Novel cytotoxic amphiphilic nitro-compounds derived from a synthetic route for paraconic acids

Abstract

A series of precursors for bioactive paraconic acids (PA) were synthesized and their cytotoxicity assessed on human cells in vitro. Two amphiphilic nitro-containing precursors, Nitro-C15-EED and the butanolide Nitro-C12-GBL, were cytotoxic at the micromolar scale, with higher activity on tumor HeLa cells than on HEK-293T of non-tumor origin. The structure of these molecules is simple but different from reported bioactive nitro compounds. Nitro-C12-GBL was generally more cytotoxic, but after short-term (2 h) exposure both compounds reached maximum cytotoxicity. At 72 h post-treatments of HeLa cells the final dose-response for Nitro-C12-GBL (LC50 = 21.9 µmol L−1) was close to that for Nitro-C15-EED (LC50 = 25.3 µmol L−1), corresponding to LC50s ~ 3–3.6 times lower than those on HEK-293T. Short-term treatments with 50 µmol L−1 of these compounds promoted comparable outcomes, reducing tumor cells viability up to 27–36% of the controls and preserving ~70% of HEK-293T viability at 72 h post-treatments. Reduced cytotoxicity was observed in cultures continuously exposed to the compounds for longer periods (24–72 h), especially on tumor cells, underlining short-term treatments as alternatives to antiproliferative strategies. Due to their amphiphilic nature, these compounds show spontaneous surface activity and adsorption onto Langmuir monolayers of dipalmitoyl phosphatidyl choline (DPPC), especially Nitro-C12-GBL. The effects on DPPC monolayers are indicative of a possible physiological action that depends on the interaction with the cell membranes. Coarse-grained molecular dynamics indicate that individualized molecules of Nitro-C15-EED and the less toxic PA precursors are susceptible to trapping into phospholipid films. In contrast, Nitro-C12-GBL consistently forms large aggregates with outward polar domains, which could favor interaction with phospholipid polar heads of biological membranes.