Objective To investigate the chemical constituents from the twigs and leaves of Alstonia mairei and to evaluate their antifungal activity. Methods The separation and purification were conducted by a variety of chromatographic separation techniques, including MCI, silica gel, Sephadex LH-20 gel column chromatography, and preparative high-performance liquid chromatography. The chemical structures of the isolated compounds were elucidated by spectroscopic methods, including mass spectrometry, nuclear magnetic resonance, and electronic circular dichroism (ECD). The antifungal activity of the selected compounds was evaluated against Candida albicans CMCC98001 and Aspergillus niger R330 using the microbroth dilution method. Results A total of eight compounds were isolated from the twigs and leaves of A. mairei, including one new compound, ent-12-hydroxy-16-methylol-atisane-3-one (1), and seven known compounds, 17-acetylsarpagine (2), 1,2,3,4-tetrahydro-1-oxo-β-carboline (3), vinorine N₄-oxide (4), vinorine (5), yohimbine (6), hancockinol (7), ent-16β, 17-dihydroxyatlsan-3-one (8). The MICs of compound 1 and 8 against A. niger R330 were 12.5 and 6.25 μg/mL, respectively. Conclusion Compound 1 is a new diterpenoid named alstomanoid A, and compounds 3, 7 and 8 are isolated from the genus of A. mairei for the first time. Compounds 1 and 8 show antifungal effect against A. niger R330.

Alstonia mairei Lévl.  /  diterpenoid  /  alkaloids  /  antifungal activity  /  alstomanoid A  /  1,2,3,4-tetrahydro-1-oxo-β-carboline  /  hancockinol  /  ent-16β,17-dihydroxyatlsan-3-one