Cytotoxic activities of Telectadium dongnaiense and its constituents by inhibition of the Wnt/β-catenin signaling pathway

Background Wnt/β-catenin signaling pathway is a potential target for the treatment of human colon cancer. Thus, the inhibitory effects of various plant extracts on cell proliferation and Wnt signal transduction were evaluated to discover a Wnt signaling inhibitor. Purpose The present study aimed to investigate the cytotoxicity involved in Wnt pathway of the MeOH extract from Telectadium dongnaiense bark (TDB) and to identify its bioactive constituents by bioassay-guided fractionation. Methods The sulforhodamine B-based proliferation assay and the β-catenin/TCF-responsive reporter gene assay were employed as screening systems. The isolation and identification of compounds were elucidated on the basis of spectroscopic methods. Inhibitory effects on the expression levels of Wnt target genes were determined by real-time PCR and western blotting. Results The extract of TDB most strongly inhibited cell proliferation and TOPflash activity (IC₅₀ = 1.5 and 2.0 µg/ml), which was correlated with its inhibitory effects on the expression of Wnt target genes. Three major compounds were isolated from bioactive fractions and were identified as 1,4-dicaffeoylquinic acid (1), quercetin 3-rutinoside (2), and periplocin (3). Only compound 3 showed anti-proliferative activity (IC₅₀ = 0.06 µM) and exhibited Wnt signaling inhibitory effects in HCT116 colon cancer cells. Conclusions This study contributes to understanding the cytotoxic properties of TDB extract and its constituents and provides a potent strategy for its further application.