Coupling SFE to uterotonic bioassay: an on-line approach to analysing medicinal plants

Supercritical fluid extraction has been directly coupled on-line to a utero tonic bioassay, using guinea pig uterine smooth muscle in vitro. This techn ique was developed for the detection of uterotonic compounds present in med icinal plants used during pregnancy to induce or augment labour. The direct passage of CO2 into the muscle chamber led to adiabatic cooling of the phy siological fluid and inhibition of muscle contraction. This was alleviated by the construction of a CO2 reduction interface together with the passage of carbogen which aided in the rapid displacement of excess CO2. The on-lin e system was evaluated with four plants (Clivia miniata (Lindl.) Regel, Eke bergia capensis Sparrm., Grewia occidentalis L. and Asclepias fruticosa L.) that are currently used during pregnancy by some black South African women . Extractions were performed with water modified supercritical CO2. Fractio ns of supercritical fluid extracts, obtained by sequentially increasing the pressure from 200 to 300 and 400 atm at constant temperature were transfer red directly to the muscle chamber to identify the active fractions. The 40 0 atm extracts of C. miniata, A. fruticosa and E. capensis displayed maximu m uterotonic activity while only the 300 atm extract of G. occidentalis ind uced uterine muscle contraction. This technique proved to be a safe and sen sitive method for analyzing medicinal plants that contain uterotonic substa nces hence assisting in rapidly validating the uterotonic properties and de tecting any toxic effects of these extracts. (C) 1998 Elsevier Science B.V. All rights reserved.