Antiacetylcholinesterase triterpenes from the fruits of Cimicifuga yunnanensis

Abstract

Two new cycloartane triterpenes, cimyunnin E (1), containing a unique oxaspiro[4.4]nonanedione moiety based on rings D and E, together with cimicifine B (2), a 25,26,27-trinortriterpene featuring a pyridine ring E, were purified from the fruits of Cimicifuga yunnanensis. Their structures were elucidated by spectroscopic methods and ECD (electronic circular dichroism calculations). Compounds 1 and 2 showed significant acetylcholinesterase (AChE) inhibition with IC₅₀ values of 1.58 and 3.87 μM, respectively. In addition, they noticeably enhanced the neurite outgrowth of nerve growth factor (NGF) mediated PC12 cells at a concentration of 10 μM.

Fig. 1. Structures of compounds 1 and 2.

Fig. 2. Major HMBC (), ¹H–¹H COSY (), and ROESY () correlations of compound 1.

Fig. 3. The Newman projection of C-23/C-24 coupling system of 1.

Fig. 4. Calculated ECD spectra for -(17S,20R,23R,24S)-1 (red dashed line) and -(17R,20S,23S,24R)-1 (blue dashed line). Experimental CD spectrum of 1 (black solid line).

Fig. 5. Major HMBC (), ¹H–¹H COSY (), and ROESY () correlations of compound 2.