Phorbasterones A-D, cytotoxic nor-ring A steroids from the sponge Phorbas amaranthus.

@article{Masuno2004PhorbasteronesAC,
  title={Phorbasterones A-D, cytotoxic nor-ring A steroids from the sponge Phorbas amaranthus.},
  author={Makoto N. Masuno and Joseph R. Pawlik and Tadeusz F Molinski},
  journal={Journal of natural products},
  year={2004},
  volume={67 4},
  pages={731-3}
}
The sponge Phorbas amaranthus from Florida contains the new ring A-contracted steroids, phorbasterones A-D, and the known anthosterones A and B. The structures of phorbasterones A-D were determined by interpretation of their spectroscopic data. Phorbasterones show moderate cytotoxicity against HCT-116 tumor cells.