Benzothiazepane‐Based Curcumin Analogs Show Selective Effects on Respiration, Permeability, and Growth of Gut‐Liver (Co‐Culture) Cell Models

ABSTRACT

Curcumin, a natural polyphenol with anti‐cancer potential, faces limitations due to metabolic instability, and non‐specific toxicity. This study focused on four curcumin analogs (FM038, FM044, FM045, FM050) featuring oxobutenylidene‐substituted benzothiazepane cores bearing pyridinyl or furan substituents. We systematically evaluated their selective toxic effect on human colon (Caco‐2) and liver (HepG2) cells. This study reveals that structural modifications critically govern the selective cytotoxicity of curcumin analogs towards proliferating Caco‐2 and HepG2 cells. Treatment with analogs featuring pyridin‐2‐yl substituents (FM045/FM050) resulted in a slightly reduced potency towards Caco‐2 cells compared to curcumin, whereas FM044 (furan‐2‐yl) was non‐toxic and FM038 (pyridin‐3‐yl, methylated core) maintained similar activity. In contrast, direct exposure to proliferating HepG2 cells resulted in less cytotoxicity compared to the Caco‐2 cell line, which points to a cell‐specific mode‐of‐action in growing cells. When combined in a co‐culture, metabolites generated and/or transported by differentiated Caco‐2 cells significantly decreased HepG2 viability at an apical concentration of 15 μM. Efflux analysis of respiration and acidification showed that FM050 induced the strongest mitochondrial dysfunction in Caco‐2 cells, directly driving cytotoxicity, whereas HepG2 toxicity correlated with intrinsic detoxification capacity rather than mitochondrial disruption. A metabolic shift towards glycolysis was observed in both cell lines, indicating energy pathway modulation to a more dysfunctional phenotype. These findings highlight the dual role of structural optimization (e.g., methylation, heterocyclic substituents) for (cancer) cell‐specific bioactivity and colonic metabolism and may guide future development of curcumin‐based chemopreventive agents after in vivo validation and metabolite characterization.