Two new cytotoxic diterpenoid alkaloids from Delphinium grandiflorum

Delphinium grandiflorum, one of the well-known Delphinium species, contains diverse bioactive diterpenoid alkaloids (DAs), which promoted a systematic phytochemical study on this plant. As a result, two new DAs, namely 16-demethyl tuguaconitine (1) and 6-O-acetyl-16-demethyldelsoline (2), together with one known analogue pseudophnine A (3) were obtained from the whole herbs of D. grandiflorum. Their structures were elucidated by use of extensive spectroscopic analysis (HR-ESIMS, IR, 1D and 2D NMR). Additionally, the inhibitory effects of these obtained individual compounds were also evaluated in vitro for lung cancer cell line (A549), liver cancer cell line (SMMC-7721), and breast cancer cell line (MCF-7). The results of cytotoxic activities showed that only compound 2 exhibit weak inhibitory effect on SMMC-7721 and MCF-7, and their IC50 values were 37.4 and 33.1 mu M, respectively. However, compound 1 and 3 had no obvious cytotoxic activities (IC50>80 mu M).