Triterpenes from the button cactus, Epithelantha micromeris.

Ethanolic extracts of the title plant were toxic to mice. Acid hydrolysis of the toxic extracts permitted the isolation of six crystalline compounds. The known triterpenes oleanolic acid and methyl machaerinate and the common plant sterol, beta-sitosterol, were identified. The structures of two other isolated compounds, named epithelanthic acid and methyl epithelanthate, were postulated to be new delta9(11)-12-oxooleanenes, and another trace compound was incompletely categorized as a triterpene lactone.