A new antimycobacterial, 3β-acetoxy-15α,22-dihydroxyhopane, from the insect pathogenic fungus Aschersonia tubulata

Bioassay-guided fractionation of the cell extract of the insect pathogenic fungus Aschersonia tubulata BCC 1785 led to the isolation of dustanin (1), 3 beta ,15 alpha ,22-trihydroxyhopane (3), 5 alpha ,8 alpha -epidioxy-24(R)-methylcholesta-6,22-diene-3 beta -ol (6), together with the new 3 beta -acetoxy-15 alpha ,22-dihydroxyhopane (4). Chemical structures of these compounds were elucidated by spectral analyses as well as chemical transformation. Compounds 1 and 4 exhibited antimycobacterial activity with the minimum inhibitory concentration (MIC) of 12.5 mug/ml.