Scutellarin derivatives as apoptosis inducers: Design, synthesis and biological evaluation

To explore novel antitumor agents with high efficiency and low toxicity, a series of NO-donating scutellarin derivatives (14-17) were synthesized and the antiproliferative activities against MCF-7, HCT-116, PC-3 and HepG2 cancer cell lines were assessed. Among them, compound 14b was the strongest with IC₅₀ values of 2.96 μM, 7.25 μM, 0.09 μM and 0.50 μM, respectively, and displayed low toxicity against normal human liver L-O2 cells with an IC₅₀ of 47.96 μM, showing good selectivity between normal and malignant liver cells. Moreover, NO releasing ability of the derivatives has been studied. Mechanism studies of the most promising compounds 14b and 15a were carried out. The results indicated that 14b and 15a could induce apoptosis, cell cycle arrest at the S phase and led to mitochondrial dysfunction in the HepG2 and PC-3 cell lines, respectively. Furthermore, Human Apoptosis Protein Array kit assay demonstrated that 14b could induce apoptosis through down-regulating the levels of procaspase-3 and inhibiting the expression of survivin, c-IAP1, HSP27, HSP60, HSP70, HO-1/HMOX1/HSP32 and HO-2/HMOX2 in HepG2 cell line. These results guaranteed compound 14b to be a drug candidate against liver cancer for further investigation.