Design, synthesis and inhibitory effect of pentapeptidyl chloromethyl ketones on proteinase K

The synthesis and proteolytic inhibitor function of new modified pentapeptide MeOSuc-AAAPF-CH₂Cl 6 is described. The efficacy of 6 in inhibiting the proteolytic activity of proteinase K at a concentration of 0.10 mM allows a signal to be obtained for an exogenous target (‘Xeno RNA’) at 29 PCR cycles (i.e., Ct = 29), whereas the control MeOSuc-AAAPV-CH₂Cl 1 requires a 7.5-fold higher concentration (0.75 mM) to produce the same Ct.     

Synthesis and biological evaluation of heterocyclic ring-substituted maslinic acid derivatives as novel inhibitors of protein tyrosine phosphatase 1B

A series of maslinic acid derivatives have been synthesized by introducing various fused heterocyclic rings at C-2 and C-3 positions. Their inhibitory effects on PTP1B, TCPTP and related PTPs are evaluated. Most of the compounds exhibited a dramatic increase in inhibitory potency and selectivity, the two most potent PTP1B inhibitors 20 (IC₅₀ = 0.61 μM) and 29 (IC₅₀ = 0.64 μM) showed about 10-fold more potent than lead compound maslinic acid. More importantly, 29 possesses the best selectivity of 6.9-fold for PTP1B over TCPTP.     

Effects of triterpene derivatives from Maytenus rigida on VEGF-induced Kaposi's sarcoma cell proliferation

Betulinic acid (BA) is a naturally occurring lupane-type triterpene which exhibits a variety of biological activities including potent cytotoxic properties. On the basis of the structural similarity to BA, two lupane derivatives namely lup-20(29)-ene-3β,30-diol (1) and lup-20(29)-ene-3β,28-diol (2), along with two friedelane derivatives, namely friedelan-3-one (3) and friedelan-3β-ol (4), isolated from the Brazilian plant Maytenus rigida, have been evaluated for their anti-proliferative effect. Similarly to BA, compounds 1 and 3 at 1 μM concentration significantly inhibited the VEGF-induced Kaposi's sarcoma (KS) cell proliferation by 50%. In contrast, this effect was not found in control endothelial cells (EC).Moreover, compounds 1 and 3 showed a dose-dependent effect on the apoptotic cell death, as detected by FACS analysis and caspase-3 assay. Specifically, at 10 μM concentration, apoptosis was significantly induced (from 45% to 55% of hypodiploid cells vs control cells) and showed the same potency order observed for the anti-proliferative effect at 1 μM, i.e., compound 3 > BA > compound 1.Taking into account the interest given rise by BA as anticancer agent, the comparable anti-proliferative activity shown by compounds 1 and 3 and BA, can give an impulse to further investigate lupane and friedelane derivatives as cytotoxic agents.     

Isolation,structure, and bioactivities of abiesadines A–Y, 25 new diterpenes from Abies georgei Orr

Twenty-five new (abiesadines A–Y, 1–25) and 29 known (26–54) diterpenes were isolated from the aerial parts of Abies georgei. Abiesadine A (1) is a novel 8,14-seco-abietane, while abiesadine B (2) is a novel 9,10-seco-abietane. The structures of the new compounds were established on the basis of spectroscopic data analysis. Manool (52) showed the strongest effect against LPS-induced NO production in RAW264.7 macrophages with the IC₅₀ value of 11.0 μg/mL. In another anti-inflammatory assay against TNFα-triggered NF-κB activity, (12R,13R)-8,12-epoxy-14-labden-13-ol (54) exhibited the strongest effect (IC₅₀ = 8.7 μg/mL). For antitumor assays, pomiferin A (26) and 8,11,13-abietatriene-7α,18-diol (29) both showed the most significant activity against LOVO cells (IC₅₀ = 9.2 μg/mL). While 7-oxocallitrisic acid (46) exhibited significant cytotoxicity against QGY-7703 tumor cells (IC₅₀ = 10.2 μg/mL).     

Bioactivity-guided isolation of cytotoxic constituents from stem–bark of Premna tomentosa

A bioassay-guided fractionation and chemical investigation of the stem bark of Premna tomentosa resulted in the isolation and characterization of four new icetexane diterpenes (1–4), along with the known compounds coniferaldehyde (5), syringaldehyde (6), lupeol (7), betulin (8), and 2-(4-methoxyphenyl)-2-butanone (9). Their structures were established on the basis of extensive spectroscopic (IR, MS, 2D NMR) data analysis and by comparison with the spectroscopic data reported in the literature. The new compounds exhibited diverse functionalities on a common icetexane diterpene skeleton. In addition, cytotoxic activities of the icetexanes (1–3) were evaluated by determining their inhibitory effects on the human cancer cell lines (MCF-7, HT-29, Hep-G2, A-431, and A-549). Compounds 1 and 3 showed selective inhibitory activity against MCF-7 (15.96 μg/mL and 15.84 μg/mL) and HT-29 cell lines (16.21 μg/mL and 14.57 μg/mL), respectively.     

Identification and synthesis of 2,7-diamino-thiazolo[5,4-d]pyrimidine derivatives as TRPV1 antagonists

We have identified and synthesized a series of 2,7-diamino-thiazolo[5,4-d]pyrimidines as TRPV1 antagonists. An exploration of the structure–activity relationships at the 2-, 5-, and 7-positions of the thiazolo[5,4-d]pyrimidine led to the identification of several potent TRPV1 antagonists, including 3, 29, 51, and 57. Compound 3 was orally bioavailable and afforded a significant reversal of carrageenan-induced thermal hyperalgesia with an ED₅₀ = 0.5 mg/kg in rats.     

Dammarane-type saponins from Gynostemma pentaphyllum

Dammarane-type saponins, gypenosides VN1–VN7 (1–7), were isolated from the total saponin extract of Gynostemma pentaphyllum aerial parts, with their structures elucidated on the basis of spectroscopic and chemical methods. These compounds showed moderate cytotoxic activity against four human cancer cell lines, A549 (lung), HT-29 (colon), MCF-7 (breast), and SK-OV-3 (ovary), with IC₅₀ values ranging from 19.6 ± 1.1 to 43.1 ± 1.0 μM. Regarding the HL-60 (acute promyelocytic leukemia) cell line, compounds 1, 5, and 6 showed weakly active with IC₅₀ values of 62.8 ± 1.9, 72.6 ± 3.6, and 82.4 ± 3.2 nM, respectively, while 2, 3, 4, and 7 were less active with IC₅₀ values >100 μM.     

Synthesis of a second generation chroman/catechol hybrids and evaluation of their activity in protecting neuronal cells from oxidative stress-induced cell death

A new generation of chroman/catechol hybrids bearing heterocyclic five-membered rings, such as 1,2,4-oxadiazole 1,3,4-oxadiazole, 1,2,3-triazole, tetrazole and isoxazole, were designed and synthesized. The activity of the new derivatives against oxidative stress induced neuronal damage, was evaluated using glutamate-challenged hippocampal HT22 cells.Compound 3 in which a 3,4-dimethoxyphenyl moiety, is directly attached to the 1,2,4-oxadiazole ring was the most active among the 2-substituted chroman analogues, with EC₅₀ = 254 ± 65 nM. Concerning the 5-subtituted chroman analogues, isoxazole derivative 29 exhibited the strongest activity (EC₅₀ = 245 ± 38 nM). However, 29 was cytotoxic at concentrations higher than 1 μM, while the triazole analogue 24 (EC₅₀ = 801 ± 229 nM), was non-toxic at all concentrations tested.     

Synthesis and preclinical characterization of 1-(6′-deoxy-6′-[18F]fluoro-β-d-allofuranosyl)-2-nitroimidazole (β-6′-[18F]FAZAL) as a positron emission tomography radiotracer to assess tumor hypoxia

Positron emission tomography (PET) using fluorine-18 (¹⁸F)-labeled 2-nitroimidazole radiotracers has proven useful for assessment of tumor oxygenation. However, the passive diffusion-driven cellular uptake of currently available radiotracers results in slow kinetics and low tumor-to-background ratios. With the aim to develop a compound that is actively transported into cells, 1-(6′-deoxy-6′-[¹⁸F]fluoro-β-d-allofuranosyl)-2-nitroimidazole (β-[¹⁸F]1), a putative nucleoside transporter substrate, was synthetized by nucleophilic [¹⁸F]fluoride substitution of an acetyl protected labeling precursor with a tosylate leaving group (β-6) in a final radiochemical yield of 12 ± 8% (n = 10, based on [¹⁸F]fluoride starting activity) in a total synthesis time of 60 min with a specific activity at end of synthesis of 218 ± 58 GBq/μmol (n = 10). Both radiolabeling precursor β-6 and unlabeled reference compound β-1 were prepared in multistep syntheses starting from 1,2:5,6-di-O-isopropylidene-α-d-allofuranose. In vitro experiments demonstrated an interaction of β-1 with SLC29A1 and SLC28A1/2/3 nucleoside transporter as well as hypoxia specific retention of β-[¹⁸F]1 in tumor cell lines. In biodistribution studies in healthy mice β-[¹⁸F]1 showed homogenous tissue distribution and excellent metabolic stability, which was unaffected by tissue oxygenation. PET studies in tumor bearing mice showed tumor-to-muscle ratios of 2.13 ± 0.22 (n = 4) at 2 h after administration of β-[¹⁸F]1. In ex vivo autoradiography experiments β-[¹⁸F]1 distribution closely matched staining with the hypoxia marker pimonidazole. In conclusion, β-[¹⁸F]1 shows potential as PET hypoxia radiotracer which merits further investigation.     

Antiplatelet aggregation triterpene saponins from the leaves of Ilex kudingcha

Two new ursane-type triterpene saponins, 3-O-β-d-glucopyranosyl(1 → 3)-[α-l-rhamnopyranosyl(1 → 2)]-α-l-arabinopyranosylurs-12,19(29)-dien-28-oic acid 28-O-α-l-rhamnopyranosyl(1 → 2)-β-d-glucopyranosyl ester (1) and 3-O-β-d-glucopyranosyl(1 → 3)-[α-l-rhamnopyranosyl(1 → 2)]-α-l-arabinopyranosyl-19α,20α-dihydroxyurs-12-en-28-oic acid 28-O-α-l-rhamnopyranosyl(1 → 2)-β-d-glucopyranosyl ester (2), along with thirteen known triterpene saponins were isolated from the n-BuOH part of the MeOH extraction of the leaves of Ilex kudingcha C.J. Tseng (also called “Ku-Ding-Cha”). The structures of new compounds were elucidated on the basis of detailed spectroscopic analysis, including HR-ESI-TOF-MS, 1D and 2D-NMR experiments, and by acid hydrolysis. All the compounds were screened for antiplatelet aggregation activity in vitro, and compounds 1, 2, 3, 7, 12 and 15 showed significant inhibition of platelet aggregation induced by ADP (5 μM) with IC₅₀ values of 14.7 ± 3.7, 11.3 ± 2.5, 17.4 ± 4.6, 20.5 ± 3.1, 8.1 ± 1.5 and 18.9 ± 4.2 μM, respectively.     

Sulfur incorporation generally improves Ricin inhibition in pterin-appended glycine-phenylalanine dipeptide mimics

Several 7-aminoamido-pterins were synthesized to evaluate the electronic and biochemical subtleties observed in the ‘linker space’ when N-{N-(pterin-7-yl)carbonylglycyl}-l-phenylalanine 1 was bound to the active site of RTA. The gylcine–phenylalanine dipeptide analogs included both amides and thioamides. Decarboxy gly-phe analog 2 showed a 6.4-fold decrease in potency (IC₅₀ = 128 μM), yet the analogous thioamide 7 recovered the lost activity and performed similarly to the parent inhibitor (IC₅₀ = 29 μM). Thiourea 12 exhibited an IC₅₀ nearly six times lower than the oxo analog 13. All inhibitors showed the pterin head-group firmly bound in their X-ray structures yet the pendants were not fully resolved suggesting that all pendants are not firmly bound in the RTA linker space. Calculated log P values do not correlate to the increase in bioactivity suggesting other factors dominate.     

Natural neuro-inflammatory inhibitors from Caragana turfanensis

Because of the critical role of over-activated microglia in the progress of neurodegenerative diseases, it has been selected as a potential therapeutic target for drug discovery. In order to find natural neuroinflammatory inhibitors, we carried out a bioactivity-oriented phytochemical research of Caragana turfanensis Kom. (Krassn.), which is a folk medicine widely distributed in Xinjiang. As a result, a new coumarin lactone caraganolide A (1) and 35 known components were characterized from the effective extract of C. turfanensis. Furthermore, their anti-neuroinflammatory effects were evaluated in LPS-induced BV2 microglial cells using Griess assay to determine the release of nitric oxide (NO). Compounds 1, 2, 4–6, 9, 13–15, 20, 29 and 30 exhibited significant inhibitory activities and no obvious cytotoxicities were observed at their effective concentrations. It is noteworthy, the new compound caraganolide A (1) (IC₅₀ 1.01 ± 1.57 µM) and 3′,7,8-trihydroxy-4′-methoxyisoflavone (5) (IC₅₀6.87 ± 2.23 µM) exhibited more excellent action than that of positive control minocycline (IC₅₀ 9.07 ± 0.86 μM).     

The novel benzopyran class of selective cyclooxygenase-2 inhibitors. Part 2: The second clinical candidate having a shorter and favorable human half-life

In this Letter, we provide the structure–activity relationships, optimization of design, testing criteria, and human half-life data for a series of selective COX-2 inhibitors. During the course of our structure-based drug design efforts, we discovered two distinct binding modes within the COX-2 active site for differently substituted members of this class. The challenge of a undesirably long human half-life for the first clinical candidate 1 t_1/2 = 360 h was addressed by multiple strategies, leading to the discovery of 29b-(S) (SC-75416) with t_1/2 = 34 h.     

New bioactive dihydrofuranocoumarins from the roots of the Tunisian Ferula lutea (Poir.) Maire

A phytochemical investigation of the roots of Ferula lutea (Poir.) Maire led to the isolation of new dihydrofuranocoumarins as two inseparable isomers, (?)-5-hydroxyprantschimgin 1 and (?)-5-hydroxydeltoin 2, together with eight known compounds, (?)-prantschimgin 3, (?)-deltoin 4, psoralen 5, xanthotoxin 6, umbelliferone 7, caffeic acid 8, β-sitosterol 9 and stigmasterol 10. Their structures were elucidated on the basis of extensive spectroscopic methods, including 1D and 2D NMR experiments and mass spectroscopy analysis, as well as by comparison with literature data. The anti-acetylcholinesterase and cytotoxic effects of the isolates and antioxidant activities of the mixture (1+2) were also evaluated in this work. Results showed that the mixture (1+2) has the most cytotoxic activity with IC₅₀ values 0.29 ± 0.05 and 1.61 ± 0.57 μM against the cell lines HT-29 and HCT 116, respectively. The greatest acetylcholinesterase inhibitory activity (IC₅₀ = 0.76 ± 0.03) was exhibited by the xanthotoxin 6. In addition, the mixture (1+2) was investigated for its antioxidant activity and showed IC₅₀ values 18.56, 13.06, 7.59, and 4.81 μM towards DPPH free radical scavenging, ABTS radical monocation, singlet oxygen and hydrogen peroxide, respectively.     

Antioxidant prenylated phenols of Artocarpus plants attenuate ultraviolet radiation-induced damage on human keratinocytes and fibroblasts

Two novel prenylated phenols, cyclocomunoindenol (1) and cyclocomunohexanol (2) were isolated from the cortex of roots of Artocarpus communis. Their structures were determined by spectroscopic methods. Compounds 2 and 6 revealed significant DPPH-scavenging activity with an IC₅₀ values of 435.48 ± 0.93 and 53.55 ± 8.73 μM, respectively. Compounds 1, 2, and 6 displayed significant ABTS⁺ scavenging activity with an IC₅₀ values of 164.26 ± 2.44, 227.01 ± 3.64, and 44.09 ± 0.88 μM, respectively. Compound 6 exhibited an inhibitory effect on XO activity with an IC₅₀ value of 10.91 ± 1.77 μM and the relative oxygen radical absorbance capacity (ORAC) values of 1–6, using ORAC-pyrogallol red (PGR) assay, were determined to be 0.28 ± 0.06, 0.31 ± 0.02, 0.55 ± 0.25, 0.84 ± 0.36, 0.35 ± 0.15, and 0.70 ± 0.09, respectively. Antioxidants 5 and 6 significantly attenuate UVA radiation-induced damage on human HaCaT keratinocytes and Hs68 fibroblasts. These finding showed that 1–6 may be used as antioxidants and 5 and 6 may protect skin against the adverse effects of UV radiation.     

Evaluation of N-substitution in 6,7-benzomorphan compounds

6,7-Benzomorphan derivatives, exhibiting different μ, δ, and κ receptor selectivity profiles depending on the N-substituent, represent a useful skeleton for the synthesis of new and better analgesic agents. In this work, an aromatic ring and/or alkyl residues have been used with an N-propanamide or N-acetamide spacer for the synthesis of a new series of 5,9-dimethyl-2′-hydroxy-6,7-benzomorphan derivatives (12–22). Data obtained by competition binding assays showed that the μ opioid receptor seems to prefer an interaction with the 6,7-benzomorphan ligands having an N-substituent with a propanamide spacer and less hindered amide. Highly stringent features are required for δ receptor interaction, while an N-acetamide spacer and/or bulkier amide could preferentially lead to κ receptor selectivity. In the propanamide series, compound 12 (named LP1) displayed high μ affinity (K_i = 0.83 nM), good δ affinity (K_i = 29 nM) and low affinity for the κ receptor (K_i = 110 nM), with a selectivity ratio δ/μ and κ/μ of 35.1 and 132.5, respectively. Further, in the adenylyl cyclase assay, LP1 displayed a μ/δ agonist profile, with IC₅₀ values of 4.8 and 12 nM at the μ and δ receptors, respectively. The antinociceptive potency of LP1 in the tail-flick test after sc administration in rat was comparable with the potency of morphine (ED₅₀ = 2.03 and 2.7 mg/kg, respectively), and was totally reversed by naloxone. LP1, possessing a μ/δ agonist profile, could represent a lead in further developing benzomorphan-based ligands with potent in vivo analgesic activity and a reduced tendency to induce side effects.     

Triterpenoid saponins from the aerial parts of Trifolium argutum Sol. and their phytotoxic evaluation

Four triterpenoid saponins (1–4) were isolated from the aerial parts of Trifolium argutum Sol. (sharp-tooth clover) and their structures were elucidated by comprehensive spectroscopic analysis, including 1D and 2D NMR techniques, mass spectrometry and chemical methods. Two of them are new compounds, characterized as 3-O-[α-l-rhamnopyranosyl-(1→2)-β-d-galactopyranosyl-(1→2)-β-d-glucuronopyranosyl]-3β,24-dihydroxyolean-12-ene-22-oxo-29-oic acid (1) and 3-O-[β-d-galactopyranosyl-(1→2)-β-d-glucuronopyranosyl]-3β,24-dihydroxyolean-12-ene-22-oxo-29-oic acid (2). The occurrence of 3β,24-dihydroxyolean-12-ene-22-oxo-29-oic acid (melilotigenin) in its natural form is reported for the first time as a triterpenoid aglycone within Trifolium species. The phytotoxicity of compounds was evaluated on four STS at concentration 1 μM to 333 μM. Compound 1 was the most active, showing more than 60% inhibition on the root growth of L. sativa at the higher dose, with IC₅₀ (254.1 μM) lower than that of Logran^® (492.6 μM), a commercial herbicide used as positive control. The structure–activity relationships indicated that both aglycones and glycosidic parts may influence the phytotoxicity of saponins.     

Synthesis and in vitro evaluation of anti-inflammatory activity of ester and amine derivatives of indoline in RAW 264.7 and peritoneal macrophages

A prolonged increase in pro-inflammatory cytokines, TNF-α and IL-6 occurs in inflammatory diseases. Although existing therapies like steroids and TNF-α antagonists are effective they may cause serious adverse effects. We describe the preparation and evaluation for anti-inflammatory activity of 11 novel derivatives of indoline carbamates with a propionic ester, 2-aminoethyl, 3-aminopropyl 2-(dimethylamino)ethyl or 3-(dimethylamino)propyl group in positions 3 or 1. Compounds 25, 26 and 29 were previously shown to inhibit acetylcholinesterase with IC_50s ranging from 0.4 to 55 μM and to prevent cytotoxicity induced by reactive oxygen species in a concentration range of 100 pM–1 μM. Compounds 25, 26, 29, 9, 10, 17 and 18, reduced NO, TNF-α and IL-6 at concentrations of 1–10 pM in LPS-activated RAW-264.7 and mouse peritoneal macrophages. The reduction in cytokines by compound 25 was associated with an increase in IκBα degradation and a decrease in the phosphorylation of p38 but not that of ERK. Conclusion: Indoline derivatives substituted at position 3 with chains carrying ester or amino groups may have potential for the treatment of chronic inflammatory and neurodegenerative diseases.     

Schiff bases of 3-formylchromone as thymidine phosphorylase inhibitors

3-Formylchromone (1), 3-methyl-7-hydroxychromone (2) and Schiff bases of 3-formylchromone 3–19 have been synthesized and their anti-thymidine phosphorylase inhibitory activity was evaluated. Compounds 1–19 showed a varying degree of thymidine phosphorylase inhibition with IC₅₀ values 19.77 ± 3.25 to 480.21 ± 2.34 μM. Their activity was compared with the standard 7-deazaxanthine (IC₅₀ = 39.28 ± 0.76 μM). Compound 12 showed an excellent thymidine phosphorylase inhibitory activity with an IC₅₀ value of 19.77 ± 3.25 μM, better than the standard. Compound 4 also showed an excellent inhibitory activity (IC₅₀ = 40.29 ± 4.56 μM). The parent 3-formylchromone (1) and 3-methyl-7-hydroxychromone (2) were found to be inactive. The structures of the compounds were elucidated by using spectroscopic techniques, including ¹H NMR, EI MS, IR, UV and elemental analysis.     

Synthesis and anticancer activity of focused compound libraries from the natural product lead,oroidin

Oroidin (1), (E)-N-(3-(2-amino-1H-imidazol-4-yl)allyl)-4,5-dibromo-1H-pyrrole-2-carboxamide, is a pyrrole alkaloid isolated from the marine sponge Agelas oroides. Routine screening in a panel of twelve cancer cell lines revealed 1 to be poorly cytotoxic with the 50% growth inhibition concentration (GI₅₀) of 42 μM in MCF-7 (breast) cells and 24 μM in A2780 (ovarian) cells and >50 μM in all other cell lines tested. The development of eight focused libraries comprising thirty compounds total identified N-(biphenyl-4-ylmethyl)-1H-pyrrole-2-carboxamide (4l), N-benzyl-4,5-dibromo-1H-pyrrole-2-carboxamide (5a) and N-(biphenyl-4-ylmethyl)-4,5-dibromo-1H-pyrrole-2-carboxamide (5l) as potent inhibitors of cell growth in our panel of cell lines. Of these compounds GI₅₀ values of <5 μM were observed with 4l against HT29 (colon) and SW480 (colon); 5a against HT29; and 5l against HT29, SW480, MCF-7, A431 (skin), Du145 (prostate), BE2-C (neuroblastoma) and MIA (pancreas) cell lines. As a cancer class, colon cancer appears to be more sensitive to the oroidin series of compounds, with analogue 5l being the most active.