New monoterpenes from Mentha microphylla

Four new monoterpenes, (1 R*,2 S*)-1,2-dihydroxy- p-menth-4(8)-en-3-one ( 1), (4 S*)-4-hydroxy- p-mentha-1,8-dien-3-one ( 2), (4 S*)-4-methoxy- p-mentha-1,8-dien-3-one ( 3), and (3 R*,4 R*,6 S*)-3-acetoxy-6-hydroxy- p-mentha-1,8-diene ( 4) together with four known compounds have been isolated from the aerial parts of Mentha microphylla. The structures were determined using spectroscopic methods particularly high resolution (1)H-, (13)C-NMR as well as 2D (1)H- (1)H COSY, HMQC and HMBC analysis.