Novel Bidentate Amine Ligand and the Interplay between Pd(II) and Pt(II) Coordination and Biological Activity

Pt(II) and Pd(II) coordinating N-donor ligands have been extensively studied as anticancer agents after the success of cisplatin. In this work, a novel bidentate N-donor ligand, the N-[[4-(phenylmethoxy)phenyl]methyl]-2-pyridinemethanamine, was designed to explore the antiparasitic, antiviral and antitumor activity of its Pt(II) and Pd(II) complexes. Chemical and spectroscopic characterization confirm the formation of [MLCl2 ] complexes, where M=Pt(II) and Pd(II). Single crystal X-ray diffraction confirmed a square-planar geometry for the Pd(II) complex. Spectroscopic characterization of the Pt(II) complex suggests a similar structure. 1 H NMR, 195 Pt NMR and HR-ESI-MS(+) analysis of DMSO solution of complexes indicated that both compounds exchange the chloride trans to the pyridine for a solvent molecule with different reaction rates. The ligand and the two complexes were tested for in vitro antitumoral, antileishmanial, and antiviral activity. The Pt(II) complex resulted in a GI50 of 10.5 μM against the NCI/ADR-RES (multidrug-resistant ovarian carcinoma) cell line. The ligand and the Pd(II) complex showed good anti-SARS-CoV-2 activity with around 65 % reduction in viral replication at a concentration of 50 μM.

The role of spray-drying atmosphere on fridericia chica (bonpl.) L.G. Lohmann standardized extract production for wound healing activity

Fridericia chica (Bonpl.) L.G. Lohmann (synonym Arrabidaea chica Verlot) is widely used in Brazilian folk medicine. Considering overcoming pitfalls of scaling up production of plant extracts, herein the effects of N₂ atmosphere for extract spray-drying process is reported. Samples were monitored by in vitro antioxidant activity and microbiological evaluation. The drying atmosphere influenced 3-deoxyanthocyanines content when using air as atomizing gas, decreasing carajurin (37.5%) content with concomitant increase in luteolin yield (24.1%). Both drying processes preserved the pharmacological activity. In the cell migration test with HaCaT cells, the extract dried under air flow (5 μg/mL) promoted wound closure by 78% (12 hours) whereas the extract dried using N₂ flow promoted 49% (12 hours), with 98% closure (12 hours) for the positive control. The antimicrobial evaluation for Staphylococcus aureus did not differ within drying atmospheres, with MIC (minimum inhibitory concentration) at 0.39 mg/mL. Therefore, the drying process reported herein did not interfere with the biological activity's outcome.

Phytoprostane and phenolic compounds from Chromolaena palmaris

The chemical investigation of Chromolaena palmaris (Sch.Bip. ex Baker) R.M. King & H. Rob. expands the phytochemical composition knowledge of Chromolaena genus, since this is the first chemical investigation of this species. Twenty-five compounds were identified, including a phytoprostane, 17 flavonoids, 6 phenolic acids, and a caffeoyl-glucoside derivative obtained by classical chromatography and UHPLC-HRMS/MS analysis. Moreover, anti-Mycobacterium tuberculosis and antiproliferative activities of C. palmaris were evaluated. Dichloromethane fraction showed cytotoxicity towards human cancer cell lines, presenting TGI values on glioma (U251) of 27.8 μg mL^-1. Furthermore, compounds 1 and 2 exhibited antimicrobial activity against Mycobacterium tuberculosis with MIC of 62.5 and 15.6 μg mL^-1, respectively.

Novel anticancer PdII complexes: The effect of the conjugation of transferrin binding peptide and the nature of halogen coordinated on antitumor activity

A series of Pd^II complexes with bis-(2-pyridylmethyl)glycine as a ligand of formula [PdX(bis-(2-pyridylmethyl)glycine)] where X = Cl, Br, I were prepared and the effect of the halogen nature in the antitumor activity of eight tumorigenic and one non-tumorigenic cell line was evaluated. The chloride derivative was further functionalized with a transferrin receptor binding peptide, generating the first Pd^II based metallopeptide. Its antitumor activity was also evaluated. However, among all the complexes, the chloride and iodine parent compounds showed the lowest GI₅₀ values in the panel evaluated, and lowest GI₅₀ than cisplatin in several cell lines. In contrast, the bromine derivative showed higher values of GI₅₀ than chloride and iodine (around 30 - 50 μM). The same trend was observed for the bovine serum albumin binding constant with higher values for iodine, chlorine, and bromine in this order. In aqueous solution, the chloride is exchanged by water while the bromine and iodine are not. DNA was evaluated as a target and showed no significative interaction for all the compounds. The results suggest sulfur-rich proteins and not DNA as a target. This report represents the first Pd^II metallopeptide reported, its evaluation in solution and antitumor activity. This work opens the possibilities for further functionalization of Pd^II complexes and the importance of the halogen coordination in the design of novel metallodrugs.

Biological activities of eco-friendly synthesized Hantzsch adducts

Fourteen Hantzsch adducts with different substituents at the C-4 position were synthesized through multicomponent reactions by using citric or lactic acid as catalysts. To the best of our knowledge, this is the first report on the synthesis of such a class of compounds based on multicomponent reactions catalyzed by non-toxic organic acids. The potential to scavenge reactive nitrogen/oxygen species (RNS/ROS) and the ability to inhibit cancer cell growth were then investigated. Among the synthesized compounds, adduct 15 was the most promising free radical scavenger, while adduct 20 was shown to have a wider spectrum of action on the cancer cells studied. These results highlight Hantzsch adducts as lead compounds for obtaining new free radical scavengers and anticancer agents.

In vitro and in vivo antitumor activity of crude extracts obtained from Brazilian Chromobacterium sp isolates

Natural products produced by microorganisms have been an important source of new substances and lead compounds for the pharmaceutical industry. Chromobacterium violaceum is a Gram-negative β-proteobacterium, abundant in water and soil in tropical and subtropical regions and it produces violacein, a pigment that has shown great pharmaceutical potential. Crude extracts of five Brazilian isolates of Chromobacterium sp (0.25, 2.5, 25, and 250 µg/mL) were evaluated in an in vitro antitumor activity assay with nine human tumor cells. Secondary metabolic profiles were analyzed by liquid chromatography and electrospray ionization mass spectrometry resulting in the identification of violacein in all extracts, whereas FK228 was detected only in EtCE 308 and EtCE 592 extracts. AcCE and EtCE 310 extracts showed selectivity for NCI/ADR-RES cells in the in vitro assay and were evaluated in vivo in the solid Ehrlich tumor model, resulting in 50.3 and 54.6% growth inhibition, respectively. The crude extracts of Chromobacterium sp isolates showed potential and selective antitumor activities for certain human tumor cells, making them a potential source of lead compounds. Furthermore, the results suggest that other compounds, in addition to violacein, deoxyviolacein and FK228, may be involved in the antitumor effect observed.