Samdarshi Meena

Cu–Mn spinel oxide catalyzed synthesis of imidazo[1,2-a]pyridines through domino three-component coupling and 5-exo-dig cyclization in water

An efficient and eco-friendly synthesis of therapeutically important and structurally diverse imidazo[1,2-a]pyridines using recyclable bimetallic Cu–Mn spinel oxide catalyst in aqueous medium has been developed. The Cu–Mn catalyzed domino three-component coupling of 2-aminopyridines, aldehydes and alkynes followed by 5-exo-dig cycloisomerization produced desired imidazo[1,2-a]pyridines in good yields. The efficiency of this protocol could be attributed to the presence of these metals in multiple oxidation states (Cu2+, Mn2+, Mn3+ and Mn4+) in the bimetallic Cu–Mn catalyst. The advantages of this protocol over previous reports include the use of aqueous medium, recyclable catalyst, shorter reaction times and no requirement of any additive. This is the first method for synthesis of imidazo[1,2-a]pyridines which utilizes water as a reaction medium.

Secondary Metabolites from Endophytic Fungus Penicillium pinophilum Induce ROS-Mediated Apoptosis through Mitochondrial Pathway in Pancreatic Cancer Cells

The endophytic fungus strain MRCJ-326, isolated from Allium schoenoprasum, which is also known as Snow Mountain Garlic or Kashmiri garlic, was identified as Penicillium pinophilum on the basis of morphological characteristics and internal transcribed spacer region nucleotide sequence analysis. The endophytic fungus extract was subjected to 2D-SEPBOX bioactivity-guided fractionation and purification. The anthraquinone class of the bioactive secondary metabolites were isolated and characterized as oxyskyrin (1), skyrin (2), dicatenarin (3), and 1,6,8-trihydroxy-3-hydroxy methylanthraquinone (4) by spectral analysis. Dicatenarin and skyrin showed marked growth inhibition against the NCI60/ATCC panel of human cancer cell lines with least IC50 values of 12 µg/mL and 27 µg/mL, respectively, against the human pancreatic cancer (MIA PaCa-2) cell line. The phenolic hydroxyl group in anthraquinones plays a crucial role in the oxidative process and bioactivity. Mechanistically, these compounds, i.e., dicatenarin and skyrin, significantly induce apoptosis and transmit the apoptotic signal via intracellular reactive oxygen species generation, thereby inducing a change in the mitochondrial transmembrane potential and induction of the mitochondrial-mediated apoptotic pathway. Our data indicated that dicatenarin and skyrin induce reactive oxygen species-mediated mitochondrial permeability transition and resulted in an increased induction of caspase-3 apoptotic proteins in human pancreatic cancer (MIA PaCa-2) cells. Dicatenarin showed a more pronounced cytotoxic/proapopotic effect than skyrin due to the presence of an additional phenolic hydroxyl group at C-4, which increases oxidative reactive oxygen species generation. This is the first report from P. pinophilum secreating these cytotoxic/proapoptotic secondary metabolites.

Dysoxylum binectariferum bark as a new source of anticancer drug camptothecin: Bioactivity-guided isolation and LCMS-based quantification

Camptothecin (CPT, 1) is a potent anticancer natural product which led to the discovery of two clinically used anticancer drugs topotecan and irinotecan. These two drugs are semisynthetic analogs of CPT, and thus the commercial production of CPT as a raw material from various plant sources and tissue culture methods is highly demanding. In the present study, the Dysoxylum binectariferum bark, was identified as an alternative source of CPT, through bioassay-guided isolation. The barks showed presence of CPT (1) and its 9-methoxy analog 2, whereas CPT alkaloids were not present in seeds and leaves. This is the first report on isolation of CPT alkaloids from Meliaceae family. An efficient chromatography-free protocol for enrichment and isolation of CPT from D. binectariferum has been established, which was able to enrich CPT up to 21% in the crude extract. The LCMS (MRM)-based quantification method revealed the presence of 0.105% of CPT in dry barks of D. binectariferum. The discovery of CPT from D. binectariferum bark will certainly create a global interest in cultivation of this plant as a new crop for commercial production of CPT. Isolation of anticancer drug CPT from this plant, indicates that along with rohitukine, CPT and 9-methoxy CPT also contributes significantly to the cytotoxicity of D. binectariferum.

Pyrano-isochromanones as IL-6 inhibitors: synthesis, in vitro and in vivo antiarthritic activity.

Bergenin (1), a unique fused C-glycoside isolated from Bergenia species, possesses interesting anti-inflammatory and antipain activities. To study SAR of this scaffold, first-generation derivatives were synthesized and evaluated for inhibition of lymphocyte proliferation and production of pro-inflammatory cytokines. The C-7 substituted derivatives showed inhibition of IL-6 as well as TNF-α production. Bergenin and its most potent IL-6 inhibitor derivatives 4e and 4f were then investigated in a panel of in vitro and in vivo inflammation/arthritis models. These compounds significantly decreased the expression of NF-kB and IKK-β in THP-1 cells. In in vivo study in BALB/c mice, a dose-dependent inhibition of SRBC-induced cytokines, reduction in humoral/cell-mediated immunity, and antibody titer was observed. The CIA study in DBA/1J mice indicated that compounds led to reduction in swelling of paws, cytokine levels, and anticollagen IgG1/IgG2a levels. The significant in vivo immunosuppressive efficacy of pyrano-isochromanones demonstrates the promise of this scaffold for development of next-generation antiarthritic drugs.

QSAR and pharmacophore modeling of N-acetyl-2-aminobenzothiazole class of phosphoinositide-3-kinase-α inhibitors

The mTOR-mediated PI3K/AKT/mTOR signal transduction pathway plays a key role in a broad spectrum of cancers. In the present article, QSAR and pharmacophore studies were carried out using a series of 61 benzothiazole class of PI3Kα inhibitors to characterize molecular features and structural requirements crucial for biological interaction. QSAR study performed using TSAR 3.3 by multiple regression analysis and partial least square methods identified inertia moment-1-size, kier chiv5 (path) index, and number of H-bond donors as important descriptors responsible for PI3Kα inhibitory activity. Further analysis of pharmacophore model by means of Phase module of Schrodinger revealed that two hydrogen-bond acceptors, one hydrogen-bond donors, and two hydrophobic aromatic rings as crucial molecular features that predict binding affinity for high-affinity ligands to the PI3Kα enzyme. These observations provide important insights to the key structural requirements of these molecules for potent PI3Kα inhibition. Excellent statistical results of developed models strongly suggest that these models are reasonable for the prediction of the activity of new inhibitors and in future drug design.

KF/alumina catalyzed regioselective benzylation and benzoylation using solvent-free grind-stone chemistry

Potassium fluoride-impregnated on alumina catalyzes solvent-free regioselective O-benzylation, benzoylation and cinnamylation of phenols. Reaction proceeds simply by triturating together equivalent amounts of phenol and corresponding halide in the presence of 5 mol% of KF/alumina for 5–20 min with a mortar and pestle, without need for any additive such as phase-transfer catalyst or solvent. Key features of the protocol include its efficiency also for solid–solid precursors and regioselectivity for phenolic hydroxyls versus alcoholic hydroxyls. Utility of the protocol for N- and S-benzylation has also been explored. Products were obtained in excellent yields and the catalyst can be easily recycled several times without significant loss of activity.