Two new phenolic acid helisterculins C (1) and D (2) were isolated from the whole plant of Clerodendranthus spicatus. Their structures were elucidated on the basis of 1D and 2D NMR, MS, and CD analysis. Compound 1 possesses an unusual bicyclol [2. 2. 2] octane moiety which is rare in the previously isolated phenolic acid derivatives. The two compounds were tested in vitro for neuroprotective activities against 6-OHDA-induced cell death in SH-SY5Y cells, and the result showed that compounds 1 and 2 displayed moderate neuroprotective activity with the IC50 values of 17.4 and 21.3 μM, respectively.
Keywords: Clerodendranthus spicatus; Lamiaceae; helisterculins C and D; neuroprotective activity; phenolic acids.