Nudifloids A-N, structurally diverse 3,4-seco-labdane diterpenoids from Callicarpa nudiflora with inflammatory inhibitory activity.

Fourteen undescribed seco -type diterpenoids, named nudifloids A-N, together with ten known analogs, were isolated from the leaves of Callicarpa nudiflora. Nudifloids A-N had a characteristic 3,4- seco -labdane-type diterpenoid skeleton, whereas nudifloids A-C and K–N were 3,4- seco -norditerpenoids. Nudifloid A was the first example of a 3,4- seco -12,13,14,15,16-quartnor-labdane diterpenoid, with a seven-membered lactone ring formed through esterification between C-3 and C-11. Nudifloids B and C were a pair of highly modified 3,4- seco -labdane nor-diterpenoid epimers, of which C-2 and C-18 were cyclized together to form a cyclohexene fragment. The structures of these undescribed diterpenoids were established by spectroscopic analysis and reference data. The anti-inflammatory activity of diterpenoids in rich yield was evaluated by analyzing the inhibition of lipopolysaccharide plus nigericin-induced pyroptosis in J774A.1 cells. Nudifloids D and E exhibited prominent anti-NLRP3 inflammasome activity, with IC 50 values of 1.80 and 1.59 μM, respectively. Cell permeability assays revealed that nudifloid D inhibited pyroptosis, which could ameliorate inflammation by blocking the activation of the NLRP3 inflammasome. Guiding by anti-inflammatory activity, fourteen undescribed 3,4- seco -labdane diterpenoids were isolated from the leaves of Callicarpa nudiflora , and evaluated the anti-inflammatory activity of abundant diterpenoids. [Display omitted] • Bioassay-guided isolation of C. nudiflora to obtain twenty-four seco -diterpenoids. • Of which, fourteen undescribed 3,4- seco -labdane diterpenoids were determined. • Nudifloid A exhibits the first example with a seven-numbered lactone ring. • Nudifloids D and E exhibited prominent inflammatory inhibitory activity. [ABSTRACT FROM AUTHOR]