Tetrahydroquinoline and tetrahydroisoquinoline derivatives as potential selective PDE4B inhibitors

Targeting next-generation PDE4 inhibitors in search of potential management of rheumatoid arthritis and psoriasis

Immune-mediated inflammatory diseases (IMIDs) comprise a broad spectrum of conditions characterized by systemic inflammation affecting various organs and tissues, for which there is no known cure. The isoform-specific inhibition of phosphodiesterase-4B (PDE4B) over PDE4D constitutes an effective therapeutic strategy for the treatment of IMIDs that minimizes the adverse effects associated with non-selective PDE4 inhibitors. Thus, we report a new class of isoquinolone derivatives as next-generation PDE4 inhibitors for effective management of rheumatoid arthritis (RA) and psoriasis. Among the series, 8 compounds i.e. 1e, 1l, 1m, 1n, 1o, 2m, 2o and 3o showed promising PDE4B inhibition (>80 %) in vitro with IC50 ∼ 1.4-6.2 µM. The compound 1l was identified as an initial hit and was pursued for further studies. According to structure-activity relationship (SAR), an allyl group at C-4 position improved PDE4B inhibition. The correlation between in vitro activity data and binding affinities obtained via molecular docking suggested that the high-affinity binding to PDE4B is a prerequisite for the effective inhibition of PDE4B. Notably, the hit 1l showed selectivity towards PDE4B over PDE4D in vitro. Furthermore, 1l treatment (30 mg/kg) in the adjuvant-induced arthritis (AIA) rat model induced by complete Freund's adjuvant (CFA) demonstrated anti-arthritic potential via ameliorating paw swelling and body weight, narrowing joint space, reducing excessive immune cells infiltration and pannus formation in addition to reducing mRNA expression of pro-inflammatory cytokines such as TNF-α and IL-6 in synovial tissues of experimental rats. Additionally, 1l reduced the hyper-proliferative state and colony forming potential of IMQ-induced psoriatic keratinocytes. The treatment of these cells with 1l markedly reduced the protein levels of Ki67 and mRNA levels of pro-inflammatory cytokines e.g. IL-17A and TNF-α suggesting its potent anti-psoriatic potential. Furthermore, 1l did not show any significant adverse effects when evaluated in a systematic toxicity (e.g. teratogenicity, hepatotoxicity and cardiotoxicity) studies in zebrafish at the tested concentrations (1-100 µM) and the NOAEL (no-observed-adverse-effect level) was found to be 100 µM. Thus, with promising anti-inflammatory effects both in vitro and in vivo along with PDE4B selectivity with an acceptable safety margin, 1l emerged as a new and promising inhibitor for further studies.

Influence of heat processing on the anti-inflammatory activity of fresh Smilax glabra based on PDE4 inhibition

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Heat processing plays a key role in chemical profiles and health benefits of fresh SG.

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Fresh SG exhibits significant anti‐inflammatory effect based on PDE4 inhibition.

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The heat-labile quality and safety aspects of four astilbin isomers are compared.

Smilax glabra Roxb. (SG) is widely used as functional food with various beneficial effects. Fresh SG without processing has been eaten directly for anti-inflammation from ancient China, while the underlying mechanism remains underexplored. This study aims to investigate the anti-inflammatory activity of fresh SG by using metabolites profiles, affinity ultrafiltration mass spectrometry, PDE4 enzyme inhibition assay, and in silico analysis. Encouragingly, fresh SG showed promising anti-inflammatory effect with IC₅₀ value (0.009 μg/μL) on PDE4 was about 12 times higher than that of processed SG (0.110 μg/μL). Astilbin was identified as the main bioactive compound of fresh SG responsible for PDE4 inhibitory activity. We found that heat processing strongly affected astilbin isomerization, leading to significant changes in contents and PDE4 inhibitory activities of four astilbin isomers, resulting in decreased anti-inflammatory activity of fresh SG. This finding will provide theoretical basis for systematic research and food/nutraceutical applications of fresh Smilax glabra in the future.

Modular Photocatalytic Synthesis of α-Trialkyl-α-Tertiary Amines

Molecules displaying an α-trialkyl-α-tertiary amine motif provide access to an important and versatile area of biologically relevant chemical space but are challenging to access through existing synthetic methods. Here, we report an operationally straightforward, multicomponent protocol for the synthesis of a range of functionally and structurally diverse α-trialkyl-α-tertiary amines, which makes use of three readily available components: dialkyl ketones, benzylamines, and alkenes. The strategy relies on the of use visible-light-mediated photocatalysis with readily available Ir(III) complexes to bring about single-electron reduction of an all-alkyl ketimine species to an α-amino radical intermediate; the α-amino radical undergoes Giese-type addition with a variety of alkenes to forge the α-trialkyl-α-tertiary amine center. The mechanism of this process is believed to proceed through an overall redox neutral pathway that involves photocatalytic redox-relay of the imine, generated from the starting amine-ketone condensation, through to an imine-derived product. This is possible because the presence of a benzylic amine component in the intermediate scaffold drives a 1,5-hydrogen atom transfer step after the Giese addition to form a stable benzylic α-amino radical, which is able to close the photocatalytic cycle. These studies detail the evolution of the reaction platform, an extensive investigation of the substrate scope, and preliminary investigation of some of the mechanistic features of this distinct photocatalytic process. We believe this transformation will provide convenient access to previously unexplored α-trialkyl-α-tertiary amine scaffolds that should be of considerable interest to practitioners of synthetic and medicinal chemistry in academic and industrial institutions.

LFZ-4-46, a tetrahydroisoquinoline derivative, induces apoptosis and cell cycle arrest via induction of DNA damage and activation of MAPKs pathway in cancer cells

LFZ-4-46, that is [2-hydroxy-1-phenyl-1,5,6,10b-tetrahydropyrazolo(5,1-a) isoquinolin-3(2H)-yl](phenyl) methanone, a tetrahydroisoquinoline derivative with a pyrazolidine moiety, was synthetically prepared. The anti-cancer mechanism of the compound has not been clarified yet. In this study, the anticancer effects and potential mechanisms of LFZ-4-46 on human breast and prostate cancer cells were explored. (a) 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazoliumbromide assay was first performed to detect the effects of LFZ-4-46 on the viability of human cancer cells. (b) Comet assay was utilized to evaluate DNA damage. (c) Cell cycle, apoptosis and mitochondrial membrane potential were detected by flow cytometry. (d) The expression of relative proteins was detected by western blotting assay. LFZ-4-46 significantly inhibited the viability of cancer cells in a time- and dose-dependent manner and had no obviously inhibitory effect on the viability of mammary epithelial MCF-10A cells. Mechanistic studies demonstrated that LFZ-4-46-induced cell apoptosis and cycle arrest were mediated by DNA damage. It caused DNA damage through activating γ-H2AX and breaking DNA strands. Further studies showed that mitogen-activated protein kinasess pathway was involved in these activated several key molecular events. Finally, LFZ-4-46 showed a potent antitumor effect in vivo. These results suggest that LFZ-4-46 may be a potential lead compound for the treatment of breast and prostate cancer.

Exhaled volatilome analysis as a useful tool to discriminate asthma with other coexisting atopic diseases in women of childbearing age

The prevalence of asthma is considerably high among women of childbearing age. Most asthmatic women also often have other atopic disorders. Therefore, the differentiation between patients with atopic diseases without asthma and asthmatics with coexisting diseases is essential to avoid underdiagnosis of asthma and to design strategies to reduce symptom severity and improve quality of life of patients. Hence, we aimed for the first time to conduct an analysis of volatile organic compounds in exhaled breath of women of childbearing age as a new approach to discriminate between asthmatics with other coexisting atopic diseases and non-asthmatics (with or without atopic diseases), which could be a helpful tool for more accurate asthma detection and monitoring using a noninvasive technique in the near future. In this study, exhaled air samples of 336 women (training set (n = 211) and validation set (n = 125)) were collected and analyzed by thermal desorption coupled with gas chromatography-mass spectrometry. ASCA (ANOVA (analysis of variance) simultaneous component analysis) and LASSO + LS (least absolute shrinkage and selection operator + logistic regression) were employed for data analysis. Fifteen statistically significant models (p-value < 0.05 in permutation tests) that discriminated asthma with other coexisting atopic diseases in women of childbearing age were generated. Acetone, 2-ethyl-1-hexanol and a tetrahydroisoquinoline derivative were selected as discriminants of asthma with other coexisting atopic diseases. In addition, carbon disulfide, a tetrahydroisoquinoline derivative, 2-ethyl-1-hexanol and decane discriminated asthma disease among patients with other atopic disorders. Results of this study indicate that refined metabolomic analysis of exhaled breath allows asthma with other coexisting atopic diseases discrimination in women of reproductive age.

Substrate controlled, regioselective carbopalladation for the one-pot synthesis of C4-substituted tetrahydroisoquinoline analogues

6-Exo-trig cyclization reaction through regioselective carbopalladation was demonstrated with N-(2-halobenzyl)-N-allylamines to furnish the corresponding C4-substituted tetrahydroisoquinoline derivatives.

Synthesis, Purification, and Selective β2-AR Agonist and Bronchodilatory Effects of Catecholic Tetrahydroisoquinolines from Portulaca oleracea

A green, biomimetic, phosphate-mediated Pictet-Spengler reaction was used in the synthesis of three catecholic tetrahydroisoquinolines, 1, 2, and 12, present in the medicinal plant Portulaca oleracea, as well as their analogues 3-11, 13, and 14, with dopamine hydrochloride and aldehydes as the substrates. AB-8 macroporous resin column chromatography was applied for purification of the products from the one-step high-efficacy synthesis. It eliminated the difficulties in the isolation of catecholic tetrahydroisoquinolines from the aqueous reaction system and unreacted dopamine hydrochloride. Activity screening in CHO-K1/Gα15 cell models consistently expressing α_1B-, β₁-, or β₂-adrenergic receptors indicated that 12 and 2, compounds that are present in P. oleracea, possessed the most potent β₂-adrenergic receptor agonist activity and 2 was a selective β₂-adrenergic receptor agonist at the concentration of 100 μM. Both 12 and 2 exhibited dose-dependent bronchodilator effects on the histamine-induced contraction of isolated guinea-pig tracheal smooth muscle, with EC₅₀ values of 0.8 and 2.8 μM, respectively. These findings explain the scientific rationale of P. oleracea use as an antiasthmatic herb in folk medicine and provide the basis for the discovery of novel antiasthma drugs.

The crystal structure of 6-amino-2-methyl-8-(4-(methylthio)phenyl)-2,3,8,8a-tetrahydroisoquinoline-5,7,7(1H)-tricarbonitrile – ethanol (1/1), C20H19N5S

C20H19N5S.C2H6O, monoclinic, P21/c (no. 14), a = 12.1257(14) Å, b = 11.0862(14) Å, c = 16.0280(19) Å, β = 95.948(2)°, V = 2143.0(4) Å3, Z = 4, R gt(F) = 0.0486, wR ref(F 2) = 0.1487, T = 296(2) K.