Synthesis and anti-hepatocellular carcinoma evaluation of salicylic acid-modified indole trimethoxy flavonoid derivatives

Simultaneous inhibition of tumor vasculature and the glycolysis pathway may be a targeted anti-tumor strategy to inhibit tumor nutrient supply. Flavonoids are natural products with strong biological activity, which inhibit hypoxia induction factor 1α (HIF-1α) regulating glycolysis and tumor angiogenesis, while salicylic acid can reduce the glycolysis level of tumor cells by inhibiting related rate-limiting enzymes. A series of salicylic acid-modified indole trimethoxy-flavone derivatives were designed and synthesized by introducing benzotrimethoxy-structure commonly used in blood vessel blockers, and their anti-tumor activities were evaluated. Among them, compound 8f exhibited significant anti-proliferative activity against two hepatoma cells, HepG-2 and SMMC-7721, with IC50 values of 4.63 ± 1.13 μM and 3.11 ± 0.35 μM, respectively. Colony formation experiments also further verified its excellent in vitro anti-tumor activity. In addition, compound 8f showed the ability to induce apoptosis in SMMC-7721 cells in a concentration-dependent manner. After treatment with compound 8f, the expressions of the rate-limiting enzymes PKM2, PFKM, HK2 and tumor angiogenesis-related vascular endothelial growth factor of the glycolytic pathway were all down-regulated, and the lactate level in the hepatoma cell SMMC-7721 was significantly reduced. The morphology of the nucleus and tubulin was also observed to disperse gradually with the increase of compound 8f concentration. And compound 8f showed strong binding ability to tubulin. Our results suggest that the strategy of synthesizing the salicylic acid-modified indole flavone derivative 8f is a way to obtain active anti-tumor candidate compounds that may be further developed as targeted agents to inhibit tumor vasculature and glycolytic pathways.