Cucurbitacins from Bryonia cretica

From the roots of Bryonia cretica L. two new cucurbitacins, isocucurbitacins G (1) and H (2), along with three known cucrbitacins, cucurbitacins G (3), H (4), and J (5) were isolated. The structures of 1 and 2 were determined on the basis of 1D and 2D NMR spectroscopic analysis and X-ray crystallography. The relative stereochemistries of the side chains of 3–5 were also established by comparison of their NMR data and X-ray crystallography.     

Synthesis and antibacterial activity of 5-methylphenanthridium derivatives as FtsZ inhibitors

5-Methylphenanthridium derivatives were designed, synthesized and evaluated for their in vitro antibacterial activity and cell division inhibitory activity against various Gram-positive and -negative bacteria. Among them, compounds 5A2, 5B1, 5B2, 5B3, 5C1 and 5C2 displayed the best on-target antibacterial activity with an MIC value of 4 µg/mL against B. subtilis ATCC9372 and S. pyogenes PS, showing over 2-fold better activity than sanguinarine. The SARs showed that the 5-methylphenanthridium derivatives with the alkyl side chains at the 2-postion, especially the straight alkyl side chains exerted better on-target antibacterial activity.     

6-Nitro-2,3-dihydroimidazo[2,1-b][1,3]thiazoles: Facile synthesis and comparative appraisal against tuberculosis and neglected tropical diseases

As part of a quest for backups to the antitubercular drug pretomanid (PA-824), we investigated the unexplored 6-nitro-2,3-dihydroimidazo[2,1-b][1,3]-thiazoles and related -oxazoles. The nitroimidazothiazoles were prepared in high yield from 2-bromo-4-nitroimidazole via heating with substituted thiiranes and diisopropylethylamine. Equivalent examples of these two structural classes provided broadly comparable MICs, with 2-methyl substitution and extended aryloxymethyl side chains preferred; albeit, S-oxidised thiazoles were ineffective for tuberculosis. Favourable microsomal stability data for a biaryl thiazole (45) led to its assessment in an acute Mycobacterium tuberculosis mouse model, alongside the corresponding oxazole (48), but the latter proved to be more efficacious. In vitro screening against kinetoplastid diseases revealed that nitroimidazothiazoles were inactive versus leishmaniasis but showed interesting activity, superior to that of the nitroimidazooxazoles, against Chagas disease. Overall, “thio-delamanid” (49) is regarded as the best lead.     

Role of the side chain stereochemistry in the α-glucosidase inhibitory activity of kotalanol,a potent natural α-glucosidase inhibitor. Part 2

To examine the role of the side chain of kotalanol (2), a potent natural α-glucosidase inhibitor isolated from Salacia reticulata, on inhibitory activity, four diastereomers (11a–11d) with reversed configuration (S) at the C-4′ position in the side chain were synthesized and evaluated. Two of the four (11b and 11d) significantly lost their inhibitory activity against both maltase and sucrase, while the other two (11a and 11c) sustained the inhibitory activity to a considerable extent, showing distinct activity in response to the change of stereochemistry of the hydroxyls at the 5′and 6′ positions. Different activities were rationalized with reference to in silico docking studies on these inhibitors with hNtMGAM. Against isomaltase, all four analogs showed potent inhibitory activity as well as 2, and 11b and 11d exhibited enzyme selectivity.     

Antimicrobial effects of N-benzyloxycarbonyl-S-(2,4-dinitrophenyl) glutathione diesters against chloroquinine sensitive (NF54) and resistant (K1) strains of Plasmodium falciparum

N-Benzyloxycarbony-S-(2,4-dinitrophenyl)glutathione diesters have been investigated for antimalarial activity against chloroquinine sensitive (NF54) and resistant (K1) strains of P. falciparum. Both strains appear equally susceptible to inhibition by compounds 1–4, with an IC₅₀ ∼ 4.92–6.97 μM, consistent with the target of these compounds being the PfMRP transporter. Against the NF54 strain, diester derivatives containing ethyl side chains showed lower in vitro activity than those with methyl side chains 1–4, IC₅₀ ∼ 5.7–6.97 μM with the exception of compound 5 (IC₅₀ > 25 μM). The cytotoxicity of compounds with log P ∼ 3.9–5.8 were lower against the murine L6 cell line than compounds with a higher log P > 5.8 that were toxic. Overall the cytotoxicity of compounds 1–7 were lower against KB cells than against the L6 cell line with the exception of compound 4, which showed a higher relative toxicity.     

Discovery of 6-[5-(4-fluorophenyl)-3-methyl-pyrazol-4-yl]-benzoxazin-3-one derivatives as novel selective nonsteroidal mineralocorticoid receptor antagonists

In the course of our study on selective nonsteroidal mineralocorticoid receptor (MR) antagonists, a series of novel benzoxazine derivatives possessing an azole ring as the core scaffold was designed for the purpose of attenuating the partial agonistic activity of the previously reported dihydropyrrol-2-one derivatives. Screening of alternative azole rings identified 1,3-dimethyl pyrazole 6a as a lead compound with reduced partial agonistic activity. Subsequent replacement of the 1-methyl group of the pyrazole ring with larger lipophilic side chains or polar side chains targeting Arg817 and Gln776 increased MR binding activity while maintaining the agonistic response at the lower level. Among these compounds, 6-[1-(2,2-difluoro-3-hydroxypropyl)-5-(4-fluorophenyl)-3-methyl-1H-pyrazol-4-yl]-2H-1,4-benzoxazin-3(4H)-one (37a) showed highly potent in vitro activity, high selectivity versus other steroid hormone receptors, and good pharmacokinetic profiles. Oral administration of 37a in deoxycorticosterone acetate-salt hypertensive rats showed a significant blood pressure-lowering effect with no signs of antiandrogenic effects.     

Synthesis and antibacterial activity of 7-(1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazin-7-yl) quinolones

A novel series of 7-(1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazin-7-yl) quinolones has been designed and synthesized in which the heterocyclic side chain is attached to the quinolone core through a carbon–carbon linkage. The antibacterial activity of the compounds was determined against a panel of Gram-positive and Gram-negative pathogens. Compounds 1b and 1e, bearing an 8-methoxy group as well as unsubstituted and (3S)-methyl substituted 1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazin-7-yl side chains, respectively, demonstrated notable activity against ciprofloxacin-resistant clinical isolates of Streptococcus pneumoniae.     

Novel interleukin-5 inhibitors based on hydroxyethylaminomethyl-4H-chromen-4-one scaffold

Hydroxyethylaminomethyl-4H-chromenones were previously discovered as fairly strong IL-5 inhibitor. For determination of detail structure activity relationship, N-substituted hydroxyethylaminomethylchromenones 4a–n were prepared and evaluated for their IL-5 inhibitory activity. Shifting the hydrophobic group to nitrogen from 1-position of hydroxyethylamino moiety of hydroxyethylaminomethyl-4H-chromenones enhances the activity. The increment in bulkiness or hydrophobicity of alkyl side chain at amino group increases the activity. The same level of activity of 5-(cyclohexylmethoxy)-3-(N-benzyl-2-hydroxyethylaminomethyl)-4H-chromenone analogs regardless of hydrophobic or hydrophilic substituents at 4th position of phenyl ring might infer the existence of tunnel structure in the putative receptor for accepting these side chains.     

Manzamenones L–N,new dimeric fatty-acid derivatives from an Okinawan marine sponge Plakortis sp.

Three new polyketides, manzamenones L–N (1–3), have been isolated from an Okinawan marine sponge of the genus Plakortis. The structures of 1–3 were elucidated on the basis of spectroscopic data. Manzamenones L–N (1–3) were new dimeric fatty-acid derivatives consisting of a tetrahydroindenone with three carboxy groups and two hexadecanyl chains. Manzamenones M (2) and N (3) showed antimicrobial activity against several bacteria and fungi.     

Cytotoxicity and DNA binding property of triphenylethylene–coumarin hybrids with two amino side chains

Novel triphenylethylene–coumarin hybrids containing two amino side chains were designed and synthesized. Some of these 3,4-diphenyl coumarins, 7b–c (the double chains at 4-position on 3-,4-phenyl, respectively), and 13b–f (the double chains at 4-position on 3-phenyl and 7-position, respectively), showed a broad-spectrum and good anti-proliferative activity against five tumor cells and low cytotoxicity in osteoblast. UV–vis, fluorescence, and circular dichroism (CD) spectroscopies and thermal denaturation exhibited that compounds 7b (R = piperidinyl), 7e (R = NEt₂), and 7f (R = 4-methylpiperazinyl) had significant interactions with Ct-DNA by the intercalative mode of binding. Structure activity relationships (SARs) analysis suggested that the location of the two amino alkyl chains would play an important role both in the compounds against tumor cells proliferation and their interactions with DNA.     

Novel degraded polycyclic polyprenylated acylphloroglucinol and new polyprenylated benzophenone from Hypericum sampsonii

Norhypersampsone A (1), a novel degraded polycyclic polyprenylated acylphloroglucinol (PPAP) derivative, 3-(2-hydroxy-7-methyl-3-methyleneoct-6-enyl)-5-isoprenyl-2,4,6-trihydroxybenzophenone (2), a new polyprenylated benzophenone derivative, and nine known compounds (3–11) were isolated from Hypericum sampsonii. Their structures were elucidated by comprehensive spectroscopic techniques. Compound 1 represents a novel cyclohexenone monocyclic-PPAP formed by losing the fragment of C-2–C-4 and the side chains at C-3 and C-5 in the phloroglucinol ring. The results of the inhibitory effects of compounds 1–11 on the nitric oxide (NO) production induced by lipopolysaccharide (LPS) in RAW 264.7 macrophages showed that compounds 1, 6–8, and 10 exhibited weak activities with IC₅₀ values in the range of 20.3–37.1 μM.     

Efficiency of newly prepared thiazole derivatives against some cutaneous fungi

A series of fourteen novel synthesized arylazothiazole and arylhydrazothiazole derivatives were tested for their antifungal activity and structure-activity relationship. The activity of the compounds depends mainly on the side chains of the nucleus compound. The antifungal activity was more significant when both side chains are aromatic?>?one aromatic and one aliphatic and substituted aromatic with CH₃ or OCH₃?>?non-substituted?>?substituted aromatic with chloro- or nitro-groups. Thiazole derivatives 7a, 7c, 7e, 7f, 7?g, 7i, 7?m, and 11a showed the most effective as antifungal compounds and were comparable with fluconazole as antifungal reference drug when investigated against Candida albicans, Microsporum gypseum and Trichophyton mentagrophytes. The minimum inhibitory concentration (MIC) reached 2?µg/mL in the case of C. albicans for compounds 7a, 7b, 7c and 11a and measured 4?µg/mL in the case of M. gypseum and T. mentagrophytes for the same compounds. The minimum fungicidal concentration (MFC) for the same compounds was 4?µg/mL for C. albicans and ranged from 8 to 32?µg/mL for the other two fungi. The results revealed that compounds 7c and 11a were the most antifungal compounds against the test fungi regarding keratinase activity and ergosterol biosynthesis. The in vivo efficacy of synthesized thiazoles 7c and 11a applied at their respective MFC was more effective in the treatment of skin infection of guinea pigs previously inoculated with the test fungi as compared with fluconazole. The Molecular Operating Environment (MOE) software was used to analyze the docking poses and binding energies of compound 11a and keratinase. The computational studies supported the biological activity results.     

Two new nonacosanetriols from Ginkgo biloba sarcotesta

Two new fatty alcohols named as (7S,8R,11S)-nonacosanetriol (1) and (10R,12R,15S)-nonacosanetriol (2), along with eight known compounds including ginkgolic acid (3), hydroginkgolic acid (4), sciadopitysin (5), ginkgetin (6), isoginkgetin (7), ginkgolide A (8), ginkgolide B (9) and ginkgolide C (10) have been isolated from the petroleum ether extract of Ginkgo biloba sarcotesta. Their structures were elucidated by means of chemical and extensive spectroscopic analysis. The absolute stereochemistry of compounds 1 and 2 was elucidated on the spectroscopic analysis of the R- and S-MTPA esters. Compounds 1 and 2 exhibited slight activity of antithrombin and moderate activity of antiplatelet aggregation in vitro. This was the first report regarding the anticoagulative activities of biflavonoids in G. biloba, and isoginkgetin (7) showed significant antithrombin and antiplatelet aggregation activity.     

Pentacyclic triterpenoids and other constituents isolated from the leaves of Gambeya lacourtiana and their antibacterial activity

The phytochemical study was done on the leaves of Gambeya lacourtiana. This plant has been used in traditional medicine to treat of different ailments such as uterine heamorrhage, metritis and other vaginal infections. Chromatographic fractionation and purification on the leaves crude extract afforded lupeol acetate (1), lupenone (2), lupeol (3), taraxerol (4) stigmasterol (5), erythrodiol (6), chamaedrydiol (7), methyl pheophorbide-a (8), corosolic acid (9), tormentic acid (10), epicatechin (11) and 22-dihydrospinasterol 3-O-β-D-glucopyranoside (12). The structures of compounds 1–12 were elucidated on the basis of 1D and 2D NMR, mass spectrometric and the spectroscopic data as well as comparison with the literature. Compounds 4, 7–10 and 12 were isolated for the first time from Gambeya genus. Crude extract, fractions and compounds 6–12 were evaluated for their antibacterial activity. Methyl pheophorbide-a (8) demonstrated moderate activity against Salmonella typhi CPC with MIC values of 62.5 μg/mL. The chemophenetic significance of these compounds is also discussed.     

Synthesis and cytotoxicity evaluation of A-ring derivatives of cycloartanone

Sixteen derivatives, eight of which are new compounds, were prepared from cycloartenone (1) and cycloartanone (2), and the cytotoxic activity of 14 of these compounds, together with 1 and 2, was evaluated against a panel of four cell lines. Compound 1 was obtained from the epiphyte plant Tillandsia tenuifolia collected at Salta, Argentina. Due to chemoselectivity and regioselectivity problems observed in the reactions of compound 1, this substance was hydrogenated to compound 2. The attempted transformations were focused on ring A of the cited triterpenes with the aim to verify previous structure-activity relationships obtained from related compounds. The cytotoxicity results of the derivatives showed that only the diosphenol 13 displayed significant activity against all the tested cell lines. These results show that an oxidized side chain, for example an ether bridge between the side chain and ring D, is necessary for the cytotoxic activity of cycloartane derivatives.     

Structure-based rational design,synthesis and antifungal activity of oxime-containing azole derivatives

In an attempt to find novel azole antifungal agents with improved activity and broader spectrum, computer modeling was used to design a series of new azoles with piperidin-4-one O-substituted oxime side chains. Molecular docking studies revealed that they formed hydrophobic and hydrogen-bonding interactions with lanosterol 14α-demethylase of Candida albicans (CACYP51). In vitro antifungal assay indicates that most of the synthesized compounds showed good activity against tested fungal pathogens. In comparison with fluconazole, itraconazole and voriconazole, several compounds (such as 10c, 10e, and 10i) show more potent antifungal activity and broader spectrum, suggesting that they are promising leads for the development of novel antifungal agents.     

Furanocoumarins from the twigs of Ficus chlamydocarpa (Moraceae)

Two furanocoumarin derivatives, 3-methoxypsoralen (1) and 3,5-dimethoxypsoralen (2), along with nine known compounds, friedelinol (3), 3-oxo-11β-hydroxyoleanan-12-ene (4), lupeol (5), taraxer-3-one (6), a mixture of β-sitosterone (7a) and stigmast-4,22-dien-3-one (7b), ergosterol (8), 9,19-cyclolanost-3-one-24,25-diol (9), oleanan-12-ene-3,11-dione (10), and β-sitosterol 3-O-β-D-glucopyranoside (11) were isolated from the twigs of Ficus chlamydocarpa. Their structures were established by NMR spectroscopic analyses and HRESIMS. The structure of 1 was further confirmed from its single crystal X-ray diffraction. The crude extract, fractions and some isolated compounds were assessed for their preliminary antibacterial activity and cytotoxicity. One of the fractions (FB-B3) exhibited inhibition against the bacterial strain Pseudomonas agarici and induced a remarkable cytotoxic activity toward the human cervix carcinoma cell line KB-3-1 (IC₅₀ 0.166 mg/mL), and compounds 1, 6, and 7 showed moderate antibacterial activity against Bacillus subtilis and Micrococcus luteus.     

New unsaturated fatty acid and other chemical constituents from the roots of Cola rostrata K. Schum. (Malvaceae)

Phytochemical investigation of the roots of Cola rostrata K. Schum. led to the isolation of a new unsaturated fatty acid, named rostratanic acid (1), together with fourteen known compounds, lignoceric acid, friedelan (7), friedelanone (8), bauerenol (3), lupeol (4), herranone (9), acotatarone A (11), betulinic acid (6), betulin (5), nonanedioc acid (2), arjunolic acid (10) stigmasterol, β−sitosterol, and β−sitosterol-3-O-β-D-glucopyranoside. The structure of the new compound as well as those of the known compounds were established by means of spectroscopic methods: NMR analysis (¹H and ¹³C NMR, ¹H–¹H–COSY, HSQC and HMBC) and high-resolution mass spectrometry (HR-ESI-MS), and by comparison with previously reported data. Two of those known compounds were modified chemically to afford three new derivatives. All those compounds were tested for their cytotoxic activity against the human cervix carcinoma KB-3-1 cells and their antibacterial activity against Escherichia coli, Salmonella enterica, Pseudomonas aeruginosa and Staphylococcus aureus. Although the crude extract gave weak antibacterial activity, none of the isolated compounds showed antibacterial activity, and, only the prenylated derivative showed weak cytotoxicity. In addition, the chemotaxonomic significance of the species Cola rostrata is discussed.     

Design,synthesis, and anti-tumor activities of novel triphenylethylene–coumarin hybrids,and their interactions with Ct-DNA

Novel triphenylethylene–coumarin hybrid derivatives containing different amounts of amino side chains were designed and synthesized in good yields under microwave radiation. The derivatives 5b–d which possessed two amino side chains (except morpholinyl) showed a broad-spectrum and good anti-proliferative activity against five tumor cells and low cytotoxicity in osteoblast. UV–vis, fluorescence, and circular dichroism (CD) spectroscopies and thermal denaturation exhibited that compounds 10c, 5c, and 13c bearing amino side chain (except morpholinyl) on 4-phenyl had significant interactions with Ct-DNA by the intercalative mode of binding. Structure–activity relationships (SARs) analysis suggested that the amino alkyl chain would play an important role both in the compounds against tumor cells proliferation and their interactions with DNA.