New clerodane diterpenoid glycosides from the aerial parts of Nannoglottis carpesioides.

Three new clerodane diterpenoid glycosides with L-arabinose (1-3), together with ten known compounds including phytol-type diterpenes, cycloartane-type, ursane-type, and oleanane-type triterpenes, were isolated from the aerial parts of Nannoglottis carpesioides which a Chinese endemic genus. The structures of the new compounds 1-3 were identified based on chemical and spectroscopic studies, including one- and two-dimensional NMR, HRESIMS, UV, and IR results. Their absolute configurations were determined by the application of theory calculations of optical rotation, which were compared with the experimental data. New aglycone 1a and L-arabinose were obtained by acid hydrolysis of 1 and GC-MS analysis. The cytotoxicities of some isolated compounds against a panel of human cancer cell lines were evaluated by the MTT assay. Clerodane diterpenoides are the characteristic chemical constituents and may be used as chemical markers of the genus Nannoglottis.