Two new neo-clerodane diterpenoid alkaloids from Scutellaria barbata with cytotoxic activities

Abstract

Two new neo-clerodane diterpenoid alkaloids, scutebarbatine O (1) and 6-O-nicotinoylscutebarbatine G (2), were isolated from the whole plant of Scutellaria barbata. Their structures were elucidated by spectroscopic methods including extensive 1D and 2D NMR analyses. In vitro, compounds 1 and 2 showed cytotoxic activities against three human tumor cell lines, namely, HONE-1 nasopharyngeal, KB oral epidermoid carcinoma, and HT29 colorectal carcinoma cells, and with IC₅₀ values in the range of 2.1–5.7 μM.

Keywords:

• Scutellaria barbata D. Don
• neo-clerodane diterpenoid alkaloid
• scutebarbatine O
• 6-O-nicotinoylscutebarbatine G
• cytotoxic activity

Acknowledgements

We are grateful to Mr Yong Li, Ji-Yong Chen, and Ms Hong Yu (School of Pharmaceutical Science, Yantai University) for the measurement of FAB-MS, HR-FAB-MS, UV, IR, and NMR spectra, respectively. We also gratefully acknowledge Mr Zhen-Hua Wang and Ms Ming Yang (School of Pharmaceutical Science, Yantai University) for the bioactivity screenings.