Five new alkaloids from Coptidis Rhizoma–Euodiae Fructus couple and their cytotoxic activities against gastrointestinal cancer cells

A new indoloquinazoline alkaloid, 10-methoxywuchuyuamide I (1), three new benzylisoquinoline alkaloids, named as coptichic aldehyde (2), coptichine (3) and 13-carboxaldehyde-8-oxocoptisine (4), and a new isoindoline alkaloid, named as coptichinamide (5), together with two known alkaloids, wuchuyuamide I (6) and 8-oxocoptisine (7) were isolated from the Coptidis Rhizoma–Euodiae Fructus couple. Their chemical structures were determined by extensive spectroscopic analyses, including IR, UV, EI–MS, HRESI–MS, 1D and 2D NMR data (¹H NMR, ¹³C NMR, ¹H–¹H COSY, HSQC and HMBC). Cytotoxicities of the isolated alkaloids against NCI-N87 and Caco-2 cell lines were evaluated. Four benzylisoquinoline alkaloids 2–4 and 7 showed inhibitory activities against NCI-N87 cell with IC₅₀ values range from 8.92 to 35.98 μM. The alkaloid 3 was a new antiproliferation compound against NCI-N87 cells. The results provided valuable information for further investigation of alkaloid 3 as a chemopreventive agent.