Triterpenoids from the roots of Pterospermum heterophyllum Hance

Abstract

Two new triterpenoids taraxer-14-ene-1α,3β-diol (1) and 3β-hydroxytaraxer-14-ene-1-one (2), together with the known triterpenes taraxerol (3), betulin (4), betulinic acid (5), sumaresinolic acid (6), and 5-hydroxy-2-methoxy-1,4-naphthoquinone (7), 5,7-dihydroxy-6,8-dimethylchromone (8), α-monpalmitin (9), palmitic acid (10), 6β-hydroxystigmast-4-en-3-one (11), β-sitostero1 (12), have been isolated from the petroleum ether fraction of the ethanolic extract of Pterospermum heterophyllum. Their structures were established by spectroscopic methods including IR, MS, 1D, and 2D NMR experiments. Compounds 1–8 were evaluated against several human cancer cell lines. Compound 1 showed in vitro selective cytotoxicity against human lung cancer cell lines (A549) with an IC₅₀ value of 1.22 μM. Compound 7 showed significant cytotoxicity against the A549, HCT-8, Bel7402, BGC-823, and A2780 cancer cell lines with IC₅₀ values of 0.21, 0.55, 0.40, 0.59, and 0.34 μM, respectively. However, the other compounds were inactive (IC₅₀>10 μM).

Keywords:

• Pterospermum heterophyllum
• Sterculiaceae
• triterpenoid
• naphthoquinone
• cytotoxic activity

Acknowledgements

This research was supported by the Key Laboratory of Bioactive Substances and Resources Utilization of Chinese Herbal Medicine, Ministry of Education. We thank Ms Wu Yan for the NMR and Mr Zeper Abliz for the EI-MS and HR-EI-MS measurements.