neo-Clerodane diterpenes from Ajuga ciliata Bunge and their neuroprotective activities.

Three new (1-3) and three known (4-6) neo-clerodane diterpenes have been isolated from the whole plants of Ajuga ciliata Bunge. The structures of the new compounds were elucidated as (12S)-1β,6α,19-triacetoxy-18-chloro-4α,12-dihydroxy-neo-clerod-13-en-15,16-olide (1), (12S,2'S)-12,19-diacetoxy-18-chloro-4α,6α-dihydroxy-1β-(2-methylbutanoyloxy)-neo-clerod-13-en-15,16-olide (2), and (12S)-6α,18,19-triacetoxy-4α,12-dihydroxy-1β-tigloyloxy-neo-clerod-13-en-15,16-olide (3), on the basis of spectroscopic data analysis. All the diterpenes were evaluated for the neuroprotective effects against MPP(+)-induced neuronal cell death in dopaminergic neuroblastoma SH-SY5Y cells and compounds 2-5 exhibited moderate neuroprotective effects.