Constituents of Senecio chionophilus with potential antitubercular activity.

Two new sesquiterpenoids, (1S,4S,5R,10R)-1-hydroxy-6-isobutyryloxy-10H-9-oxofuranoeremophilane (1) and 1alpha-hydroxy-6beta-(2xi-methylbutyryloxy)-10alphaH-9-oxofuranoeremophilane (2), along with 21 known constituents, were isolated from the n-hexane and dichloromethane extracts of the above-ground biomass and roots of Senecio chionophilus. The structures of 1 and 2 were elucidated on the basis of spectroscopic evidence and chemical transformation methods. The absolute configuration of 1 was determined by Mosher ester methodology. All of the isolates were evaluated for their antitubercular potential against Mycobacterium tuberculosis in a microplate Alamar Blue assay. Compound 2, 6beta-angeloyloxy-1alpha-hydroxy-10alphaH-9-oxofuranoeremophilane (3), and 4'-hydroxyacetophenone (6) exhibited mild antitubercular activity at minimum inhibitory concentrations of 119, 114, and 121 microg/mL, respectively.