Bungsteroid A: One Unusual C34 Pentacyclic Steroid Analogue from Zanthoxylum bungeanum Maxim

Bungsteroid A (1), possessing an unreported carbon skeleton, was isolated from the pericarps of Zanthoxylum bungeanum Maxim. It represents the first carbon skeleton of a C-34 steroid analogue featuring a unique 6/6/6/6/5-fused pentacyclic skeleton, which has been determined by spectroscopic methods, quantum-chemical C-13 NMR, ECD calculations, and calculations of optical rotations. Bungsteroid A showed the antiproliferative effects against HepG2, MCF-7, and HeLa cell lines with the IC50 values of 56.3 +/- 1.1, 64.2 +/- 0.9, and 74.2 +/- 1.3 mu M, respectively.