Identification of 1,6-dihydropyrazolo[4,3-c]carbazoles and 3,6-dihydropyrazolo[3,4-c]carbazoles as new Pim kinase inhibitors

New 1,6-dihydropyrazolo[4,3-c]carbazoles and 3,6-dihydropyrazolo[3,4-c]carbazoles were prepared and evaluated for their Pim kinase inhibitory potencies as well as their antiproliferative activities toward two prostatic cancer cell lines. Pyrazolocarbazole 15a was found to be a potent Pim kinase modulator with inhibitory potency toward the three isoforms. Compound 6c strongly inhibited Pim-3 with weaker effect toward Pim-1 and Pim-2, and thus could be used as an interesting molecular tool to study Pim-3 biological functions.     

Pim kinase inhibitory and antiproliferative activity of a novel series of meridianin C derivatives

A novel series of meridianin C derivatives substituted at C-5 position were prepared. These derivatives were tested for their kinase inhibitory potencies against all three family members of the pim kinases (Pim-1, Pim-2 and Pim-3). In addition, their antiproliferative activity towards three human leukemia cell lines as MV4-11, Jurkat clone E6-1 and K562 has been evaluated. Structure activity relationships at C-3 and C-5 positions of indole were performed to better understand the mechanism behind the enhanced potency. Compound 7f, the most active compound of the series showed a single-digit nanomolar IC₅₀ with selectivity towards Pim-1 kinase.     

Kinase inhibitory potencies and in vitro antiproliferative activities of N-10 substituted pyrrolo[2,3-a]carbazole derivatives

Development of potent and selective Pim kinase inhibitors has recently emerged as an important field for the design of new anti-cancer drugs. We report the synthesis of new N-10-substituted pyrrolo[2,3-a]carbazole derivatives and their evaluation as Pim kinase inhibitors. Moreover, in vitro antiproliferative activity of these compounds was evaluated toward a human fibroblast primary culture and three human solid cancer cell lines (PA1, PC3 and DU145). Compounds 3, 7 and 10 showed inhibitory potencies toward Pim-1 and Pim-3 in the nanomolar range. Additionally, dimethylamino analog 10 also demonstrated interesting sub-micromolar antiproliferative activities toward the cell lines tested.     

Synthesis of pyrazolo[4,3-a]phenanthridines,a new scaffold for Pim kinase inhibition

A new series of nitro or amino substituted pyrazolo[4,3-a]phenanthridines was synthesized in 6 steps from 5-bromo-6-nitroindazole. The evaluation of their inhibitory potency toward Pim kinases demonstrated that the nitro series could be considered as an interesting starting point for the development of new Pim kinase inhibitors, especially Pim-3. A preferential binding mode was suggested by molecular modeling experiments for nitro series and Pim-1/Pim-3 ATP-binding sites. Moreover, the most active compounds exhibited antiproliferative activities toward PC3 cells in the micromolar range.     

Identification of pyrrolo[2,3-g]indazoles as new Pim kinase inhibitors

The synthesis and Pim kinase inhibition potency of a new series of pyrrolo[2,3-g]indazole derivatives is described. The results obtained in this preliminary structure–activity relationship study pointed out that sub-micromolar Pim-1 and Pim-3 inhibitory potencies could be obtained in this series, more particularly for compounds 10 and 20, showing that pyrrolo[2,3-g]indazole scaffold could be used for the development of new potent Pim kinase inhibitors. Molecular modeling experiments were also performed to study the binding mode of these compounds in Pim-3 ATP-binding pocket.     

The design,synthesis and structure-activity relationships associated with C28 amine-based betulinic acid derivatives as inhibitors of HIV-1 maturation

The design and synthesis of a series of C28 amine-based betulinic acid derivatives as HIV-1 maturation inhibitors is described. This series represents a continuation of efforts following on from previous studies of C-3 benzoic acid-substituted betulinic acid derivatives as HIV-1 maturation inhibitors (MIs) that were explored in the context of C-28 amide substituents. Compared to the C-28 amide series, the C-28 amine derivatives exhibited further improvements in HIV-1 inhibitory activity toward polymorphisms in the Gag polyprotein as well as improved activity in the presence of human serum. However, plasma exposure of basic amines following oral administration to rats was generally low, leading to a focus on moderating the basicity of the amine moiety distal from the triterpene core. The thiomorpholine dioxide (TMD) 20 emerged from this study as a compound with the optimal antiviral activity and an acceptable pharmacokinetic profile in the C-28 amine series. Compared to the C-28 amide 3, 20 offers a 2- to 4-fold improvement in potency towards the screening viruses, exhibits low shifts in the EC₅₀ values toward the V370A and ΔV370 viruses in the presence of human serum or human serum albumin, and demonstrates improved potency towards the polymorphic T371A and V362I virus variants.     

Demethylbellidifolin isolated from Swertia bimaculate against human carboxylesterase 2: Kinetics and interaction mechanism merged with docking simulations

In this study, forty-nine kinds of traditional Chinese medicines (TCMs) were evaluated for their inhibitory activities against human carboxylesterase 2 (HCE 2) using a human liver microsome (HLM) system. Swertia bimaculata showed significant inhibition on HCE 2 at 10 μg/mL among forty-nine kinds of TCMs. The extract of Swertia bimaculata was separated by preparative HPLC to afford demethylbellidifolin (1) identified by MS, ¹H NMR, and ¹³C NMR spectra. Demethylbellidifolin (1) was assayed for its inhibitory HCE 2 effect by HCE 2-mediated DDAB hydrolysis, and its potential IC₅₀ value was 3.12 ± 0.64 μM. Demethylbellidifolin (1) was assigned as a mixed-type competitive inhibitor with the inhibiton constant Ki value of 6.87 µM by Lineweaver-Burk and slope plots. Living cell imaging was conducted to corroborate its inhibitory HCE 2 activity. Molecular docking indicated potential interactions of demethylbellidifolin (1) with HCE 2 through two hydrogen bonds of the C-3 and C-5 hydroxy groups with amino acid residues Glu227 and Ser228 in the catalytic cavity, respectively.     

Synthesis and biological evaluation of pyrano[4,3-b][1]benzopyranone derivatives as monoamine oxidase and cholinesterase inhibitors

A series of eighteen pyrano[4,3-b][1]benzopyranone derivatives (1a-9b) were synthesized, and structure-activity relationships of their monoamine oxidase (MAO) A and B, acetylcholinesterase (AChE), and butyrylcholinesterase (BChE) inhibitory activities were evaluated. Most of the synthesized compounds exhibited weak inhibitory activity toward MAO-A, whereas compounds 2a, 2b, 4a, 4b, 5a, 5b, 6a, 6b, 8a and 8b showed potent inhibitory activities toward MAO-B. Intriguingly, compounds 5a, 5b, and 8a showed inhibitory activities comparable to pargylin, used as a positive control for MAO-B. Substitution of butoxy at the C3 position or of chlorine at the C8 position of pyrano[4,3-b][1]benzopyranone increased the inhibitory activity of the compound toward MAO-B. The results of a molecular docking study supported this structural effect. Most of the compounds exhibited no or slight inhibitory activity toward AChE and BChE, with exo type compounds bearing a butoxy group, such as compounds 2b, 5b and 8b, showing weak but distinct inhibitory activities toward BChE. This report is the first to identify pyrano[4,3-b][1]benzopyranone derivatives as potent and selective MAO-B inhibitors. 3-Butoxy-8-chloro-pyrano[4,3-b][1]benzopyranone (5b) may be useful as a lead compound for the development of MAO-B inhibitors.     

Structure-based design of 3-aryl-6-amino-triazolo[4,3-b]pyridazine inhibitors of Pim-1 kinase

A series of substituted 3-aryl-6-amino-triazolo[4,3-b]pyridazines were identified as highly selective inhibitors of Pim-1 kinase. Initial exploration identified compound 24 as a potent, selective inhibitor, limited in its utility by poor solubility and permeability. Understanding the unusual ATP-binding site of the Pim kinases and X-ray crystallographic data on compound 24 led to design improvements in this class of inhibitor. This resulted in compound 29, a selective, soluble and permeable inhibitor of Pim-1.     

Design,synthesis and evaluation of 2,4-disubstituted pyrimidines as cholinesterase inhibitors

A group of 2,4-disubstituted pyrimidine derivatives (7a–e, 8a–e and 9a–d) that possess a variety of C-2 aliphatic five- and six-membered heterocycloalkyl ring in conjunction with a C-4 arylalkylamino substituent were designed, synthesized and evaluated as cholinesterase (ChE) inhibitors. The steric and electronic properties at C-2 and C-4 positions of the pyrimidine ring were varied to investigate their effect on ChE inhibitory potency and selectivity. The structure–activity relationship (SAR) studies identified N-benzyl-2-thiomorpholinopyrimidin-4-amine (7c) as the most potent cholinesterase inhibitor (ChEI) with an IC₅₀ = 0.33 μM (acetylcholinesterase, AChE) and 2.30 μM (butyrylcholinesterase, BuChE). The molecular modeling studies indicate that within the AChE active site, the C-2 thiomorpholine substituent was oriented toward the cationic active site region (Trp84 and Phe330) whereas within the BuChE active site, it was oriented toward a hydrophobic region closer to the active site gorge entrance (Ala277). Accordingly, steric and electronic properties at the C-2 position of the pyrimidine ring play a critical role in ChE inhibition.     

Alstiphyllanines E–H,picraline and ajmaline-type alkaloids from Alstonia macrophylla inhibiting sodium glucose cotransporter

Three new picraline-type alkaloids, alstiphyllanines E–G (1–3) and a new ajmaline-type alkaloid, alstiphyllanine H (4) were isolated from the leaves of Alstonia macrophylla together with 16 related alkaloids (5–20). Structures and stereochemistry of 1–4 were fully elucidated and characterized by 2D NMR analysis. Alstiphyllanines E and F (1 and 2) showed moderate Na⁺-glucose cotransporter (SGLT1 and SGLT2) inhibitory activity. A series of a hydroxy substituted derivatives 21–28 at C-17 of the picraline-type alkaloids have been derived as having potent SGLT inhibitory activity. 10-Methoxy-N(1)-methylburnamine-17-O-veratrate (6) exhibited potent inhibitory activity, suggesting that the presence of an ester side chain at C-17 may be important to show SGLT inhibitory activity. Structure activity relationship of alstiphyllanines on inhibitory activity of SGLT was discussed.     

Microbial transformation of glycyrrhetinic acid derivatives by Bacillus subtilis ATCC 6633 and Bacillus megaterium CGMCC 1.1741

Glycyrrhetinic acid (GA), the major bioactive pentacyclic triterpene aglycone of licorice root, was known to play a vital role in anti-ulcer, anti-depressant, anti-inflammatory, and anti-allergic. In this study, we semi-synthesized five GA derivatives by a series of chemical reactions. They were selected as substrates for the biotransformation and yielded thirteen metabolites by Bacillus subtilis ATCC 6633 and Bacillus megaterium CGMCC 1.1741. Their structures were identified on the basis of extensive spectroscopic methods and nine of them were found for the first time. Two main types of reactions, regio- and stereo-selective hydroxylation and glycosylation, especially in the unactivated C-H bonds including C-11, C-19 and C-27, were observed in the biotransformation process, which greatly expand the chemical diversities of GA derivatives. All compounds were tested for their inhibitory effects on nitric oxide (NO) generation in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. Among them, olean-12-ene-3β,7β,15α,19α,30-pentol (16) and olean-12-ene-3β,7β,15α,27,30-pentol (17) showed significant inhibitory effect with IC₅₀ values of 0.64 and 0.07 μM, respectively.     

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.     

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.     

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.     

Mechanism-based inhibitors of serine proteases with high selectivity through optimization of S′ subsite binding

A series of mechanism-based inhibitors designed to interact with the S′ subsites of serine proteases was synthesized and their inhibitory activity toward the closely-related serine proteases human neutrophil elastase (HNE) and proteinase 3 (PR 3) was investigated. The compounds were found to be time-dependent inhibitors of HNE and were devoid of any inhibitory activity toward PR 3. The results suggest that highly selective inhibitors of serine proteases whose primary substrate specificity and active sites are similar can be identified by exploiting differences in their S′ subsites. The best inhibitor (compound 16) had a k_inact/K_I value of 4580 M^?1 s^?1.     

Three new cyclopiane-type diterpenes from a deep-sea derived fungus Penicillium sp. YPGA11 and their effects against human esophageal carcinoma cells

Cyclopianes, featuring a highly rigid 6/5/5/5-fused tetracyclic framework, are structurally unique and biologically significant and belong to a rarely reported diterpenoid family. Chemical investigation of an EtOAc extract of a deep-sea-derived Penicillium sp. led to the isolation of three new cyclopiane diterpenes, namely, conidiogenols C–D (1–2) and conidiogenone L (3). The structures were determined by extensive analyses of the spectroscopic data in association with ECD calculations and chemical conversion for configurational assignments. Compound 1 represents the second example of cyclopianes bearing a hydroxyl group at C-13. Compound 2, the third example of conidiogenols, possesses a distinct α-oriented 1-hydroxy group relative to other analogues. The bioassay study demonstrated that compounds 2 and 4–6 exhibited moderate inhibitory effects against five esophageal cancer cell lines with IC₅₀ values ranging from 25 to 55 μM. The cytotoxicities of all compounds toward esophageal cancer cell lines were evaluated for the first time.     

Cytotoxic and non-cytotoxic cardiac glycosides isolated from the combined flowers,leaves, and twigs of Streblus asper

A new non-cytotoxic [(+)-17β-hydroxystrebloside (1)] and two known cytotoxic [(+)-3′-de-O-methylkamaloside (2) and (+)-strebloside (3)] cardiac glycosides were isolated and identified from the combined flowers, leaves, and twigs of Streblus asper collected in Vietnam, with the absolute configuration of 1 established from analysis of its ECD and NMR spectroscopic data and confirmed by computational ECD calculations. A new 14,21-epoxycardanolide (3a) was synthesized from 3 that was treated with base. A preliminary structure-activity relationship study indicated that the C-14 hydroxy group and the C-17 lactone unit and the established conformation are important for the mediation of the cytotoxicity of 3. Molecular docking profiles showed that the cytotoxic 3 and its non-cytotoxic analogue 1 bind differentially to Na⁺/K⁺-ATPase. Compound 3 docks deeply in the Na⁺/K⁺-ATPase pocket with a sole pose, and its C-10 formyl and C-5, C-14, and C-4′ hydroxy groups may form hydrogen bonds with the side-chains of Glu111, Glu117, Thr797, and Arg880 of Na⁺/K⁺-ATPase, respectively. However, 1 fits the cation binding sites with at least three different poses, which all depotentiate the binding between 1 and Na⁺/K⁺-ATPase. Thus, 3 was found to inhibit Na⁺/K⁺-ATPase, but 1 did not. In addition, the cytotoxic and Na⁺/K⁺-ATPase inhibitory 3 did not affect glucose uptake in human lung cancer cells, against which it showed potent activity, indicating that this cardiac glycoside mediates its cytotoxicity by targeting Na⁺/K⁺-ATPase but not by interacting with glucose transporters.     

Vieloplains A-G,seven new guaiane-type sesquiterpenoid dimers from Xylopia vielana

Seven new guaiane-type sesquiterpene dimers vieloplains A-G, connecting patterns through three different direct CC bonds compounds 1–5 (C-3 to C-3′, C-4 to C-1′), compound 6 (C-2 to C-3′, C-4 to C-2′) and compound 7 (C-2 to C-1′, C-4 to C-2′) were isolated from the roots of Xylopia vielana. Their absolute configurations were established by NOESY analysis, the Cu Kα X-ray crystallographic the experiment circular dichroism (ECD) and the calculated ECD. Among them, only compound 6 showed a considerable cytotoxicity against DU145 cells with IC₅₀ values of 9.5 μM. Flow cytometry analysis confirmed that 6 caused death of DU145 cells via apoptosis induction.