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.