Cholinesterase Inhibiting Activity and A New Piperidine Alkaloid from Lobelia laxiflora L. Roots (Campanulaceae)

The total alkaloidal fraction of Lobelia laxiflora L. roots was tested for cholinesterase inhibiting activity using spectrophotometric method. The IC 50 value of the alkaloidal fraction recorded was close to that of eserine ( 286.3 µg/mL and 270 µg/mL, respectively) . This biologically active alkaloidal fraction was subjected to a phytochemical study to isolate and identify its major constituents. Two piperidine alkaloids, N-methyl-2(2 ' -methoxybutyl),6(2 '' -hydroxybutyl)- Δ 3 -piperidine (1) and N-methyl- 2(2 ' -hydroxybutyl),6(2 '' -hydroxybutyl)- Δ 3 -piperidine (2), were isolated. The structures of the two compounds were established based on their spectral data, including MS, 1H- and 13C-NMR, COSY, HMQC and HMBC spectral experiments. Compound (1) is a new natural compound while compound (2) was previously isolated from the aerial parts of the same plant.