Ionone derivatives from Alternanthera sessilis

The chloroform extract of the air-dried leaves of Alternanthera sessilis afforded a mixture of diastereomers of a new ionone derivative 1 whose structures were elucidated by extensive 1D and 2D NMR spectroscopy and mass spectrometry. Oxidative clevage of 1 to aldehyde 3 with manganese dioxide confirmed diastereoisomerism arose from a racemic slide chain chiral centre. Antimicrobial tests on the mixture of diastereomers and the derivative indicated that they have low activities against Pseudomonas aeruginosa and Trichophyton mentagrophytes.