Compounds from Kadsura angustifolia with anti-HIV activity

Four new cycloartane triterpenoids, angustific acid A (1), angustific acid B (2), angustifodilactone A (3) and angustifodilactone B (4) were isolated from the branches of Kadsura angustifolia together with six known compounds, micranoic acid B (5), nigranoic acid (6), schisandrin (7), schisantherin D (8), interiotherin B (9), schisantherin B (10). Their structures were established on the basis of extensive spectroscopic data analyses and comparison with spectroscopic data reported. Compound 1, characterized by the presence of a C-16/C-17, C-20/C-21 conjugated diene and a C-1/C-7 ester bridge formed in rings A and B, provided a novel structural skeleton for 3,4-secocycloartane triterpenoid derivatives. In addition, the anti-HIV activities of these compounds were determined in infected C8166 cells, and it was found that angustific acid A (1) exhibited the most potent anti-HIV activity with an EC₅₀ value of 6.1 μg/mL and a therapeutic index of more than 32.8.     

Three new isoflavonoids with antioxidant properties from Ptycholobium contortum (N.E.Br.) Brummitt (Leguminosae)

Two new pterocarpans, seputhecarpan A (1) and B (2) and a new isoflavanone seputheisoflavone (3) were isolated from the roots of Ptycholobium contortum. Seputhecarpan A and B were identified respectively as 9-hydroxylated and 9,16-dihydroxylated pterocarpans possessing a linear (C-2/C-3) isopropenyldihydrofuran substituent and seputheisoflavone as 5′-α,α-dimethylallyl-4′,5,7-trihydroxy-2′-methoxyisoflavanone. In addition, four known compounds, genistein, isoliquiritigenin, thonningiol and (−)-medicarpin were isolated. Their structures were elucidated using intensive 1D and 2D NMR spectroscopies, CD and MS data. The new compounds were assayed for their antimicrobial, α-glucosidase and antioxidant activities. If the antimicrobial and α-glucosidase inhibitory properties were weak, all the tested compounds exhibited antioxidant activities and seputhecarpan A (1) was most effective as an antioxidant with an EC50 value of 0.030 mg/ml.     

Novel nucleosides as potent influenza viral inhibitors

Influenza virus infection constitutes a significant health problem in need of more effective therapies. We have recently identified ((2R,3S,4R,5R)-3-acetoxy-5-(4-benzamido-2-oxopyrimidin-1(2H)-yl)-4-fluoro-3,4-dimethyl-tetrahydrofuran-2-yl) methyl benzoate (18c) as a potent influenza virus inhibitor. We now here report the synthesis and evaluation of a series of C-3′ modified ribose nucleosides. These novel compounds were prepared, primarily by taking known ((2R,3R,4R)-3-benzoyloxy-4-fluoro-4-methyl-5-oxo-tetrahydrofuran-2-yl)methyl benzoate (1) and converting it in to C-3 keto sugar (7), reacting C-3 keto group with methyl magnesium bromide, followed by coupling these sugars with purine and pyrimidine bases. Anti influenza viral activity was determined by screening against both A and B viral strains.     

Cytotoxicity and inhibition of DNA topoisomerase I of polyhydroxylated triterpenoids and triterpenoid glycosides

Cytotoxicity and inhibition on human DNA topoisomerase I (TOP1) and II (TOP2) of 74 plant-originated triterpenoids and triterpenoid glycosides were investigated. The cytotoxic compounds are primarily polyhydroxylated oleananes (GI₅₀ of A549: 1.0–10.19 μM). Sixteen cytotoxic aesculiosides isolated from Aesculus pavia inhibited TOP1 catalytic activity by interacting directly with the free enzyme and preventing the formation of the DNA–TOP1 complex. Interestingly, hydrolysis of six active aesculiosides (1, 4, 6, 8, 10, and 23) lost their TOP1 activities but enhanced their cytotoxicities. None of the test compounds showed any activity against TOP2. Structure–activity relationship (SAR) investigations indicated that cytotoxic oleananes required at least one angeloyl moiety at either C-21 or C-22 but the sugar moiety at C-3 may decrease their cytotoxicities. An angeloyl or tigeloyl group at C-21 is required for oleananes to bind the free TOP1 enzyme although the type and length of acyl moiety at C-22 also affects their activity. However, sugar moiety at C-3 is necessary for their TOP1 activities.     

Cycloartane-type triterpenes from Euphorbia fischeriana stimulate human CYP3A4 promoter activity

A chemical study of the roots of Euphorbia fischeriana resulted in the isolation of seven triterpenes (1–7), including two new compounds: (24R,S)-3β-24,31-epoxy-24-methylcycloartane (1) and (24R,S)-3β,31-dihydroxy-24-methoxy-24-methylcycloartane (2). Their structures were elucidated through extensive spectroscopic analyses. Cycloartanes 1–4 showed significant human CYP3A4 promoter activity through a series of luciferase reporter assays. Of these compounds, 3 and 4 activated the pregnane X receptor (PXR) and induced CYP3A4 mRNA expression in human primary hepatocytes. However, despite showing the most potent human CYP3A4 promoter activity via a PXR-independent pathway, 2 did not affect CYP3A4 mRNA expression in human primary hepatocytes. This difference is correlated to substitutions in C-24 and C-25 of the cycloartane structure.     

Isoswinholide B and swinholide K,potently cytotoxic dimeric macrolides from Theonella swinhoei

Chemical investigation of an Indonesian specimen of Theonella swinhoei afforded the new dimeric macrolides isoswinholide B (5) and swinholide K (6), along with the known swinholides A (1), B (2) and D (3) and isoswinholide A (4). Isoswinholide B showed an unprecedented 21/19′ lactonization pattern, while swinholide K included an sp² methylene attached at C-4 and an additional oxymethine group at C-5, whose configuration has been determined through application of J-based configuration analysis. The isolated swinholides (1–6), with the exception of isoswinholide B, showed a cytotoxic activity on HepG2 (hepatocarcinoma cell line) in the nanomolar range.     

Novel imidazo[2,1-b][1,3,4]thiadiazole (ITD) hybrid compounds: Design,synthesis, efficient antibacterial activity and antioxidant effects

In this study, novel imidazo[2,1-b][1,3,4]thiadiazole (ITD) compounds were synthesized and their antimicrobial and antioxidant capacity was examined. The C-2 position of the ITD structure was fixed with the 3,4-hydroxybenzene ring and the properties of the two series of compounds obtained by phenyl or 4-chlorophenyl in the C-6 position were compared. In the formation of these series, new properties were determined by the addition of different pharmacophore to the target product by binding of the groups known in the literature from the C-5 position to the structure. In the study, it was seen that the compounds 4a, 4b, 5a, 5b, 7f, 10, 12 and 13 had very high anti-tuberculosis activities at low concentrations, 3b was found to exhibit moderate activity while other synthesis compounds exhibited moderate activity. In addition, it showed activity against gram positive and negative bacteria. In the determination of the antioxidant capacities of the newly synthesized compounds by FRAP and DPPH methods, the compounds showing activity were found to be 2, 3a, 3b, 6c, 9, 11 and 13.The structures of all synthesized compounds were solved by spectroscopic methods such as FT-IR, ¹H NMR, ¹³C NMR and mass.     

Biaryl purine derivatives as potent antiproliferative agents: Inhibitors of cyclin dependent kinases. Part I

The introduction of an aryl ring onto the 4-position of the C-6 benzyl amino group of the Cdk inhibitor roscovitine (2), maintained the potent Cdk inhibition demonstrated by roscovitine (2) as well as greatly improving the antiproliferative activity. A series of C-6 biarylmethylamino derivatives was prepared addressing modifications on the C-6 biaryl rings, N-9 and C-2 positions to provide compounds that displayed potent cytotoxic activity against tumor cell lines. In particular, derivative 21h demonstrated a >750-fold improvement in the growth inhibition of HeLa cells compared to roscovitine (2).     

Synthesis of new sugar derivatives and evaluation of their antibacterial activities against Mycobacterium tuberculosis

A series of sugar derivatives (1–13) were synthesized and evaluated for antibacterial activity against Mycobacterium tuberculosis (MTB), especially multi-drug resistant (MDR) MTB, and the structure–activity relationships of these compounds were studied. The results showed that the compound OCT313 (2-acetamido-2deoxy-β-d-glucopyranosyl N,N-dimethyldithiocarbamate) (4) exhibited significant in vitro bactericidal activity, and that the dithiocarbamate group at C-1 position of the glucopyranoside ring was requisite for the antibacterial activity.     

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.     

Phragmalin-type limonoids with NF-κB inhibition from Chukrasia tabularis var. velutina

Chemical investigation on Chukrasia tabularis var. velutina led to the identification of eight new phragmalin-type limonoids (1–8), as well as 20 known analogues. Compounds 1–4 are a rare class of C-15-acyl phragmalin-type limonoids, and particularly compounds 2–4 also possess a δ-lactone ring formed between C-16 and C-30. All the isolates were evaluated for inhibitory effects on NF-κB production, and four of which showed significant inhibitions.     

Synthesis and biological evaluation of 4-(1,2,3-triazol-1-yl)coumarin derivatives as potential antitumor agents

In this research, a series of 4-(1,2,3-triazol-1-yl)coumarin conjugates were synthesized and their anticancer activities were evaluated in vitro against three human cancer cell lines, including human breast carcinoma MCF-7 cell, colon carcinoma SW480 cell and lung carcinoma A549 cell. To increase the biological potency, structural optimization campaign was conducted focusing on the C-4 position of 1,2,3-triazole and the C-6, C-7 positions of coumarin. In addition, to further evaluate the role of 1,2,3-triazole and coumarin for antiproliferative activity, 9 compounds possessing 4-(piperazin-1-yl)coumarin framework and 3 derivatives baring quinoline core were also synthesized. By MTT assay in vitro, most of the compounds display attractive antitumor activities, especially 23. Further flow cytometry assays demonstrate that compound 23 exerts the antiproliferative role through arresting G₂/M cell-cycle and inducing apoptosis.     

Rational design and synthesis of topoisomerase I and II inhibitors based on oleanolic acid moiety for new anti-cancer drugs

Semisynthetic reactions were conducted on oleanolic acid, a common plant-derived oleanane-type triterpene. Ten rationally designed derivatives of oleanolic acid were synthesized based on docking studies and tested for their topoisomerase I and IIα inhibitory activity. Semisynthetic reactions targeted C-3, C-12, C-13, and C-17. Nine of the synthesized compounds were identified as new compounds. The structures of these compounds were confirmed by spectroscopic methods (1D, 2D NMR and MS). Five oleanolic acid analogues (S2, S3, S5, S7 and S9) showed higher activity than camptothecin (CPT) in the topoisomerase I DNA relaxation assay. Four oleanolic acid analogues (S2, S3, S5 and S6) showed higher activity than etoposide in a topoisomerase II assay. The results indicated that the C12–C13 double bond of the oleanolic acid skeleton is important for the inhibitory activity against both types of topoisomerases, while insertion of a longer chain at either position 3 or 17 increases the activity against topoisomerases by various degrees. Some of the synthesized compounds act as dual inhibitors for both topoisomerase I and IIα.     

A novel series of 11-O-carbamoyl-3-O-descladinosyl clarithromycin derivatives bearing 1,2,3-triazole group: Design,synthesis and antibacterial evaluation

A series of novel 11-O-carbamoyl-3-O-descladinosyl clarithromycin derivatives bearing the 1,2,3-triazole group were designed, synthesized, and evaluated for their in vitro antibacterial activity. The antibacterial results indicated that most of the target compounds not only increased their activity against resistant bacterial strains, but also partially retained the activity against sensitive bacterial strains compared with clarithromycin. Among them, 13d had the best antibacterial activity against resistant strains, including Streptococcus pneumoniae B1 expressing the ermB gene (16 µg/mL), Streptococcus pneumoniae AB11 expressing the mefA and ermB genes (16 µg/mL) and Streptococcus pyogenes R1 (16 µg/mL), showing >16, 8 and 16-fold higher activity than that of CAM, respectively. Moreover, 13d and 13g exhibited the best antibacterial activity against sensitive bacterial strains, including Staphylococcus aureus ATCC25923 (4 µg/mL) and Bacillus Subtilis ATCC9372 (1 µg/mL). The MBC results showed that the most promising compounds 13d and 13g exhibited antibacterial activity through bacteriostatic mechanism, while the time-kill kinetic experiment revealed bactericidal kinetics of 13g from microscopic point of view. In vitro antibacterial experiments and molecular docking results further confirmed that it was feasible to our initial design strategy by modifying the C-3 and C-11 positions of clarithromycin to increase the activity against resistant bacteria.     

Evaluation of in vitro anticancer activity of sphaeropsidins A–C,fungal rearranged pimarane diterpenes,and semisynthetic derivatives

Sphaeropsidins A (1), B (7) and C (10), three fungal phytotoxins, unrearranged pimarane diterpenes produced by Diplodia cupressi and 10 semisynthetic derivatives were evaluated for their in vitro anticancer activities. Among these 13 compounds, sphaeropsidin A and two derivatives (2 and 6) thereof display 50% growth-inhibitory concentration in the low micromolar range for all cell lines analyzed. Structure activity relationship paralleled the phytopathogenic and antimicrobial ones except regarding the vinyl group at C-13 that does not seems to be required as it is for their antipathogenic activity.     

Design,synthesis and cytotoxicity of cell death mechanism of rotundic acid derivatives

In the present investigation, 16 new rotundic acid (RA) derivatives modified at the C-3, C-23 and C-28 positions were synthesized. The cytotoxicities of the derivatives were evaluated against HeLa, A375, HepG2, SPC-A1 and NCI-H446 human tumor cell lines by MTT assay. Among these derivatives, compounds 4–7 exhibited stronger cell growth inhibitory than RA and compound 4 was found to be the best inhibition activity on five human tumor cell lines with IC₅₀ <10 μM. The apoptosis mechanism of compound 4 in HeLa cells was investigated by western blot analysis. The results indicated that compound 4 could induce apoptosis through increasing protein expression of cleaved caspase-3 and Bax, and decreasing protein expression of Bcl-2. In summary, the present work suggests that compound 4 might serve as an effective chemotherapeutic candidate.     

Loranthin: A new polyhydroxylated flavanocoumarin from Plicosepalus acacia with significant free radical scavenging and antimicrobial activity

A new flavanocoumarin, loranthin (1) together with catechin (2), quercetin (3) rutin (4), gallic acid (5) and methyl gallate (6) were isolated from Plicosepalus acacia. Loranthin possesses the rare flavanocoumarin skeleton in which the flavan and coumarin moieties are linked via C-7/C-8 of both moieties. The flavan moiety in 1 was found to be catechin, while a 3,5,6,7-tetrahydroxycoumarin fragment represented the other moiety in 1. The structures of the isolated compounds were established based on different spectroscopic data including HRFABMS, 1D and 2D NMR (COSY, HSQC, and HMBC). The free radical scavenging activities of different extracts and pure compounds were determined using DPPH reagent and all the tested samples revealed significant activities with variable percent. Loranthin exhibited a 38.4% inhibition in the free radical scavenging assay. The antimicrobial activity of loranthin was evaluated against several pathogen and loranthin displayed significant effect against Staphylococcus aureus. Moreover, the inhibition activity of the compounds against several disease-relevant protein kinases were also evaluated and discussed.     

Antiparkinsonian activity of some 9-N-, O-, S- and C-derivatives of 3-methyl-6-(prop-1-en-2-yl)cyclohex-3-ene-1,2-diol

Earlier it was found, that (1R,2R,6S)-3-methyl-6-(prop-1-en-2-yl)cyclohex-3-ene-1,2-diol (1) possess high antiparkinsonian activity. The N-, O-, S- and C-derivatives at the C-9 position of diol 1 were synthesized in this work. The antiparkinsonian activity of these compounds was studied in MPTP mice models. As a rule, the introduction of substituents containing nitrogen atoms at the C-9 position led to a considerable decrease or loss of antiparkinsonian activity. A derivative of 2-aminoadamantane 8 significantly decreased the locomotor activity time, thus enhancing the symptoms of the parkinsonian syndrome. However the introduction of butyl or propylthio substituents at the C-9 position of diol 1 did not diminish the antiparkinsonian activity comparing to parent compound. This information is important when choosing a route for immobilization of compound 1 to find possible targets.     

Neo-clerodane diterpenes from Ajuga turkestanica

The ethyl acetate extract of the aerial parts of Ajuga turkestanica afforded 6 neo-clerodane diterpenes, including two novel compounds, 14,15-dihydroajugachin B (1) and 14-hydro-15-methoxyajugachin B (2), in addition to the known diterpenoids chamaepitin (3), ajugachin B (4), ajugapitin (5) and lupulin A (6). Structures were established through exhaustive NMR spectroscopic analysis and chemical transformation in the case of 1. The full ¹H and ¹³C NMR assignment of the C-15 R and S configurations of 14-hydro-15-methoxyajugachin B and chamaepitin were elucidated.     

A new secoiridoid glycoside and a new sesquiterpenoid glycoside from Valeriana jatamansi with neuroprotective activity

A new secoiridoid glycoside, isopatrinioside (1) and a new sesquiterpenoid glycoside, valeriananoid F (2), together with nine known compounds, were isolated from the roots of Valeriana jatamansi. Their structures were elucidated on the basis of spectroscopic analysis. Compound 1 was an unusual monocyclic iridoid glycoside ring-opened between C-1 and C-2 produced by the cleavage of the pyran ring. Of the eleven isolates, compounds 1 and 4 exhibited moderate neuroprotective effects against CoCl₂-induced neuronal cell death in PC12 cells.