A combined experimental and theoretical study on weisiensin B with cytotoxicity

Weisiensin B is an ent-kaurane diterpenoid isolated from Isodon weisiensis C.Y. Wu. This natural product exhibits significant cytotoxicity against human Bel-7402 tumor cell. The molecular geometry, vibrational frequencies, gauge-including atomic orbital (GIAO) 13C chemical shift value in the ground state have been calculated by using HF and B3LYP level. The results of the optimized molecular structure are presented and compared with the experimental X-ray diffraction. The computed vibrational frequencies are used to determine the types of molecular motions associated with each of the experimental bands observed. Also, calculated 13C chemical shift values are compared with the experimental ones. A molecular electrostatic potential (MEP) map was used in an attempt to identify key features of the title compound to account for its anti-tumor activity. The results from comet assay had demonstrated that the title compound had stronger cytotoxicity and DNA damage potential. The growth inhibition activity of the title compound for Bel-7402 cells occurred in a time- and dose-dependent manner (IC50 was 15.42 ± 2.06 μM). The data generated in this study is valuable as it provides an insight into the title compound molecular and structure–activity relationships.