Antibacterial hydroperoxysterols from Xanthosoma robustum.

Three new hydroperoxysterols, 24-hydroperoxy-4 alpha, 14 alpha- dimethylcholesta-8,25-dien-3 beta-ol, 25-hydroperoxy-4 alpha, 14 alpha-dimethylcholesta-8,23-dien-3 beta-ol and 25-hydroperoxycycloart-23-en- 3 beta-ol, have been isolated from the aerial parts of Xanthosoma robustum, besides 24-hydroperoxycycloart-25-en-3 beta-ol, 4 alpha, 14 alpha-dimethylcholesta-8,24-dien-3 beta-ol and cycloartenol. Additionally, the two new diols, 4 alpha, 14 alpha-dimethylcholesta-8,25-dien-3 beta, 24-diol and 4 alpha, 14 alpha-dimethylcholesta-8,23-dien-3 beta, 25-diol were obtained from the first two hydroperoxysterols, respectively, by reduction with triphenylphosphine. The structures have been defined by chemical and spectroscopic studies. The four hydroperoxysterols exhibited antibacterial activities against Escherichia coli, Bacillus subtilis and Micrococcus luteus.