic viral infection was investigated throughout the Southern Ocean at sites spanning the sub-Antarctic zone, the Antarctic Circumpolar Current, and an Antarctic continental sea. Higher lytic virus activity was recorded in the more productive sub-Antarctic zone than in the iron-limited waters of the Antarctic Circumpolar Current during two transects. Reduced lytic viral activity in the Antarctic Circumpolar Current was combined with a shift toward lysogenic infection, probably resulting from the lower concentration of potential prokaryotic hosts. Superimposed on this variation, lytic viral production was lower in a transect completed in the Drake Passage in autumn (1.8 × 10(8) to 1.5 × 10(9) liter(-1) day(-1)) than over the Greenwich Meridian during summer (5.1 × 10(8) to 2.0 × 10(10) cells liter(-1) day(-1)), indicating that viral activity is linked to the overall seasonal fluctuations in biotic activity. Interestingly, while prokaryotic abundance was lowest in the coastal Weddell Sea, levels of bacterial and lytic viral production (4.3 × 10(8) to 1.7 × 10(10) cells liter(-1) day(-1)) in this area were similar to those of the other zones. This may explain the weak relationship between the distribution of prokaryotes and chlorophyll in the Weddell Sea, as a high turnover of prokaryotic biomass may have been stimulated by the availability of substrates in the form of viral lysate. With estimated carbon and iron releases of 0.02 to 7.5 μg liter(-1) day(-1) and 1.5 to 175.7 pg liter(-1) day(-1), respectively, viral activity in the Southern Ocean is shown to be a major contributor to satisfying the elemental requirements of microbes, notably prokaryotes in the Weddell Sea and phytoplankton in the sub-Antarctic zone.