Supercritical fluid extraction and analysis of indigenous medicinal plants for uterotonic activity.
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Date
1997
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Abstract
Ingestion of extracts prepared from various medicinal plants to induce or augment labour
is common amongst Black South African women during the late stages of pregnancy.
This applies particularly to the rural areas where modern health care facilities are often
lacking. Many of these plants have not been investigated scientifically and one needs to
substantiate claims of quality, safety and efficacy. Furthermore, it is believed that the
consumption of these plant extracts can result in foetal meconium staining at delivery.
An investigation into the uterotonic properties of three plants viz. Ekebergia capensis
Sparrm. Clivia miniata (Lindl.) Regel. and Grewia occidentalis L. were carried out using
guinea pig uterine smooth muscle in vitro. Supercritical fluid extraction was performed
with water modified supercritical carbon dioxide to extract the uterotonic components.
An attempt was also made to couple supercritical fluid extraction directly on-line to the
bioassay so that on line screening of crude plant extracts could be performed within short
periods of time. The effects of supercritical CO2 decompression on temperature and pH of
the muscle bathing solution were considered since these factors affect muscle
contractility. The direct effects of excess CO2 on intracellular mechanisms were
eliminated by constructing a CO2 reduction interface together with passage of carbogen
which aided in the rapid displacement of excess CO2, As samples of these extracts were
found to induce muscle contraction, supercritical fluid fractionation (SFF) was performed
by sequentially increasing the fluid density. Extracted fractions were obtained by
sequentially increasing the pressure at constant temperature and modifier concentration in
an attempt to identify the active fractions. Extractions were performed at 200 atm, 300
atm and 400 atm respectively. Subsequent testing of these fractions enabled the detection
of active and inactive fractions as well as a fraction that had a spasmolytic effect on
uterine muscle. The 400 atm extracts of E. capensis and C. miniata displayed maximum
activity while only the 300 atm extract of G. occidentalis induced uterine muscle
contraction. Subsequent analysis of the sequentially extracted fractions, by high
performance liquid chromatography and micellar electrokinetic capillary chromatography
revealed that certain compounds present in the fractions that stimulated muscle
contraction, were sensitive to the extraction pressure hence making it possible to
determine the compounds that were likely to be active. Column chromatography
followed by various spectroscopic techniques were performed in an attempt to isolate and
elucidate the structures of the compounds that were present in the plant extracts. The
extract of Ekebergia capensis yielded five known compounds (B-sitosterol, oleanonic
acid, 3-epioleanolic acid, 2,3,22,23-tetrahydroxy-2,6,1 0, 15,19 ,23-hexamethyl-6, 10, 14, 18-
tetracosatetrene and 7-hydroxy-6-methoxy coumarin. The extract of Clivia miniata
yieded linoleic acid and 5-hydroxymethyl-2-furancarboxaldehyde while the extract of
Grewia occidentalis yielded 3-(4-hydroxy-3-methoxyphenyl)-2-propenal, a novel
compound 2,2' ,6,6'-tetramethoxy-4'-al-4-(w-oxo-E-propenyl)-biphenyl and oleanonic
acid. The pure compounds were further evaluated pharmacologically to identify the
active components and assess the physiological mode of action by the use of various
receptor blockers. Oleanonic acid, 3-epioleanolic acid, linoleic acid and 5-
hydroxymethyl-2-furancarboxaldehyde and 3-(4-hydroxy-3-methoxyphenyl)-2-propenal
were found to induce an agonistic muscle response. All these compounds were observed
to mediate their effects through the cholinergic receptors. The results obtained in this
study supports the claim of these plants possessing uterotonic properties.
Description
Thesis (Ph.D.)-University of Natal, Durban, 1997.
Keywords
Supercritical fluid extraction., Medicinal plants--Analysis., Meliaceae., Amaryllidaceae., Tiliaceae, Labour, Induced (Obstetrics), Traditional medicine--South Africa., Theses--Chemistry.