Cytotoxic withanolides from the stems and leaves of Physalis ixocarpa

The stems and leaves of the tomatillo (Physalis ixocarpa or Physalis philadelphica) were considered agricultural waste during the processing of tomatillo fruits. However, their potential value for utilization has not yet been explored. The investigation resulted in the isolation of a total of 29 withanolides, out of which 15 never reported. These newly discovered withanolides were then tested for their cytotoxicity against eight different human tumor cell lines. Compounds 2-3, 6-7, 17, 19, and 25-27 displayed encouraging cytotoxic effects. Given the potent inhibitory activity of physagulin C (25) on the proliferation of HepG2 cells in vitro, further investigation was conducted to determine its molecular mechanism. Physagulin C inhibited epithelial-mesenchymal transition (EMT) process through the down-regulation of the JAK2/STAT3 and PI3K/AKT/mTOR pathways. Withanolides presenting in the stems and leaves of tomatillo make the plant possess potential commercial importance. Therefore, tomatillos could be commercialized worldwide in the food and pharmaceutical industries.