Further screening of the resin glycosides in the edible water spinach and characterisation on their mechanism of anticancer potential

• Eight new resin glycosides were isolated form water spinach.
• 1, 2 and 4 exhibited potent cytotoxic activities.
• Aquaterin II induced G0/G1 arrest and mitochondria-mediated apoptosis.
• Aquaterin II inhibited the PI3K/Akt signalling pathway.

Water spinach (I. aquatica) is one of the common green leafy vegetables used in Asia. In a continuing chemical investigation on the cytotoxic resin glycosides from water spinach, eight new resin glycosides, Aquaterins XII–XIX (1–8), were isolated, among which 1, 2 and 4 exhibited potent cytotoxic activities. To further characterise the anticancer potential of the resin glycosides from water spinach, Aquaterin II obtained previously was investigated on HepG2 cells. The results showed that Aquaterin II induced G0/G1 arrest regulated by related proteins CDK4/6, cyclin D/E and p21, and caused mitochondria-mediated apoptosis featured by MMP decrease, ROS accumulation, caspase cascade activation and Bax/Bcl-2 alteration. Additionally, the suppression on PI3K/Akt signalling pathway was observed, suggesting that it participated in the Aquaterin II-induced cell growth inhibition. Our results are the first to demonstrate the antiproliferative mechanism of resin glycosides. This investigation also advanced the potential application of water spinach as a functional food.