Immunomodulatory and antitumour bioactive labdane diterpenoids from Leonurus japonicus.

Objectives Two labdane diterpenoids, leojapone B and heteronone B, were isolated fromLeonurus japonicusHoutt., and their biological activity were evaluated in this study. Methods Human and mouse cancer cells, human peripheral blood mononuclear cells (PBMCs) and mouse macrophages (RAW264.7 cells) were used to evaluate the activity of leojapone B and heteronone B, while thein vivoeffects of leojapone B were further examined in Lewis Lung Cancer tumour-bearing mice. Key findings In vitrostudies showed that leojapone B selectively inhibited the proliferation of lung cancer cells, and both leojapone B and heteronone B inhibited the production of pro-inflammatory cytokines in activated PBMCs. In tumour-bearing mice model, lung tumours were reduced in size in mice treated with intraperitoneal injections of leojapone B at 20 and 30 mg/kg for 14 days. The population ratio of CD4(+)/CD8(+)T cells in mouse spleens was found to be increased, while regulatory T cells were decreased after leojapone B treatment. Conclusions The inhibitory effects of leojapone B in mouse lung tumours were demonstrated for the first time in this study. The immunomodulatory activity of heteronone B were also demonstrated. Our findings indicated that both leojapone B and heteronone B may act as active components inL. japonicus.