Eighty-one constituents were newly identified from the oil of Mentha piperita L., including a new keto-alcohol, (-)-mintlactone and (+)-isomintlactone. They were determined by spectral data and syntheses to be 4-hydroxy-4-methyl-2-cyclohexen-l-one (8), (6R, 7aR) (10) and (6R, 7aS)-3, 6-dimethyl-5, 6, 7, 7a-tetrahydro-2 (4H)-benzofuranone (11), respectively.
