Gossypol is a natural polyphenol presently considered as a promising biological phytochemical with a range of activities including anticancer. We examined volume regulation‐dependent effects of gossypol using erythrocytes and thymic lymphocytes. Gossypol effectively lysed human red blood cells (RBC) with a half‐maximal concentration of 67.4 ± 1.6 μmol/L and in a non‐colloid osmotic manner. Sublytic gossypol doses of 1–10 μmol/L significantly protected RBC from osmotic hemolysis, but potentiated their sensitivity to the colloid‐osmotic lysis induced by a pore‐former nystatin. When added to the thymocytes suspension, gossypol caused a strong depression of the ability of cells to restore their volume under hypoosmotic stress with a half‐maximal activity at 2.1 ± 0.3 μmol/L. Gossypol suppressed regulatory volume decrease under experimental conditions, when cationic permeability was controlled by gramicidin D, and volume recovery depended mainly on anionic conductance, suggesting that the polyphenol inhibits the swelling‐induced anion permeability. In direct patch‐clamp experiments, gossypol inhibited the volume‐sensitive outwardly rectifying (VSOR) chloride channel in thymocytes and in human HCT116 and HeLa cells, possibly by a mechanism when gossypol molecule with a radius close to the size of channel pore plugs into the narrowest portion of the native VSOR chloride channel. Micromolar gossypol suppressed proliferation of thymocytes, HCT116 and HeLa cells. VSOR blockage may represent new mechanism of anticancer activity of gossypol in addition to its action as a BH3‐mimetic.

Introduction: The first and most prevailing cells that glycyrrhizin (GL) and glycyrrhetinic acid (GA) encounter are red blood cells (RBCs). However, what follows this event is poorly understood. This study aims to evaluate the effect of GL and its derivatives on the integrity of human RBCs. Methods: The integrity of human RBC was assessed under normal isotonic conditions and following osmotic and nystatin-induced colloid-osmotic stress by measuring the amount of hemoglobin released. The pore size was determined by the osmotic protection method. Results: GL was found to be virtually non-hemolytic. However, removal of the carbohydrate moiety of GL imparted significant RBC lytic activity to the cis-(beta-) but not to the trans-(alpha-) isoform of GA. The hemisuccinate radical at position C3 (carbenoxolone) greatly diminished the hemolytic property of GA. The RBC lysis occurred by colloid-osmotic mechanism due to the formation of hydrophilic pores with the radius of ~2.3 nm. At the sublytic doses, the two stereo-isoforms displayed opposite effects on the osmo-resistivity of human RBC: osmoprotection for alpha-GA and osmotic sensibilization for beta-GA. Similar osmotic sensibilization was also observed for GL and carbenoxolone. The two stereo-isoforms exhibited different but not opposite weakening effects on the resistivity of the RBC to the colloid-osmotic stress induced by nystatin, a pore-former. The weakening effect was found intermediate for GL and absent for carbenoxolone. Conclusion: Upon intestinal digestion and absorption, depending on the structure and dosage, the GL hydrolysis products interact with RBC with both beneficial and detrimental consequences.

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