Investigation of the anticancer mechanism of monensin via apoptosis-related factors in SH-SY5Y neuroblastoma cells

Comparative Evaluation of Cytotoxic and Apoptotic Effects of Natural Compounds in SH-SY5Y Neuroblastoma Cells in Relation to Their Physicochemical Properties

The cytotoxic and apoptotic properties of four bioactive natural compounds, the prenylated α-pyronephloroglucinol heterodimer arzanol (ARZ), the methoxylated flavones eupatilin (EUP) and xanthomicrol (XAN), and the sesquiterpene zerumbone (ZER), were compared in SH-SY5Y human neuroblastoma cells to assess their potential as neuroblastoma-specific therapeutics. EUP, XAN, and ZER (2.5-100 μM) exerted marked significant cytotoxicity (MTT assay) and morphological changes after 24 h of incubation, following the order XAN > ZER > EUP > ARZ (no toxic effect). The propidium iodide fluorescence assay (PI, red fluorescence) and NucView® 488 assay (NV, green fluorescence) evidenced a significant increase in the apoptotic cell number, vs. controls, in SH-SY5Y cells pre-incubated for 2 h with the compounds, in the following order of apoptotic potency: XAN > EUP > ZER > ARZ. The PubChem database and freely accessible web tools SwissADME, pkCSM-pharmacokinetics, and SwissTargetPrediction were used to assess the physicochemical/pharmacokinetic properties and potential protein targets of the compounds. At 50 μM, a positive correlation (r = 0.917) between values of % viability reduction and % human intestinal absorption (bioavailability) was observed, indicating a marked contribution of compound membrane permeability to cytotoxicity in SH-SY5Y cells. The capacity of compounds to induce apoptosis emerged as inversely correlated to the computed lipophilicity (r = -0.885).

Metal Ion-Induced Large Fragment Deactivation: A Different Strategy for Site-Selectivity in a Complex Molecule

Complex natural product functionalizations generally involve the use of highly engineered reagents, catalysts, or enzymes to react exclusively at a desired site through lowering of a select transition state energy. In this communication, we report a new, complementary strategy in which all transition states representing undesirable sites in a complex ionophore substrate are simultaneously energetically increased through the chelation of a metal ion to the large fragment we wish to neutralize. In the case of an electrophilic, radical based fluorination reaction, charge repulsion (electric field effects), induced steric effects, and electron withdrawal provide the necessary deactivation and proof of principle to afford a highly desirable natural product derivative. We envisage that many other electrophilic or charge based synthetic methods may be amenable to this approach as well.