Two new limonoid glycosides from the seeds of Citrus Limon and their PDE4D inhibitory activities.

Two new limonoid glycosides, named limonosides A ( 1 ) and B ( 2 ), along with four known limonoids ( 3 - 6 ) were obtained from the seeds of Citrus limon . Their structures were deduced based on extensive spectroscopic analysis. Limonoside A ( 1 ) and nomilin ( 4 ) were found to possess moderate phosphodiesterase type 4D (PDE4D) inhibitory effect with values of 89.8 ± 2.4% and 98.9 ± 3.0% at 10 μM, respectively.