The uterotonic activity of compounds isolated from the supercritical fluidextract of Ekebergia capensis

The wood of Ekebergia capensis Sparrm. is used by the local Zulu community in KwaZulu-Natal Province, South Africa to facilitate childbirth. In this i nvestigation, the uterotonic properties of extracts from this tree were eva luated using both pregnant and non-pregnant guinea pig uterine smooth muscl e in vitro. The extracts were prepared using water modified supercritical c arbon dioxide at 400 atm and 80 degreesC. As samples of these extracts disp layed positive results when screened for uterotonic activity, gravity colum n chromatography followed-by NMR spectroscopy was performed in an attempt t o isolate and elucidate the structures of the compounds that were present i n the extract. The extract yielded five known compounds of which only two, viz. oleanonic acid and 3-epioleanolic acid, displayed uterotonic activity. Receptor binding assays were subsequently performed with 3-epioleanolic ac id to ascertain its mode of action. Bradykinin (30 ng/100 mul) and acetylch oline (1 mug/100 mul) were used as the B2 and cholinergic receptor agonists respectively with icatibant (HOE 140) (30 ng/100 mul) and atropine (60 mu /100 mul) as their corresponding antagonists. 3-epioleanolic acid was obser ved to mediate its effect through the cholinergic receptor. The results of this study show that two compounds from the extract of this tree possess va rying degrees of agonist activity on uterine smooth muscle with minor chang es in the molecular structure affecting its intrinsic activity on uterine m uscle. (C) 2000 Elsevier Science B.V. All rights reserved.