A new lanostane triterpenoid, 2-hydroxy-24-methylenelanostan-1,8-dien-3-one named klainedoxalanostenone (1) with one new steroid, 6-O-acyl-β-d-glucosyl-β-sitosterol named klainedoxasterol (2) together with ten known compounds including six triterpenoids (3-8), two steroids (9, 10) and two tanins (11, 12) were isolated from the stem bark of Klainedoxa gabonensis. To the best of our knowledge, this is the first report of lanostane-type triterpenoids from this genus. Their structures were determined by extensive analysis of spectroscopic data (1D and 2D NMR, MS) and by comparison with literature data. The xanthine oxidase inhibitory activity of nine compounds (1-6, 8, 10 and 11) were evaluated. Compound 5 showed a good xanthine oxidase inhibitory activity; the other tested compounds were moderately active.
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