Swertiamarin fails to induce cytotoxicity in colon cancer cell lines: Evidence against a direct anticancer effect

Colorectal cancer (CRC) is the third most common cancer worldwide, with rising incidence linked to unhealthy lifestyle habits. Although 5-fluorouracil (5-FU) remains a standard therapy, its efficacy is often limited by resistance and adverse effects. These limitations have driven interest in plant-derived bioactive compounds as complementary or alternative therapies. This study investigated the potential anticancer effects of Swertiamarin (SWT), a seco-iridoid glycoside with reported anti-inflammatory and antioxidant properties.

Three human CRC cell lines (HT-29, HCT-116, and Caco-2) and a non-cancerous (Vero E6) cell line were treated with SWT sourced from three independent suppliers to ensure reproducibility. Cell viability was evaluated using Trypan blue exclusion and MTT assays, while scratch assay and microscopic analyses were used to assess migration and morphological changes. The antioxidant capacity of SWT was measured using hydrogen peroxide scavenging assays, and its antimicrobial activity was tested against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus).

SWT exhibited minimal or no effect on cell proliferation across all cell lines, concentrations, and time points, while 5-FU significantly reduced cell viability. Co-treatment with SWT and 5-FU did not enhance cytotoxicity, indicating no synergistic effect. SWT also had no impact on cell migration or morphology. However, it demonstrated strong antioxidant activity comparable to ascorbic acid and displayed antimicrobial effects, transiently inhibiting E. coli and persistently suppressing S. aureus.

SWT does not exert direct cytotoxic or antimigratory effects in CRC models but possesses potent antioxidant and antimicrobial activities. These findings suggest a possible chemopreventive or protective role for SWT rather than a therapeutic one. This study underscores the importance of rigorous and reproducible evaluation of pure natural products to accurately define their biological and therapeutic potential.