Daphnane diterpene esters with anti-proliferative activities against human lung cancer cells from Daphne genkwa

Two new daphnane-type diterpene esters, yuanhuahine (1) and yuanhualine (2), were isolated from the flowers of Daphne genkwa (Thymelaeaceae) along with three known diterpene esters, yuanhuacine (3), yuanhuadine (4), and yuanhuagine (5). Their structures were determined by a combination of 1D and 2D NMR experiments, including correlation spectroscopy (COSY), heteronuclear multiple quantum correlation (HMQC), heteronuclear multiple bond correlation (HMBC), and rotating frame Overhauser enhancement spectroscopy (ROESY) sequences, and mass spectrometry. All the isolated compounds were tested against A549 human lung cancer cells and MRC-5 human normal lung epithelial cells. Compounds 1-5 exhibited potent anti-proliferative effects against A549 lung cancer cells with IC50 values of 12-53 nM, whereas these compounds were relatively non-cytotoxic against MRC-5 normal lung epithelial cells.