PdCl2-catalyzed synthesis of a new class of isocoumarin derivatives containing aminosulfonyl / aminocarboxamide moiety: First identification of a isocoumarin based PDE4 inhibitor

While anti-inflammatory properties of isocoumarins are known their PDE4 inhibitory potential was not explored previously. In our effort the non-PDE4 inhibitor isocoumarins were transformed into the promising inhibitors via introducing an aminosulfonyl/aminocarboxamide moiety to the C-3 benzene ring attached to the isocoumarin framework. This new class of isocoumarins were synthesized via a PdCl2-catalyzed construction of the 4-allyl substituted 3-aryl isocoumarin ring starting from the appropriate 2-alkynyl benzamide derivative. Several compounds showed good inhibition of PDE4B in vitro and the SAR indicated superiority of aminosulfonamide moiety over aminocarboxamide in terms of PDE4B inhibition. Two compounds 3q and 3u with PDE4B IC50 = 0.43 ± 0.11 and 0.54 ± 0.19 μM and ≥ 2-fold selectivity over PDE4D emerged as initial hits. The participation of aminosulfonamide moiety in PDE4B inhibition and the reason for selectivity though moderate shown by 3q and 3u was revealed by the in silico docking studies. In view of potential usefulness of moderately selective PDE4B inhibitors the compound 3u (that showed PDE4 selectivity over other PDEs) was further evaluated in adjuvant induced arthritic rats. At an intraperitoneal dose of 30 mg/kg the compound showed a significant reduction in paw swelling (in a dose dependent manner), inflammation and pannus formation (in the knee joints) as well as pro-inflammatory gene expression/mRNA levels and increase in body weight. Moreover, besides its TNF-α inhibition and no significant toxicity in an MTT assay the compound did not show any adverse effects in a thorough toxicity studies e.g. teratogenicity, hepatotoxicity, cardiotoxicity and apoptosis in zebrafish. Thus, the isocoumarin 3u emerged as a new, safe and moderately selective PDE4B inhibitor could be useful for inflammatory diseases possibly including COVID-19.

Cytotoxic and apoptosis-inducing effects of novel 8-amido isocoumarin derivatives against breast cancer cells

Isocoumarin is a lactone, a type of natural organic compound that is used as synthetic intermediates of several natural products and pharmaceutical compounds explored for their potential therapeutic applications like antifungal, antimicrobial, anti-inflammatory, and anticancer activities. In our previous work, we were the first group to report the use of amide C-N bond of isatins as the oxidizing directing group for the synthesis of 8-amido isocoumarin derivatives. Whereas in our present work, we have screened the cytotoxic effects of novel 8-amido isocoumarin derivatives (S1-S10) in human breast cancer MCF-7 and MDA-MB-231 cells. Our novel results revealed that N-(3-(4-methoxyphenyl)-1-oxo-4-(4-propylphenyl)-1H-isochromen-8yl)acetamide (S1) and N-(4-(3,5-difluorophenyl)-1-oxo-3-(p-tolyl)-1H-isochromen-8-yl) acetamide (S2) are the two potent compounds among the rest synthesized isocoumarin derivatives that are cytotoxic against MCF-7 and MDA-MB-231 cells, whereas less toxic to the non-tumorigenic IOSE-364 cells. Flow cytometry studies have confirmed the induction of apoptotic effects of compounds by Annexin V/PI double staining. We also observed the cytotoxic effects of S1 and S2, as evaluated by DAPI-PI immunostaining and H&E staining. The morphological alterations consistent with apoptotic blebs were observed in both cancer cells treated with compounds assessed by scanning electron microscopy. Overall, this present study strongly demonstrates that 8-amido isocoumarin derivatives have potent cytotoxic and apoptotic effects in breast cancer cells.

Rosuvastatin based novel 3-substituted isocoumarins / 3-alkylidenephthalides: Ultrasound assisted synthesis and identification of new anticancer agents

A new class of 3-substituted isocoumarin/3-alkylidenephthalide based novel small molecules derived from rosuvastatin were designed and synthesized via the ultrasound assisted Cu-mediated coupling-cyclization in a single pot with remarkable regioselectivity. The phthalides were generally obtained at lower temperature whereas the use of elevated temperature afforded isocoumarins. Two compounds e.g. 3n and 4d showed promising cytotoxic effects when tested against HCT 116, HepG2 and PA-1 cell lines at 10 μM. Indeed, 4d was found to be a potent cytotoxic agent (IC₅₀ ∼ 0.76-4.51 μM). Both 3n and 4d were tested for their effects on PANC-1 cells. Considerable decrease in p-Akt substrates shown by 4d and 3n at 50 μM (western blot analysis) indicated their ability to inhibit p-Akt signal transduction pathway and arresting growth of PANC-1 cells in vitro. This was further supported by the cytotoxic effect of 4d on PANC-1 cells (MTT assay) that was better than rosuvastatin. While none of 3n and 4d showed any significant effect on non-cancerous HEK cell line (indicating their potential selectivity towards cancer cells) these compounds were further evaluated for their toxicities in Zebrafish embryo. The NOAEL (No Observed Adverse Effect Level) for teratogenicity, hepatotoxicity and cardiotoxicity was found to be 100 μM for both compound. Thus, 4d as a novel and potent but safer cytotoxic agent with potential to treat colorectal/ovarian and pancreatic cancer is of further medicinal interest.

Differential analysis of mycoalexins in confrontation zones of grapevine fungal pathogens by ultrahigh pressure liquid chromatography/time-of-flight mass spectrometry and capillary nuclear magnetic resonance

An original approach was developed for the chemical and biological investigation of zone lines formed by the confrontation of fungi growing in confined spaces. Two wood-decaying fungi involved in esca disease, Eutypa lata and Botryosphaeria obtusa, were grown in Petri dishes. Metabolic profiles of pure fungal strains and confrontation zones were differentially analyzed by ultrahigh pressure liquid chromatography coupled to time-of-flight mass spectrometry (UHPLC/TOFMS). Selected metabolites induced by the confrontation were isolated and characterized by capillary NMR (CapNMR) at the submilligram level. Fungitoxic and phytotoxic assays were applied to the crude extracts and isolated molecules. While the extracts of pure strains were inactive, the extract from confrontation zones exhibited significant activities. A very strongly induced compound, O-methylmellein, may explain these toxic properties. The developed approach demonstrates the use of fungal confrontations as an original source of bioactive molecules and gives new insights into the study of esca disease.