Estudio termodinámico de la solubilidad de algunas sulfonamidas en mezclas cosolventes

Se determinó la solubilidad de sulfadiazina, sulfamerazina y sulfametazina en diferentes mezclas cosolventes n-alcohol + agua entre 293,15 K y 313,15 K, y se calcularon las respectivas funciones termodinámicas de solución. Los parámetros de solvatación preferencial de los fármacos se derivaron a partir de sus propiedades termodinámicas de solución por medio de los métodos de las integrales inversas de Kirkwood-Buff (Inverse Kirkwood-Buff integrals IKBI) y cuasi-reticular cuasi-químico (Quasi-Lattice Quasi-Chemical, QLQC). A partir de los estudios acerca del efecto del solvente, se encontró que estos fármacos son sensibles a los efectos específicos de solvatación preferencial. El para ́metro de solvatación preferencial por metanol, δx1,3, es negativo en mezclas ricas en agua pero positivo en los demás casos, y en el caso de los otros alcoholes (etanol y n-propanol) el parámetro de solvatación preferencial es negativo en mezclas ricas en agua al igual que en mezclas ricas en el n-alcohol, y positivo en mezclas de composiciones intermedias. Es conjeturable que, en mezclas ricas en agua la hidratación hidrofóbica en torno a los anillos aromáticos y/o grupos metilo juega un papel relevante en la solvatación de los fármacos, mientras que en mezclas ricas en etanol y n-propanol, el parámetro de solubilidad podría estar influenciando en mayor proporción la hidratación de los fármacos. Se observaron relaciones entálpicas-entrópicas no lineales al graficar la entalpía en función de la energía de Gibbs de solución. Las gráficas ∆solnH0 vs. ∆solnG0 muestran dos tendencias diferentes en función de la pendiente obtenida, una pendiente negativa indica una conducción entrópica y una pendiente positiva indica una conducción entálpica. Por otro lado, se observó la relación de entalpía-entropía lineal en una gráfica de entalpía frente a la entropía de la solución también, en este caso la pendiente superior a uno indica que el mecanismo de conducción es la entalpía y la pendiente inferior a uno indica que el mecanismo de conducción es la entropía De otro lado, los valores estimados de solubilidad, obtenidos mediante el uso de modelos semiempíricos presentan desviaciones notables con respecto a los valores experimentales. Estos resultados demostraron la necesidad de mejorar las estrategias teóricas para estimar esta propiedad, demostrando además la gran importancia de la determinación experimental de la solubilidad de los fármacos en aquellas mezclas cosolventes útiles en métodos de purificación y en el diseño de formas de dosificación.Abstract. The equilibrium solubility of sulfadiazine, sulfamerazine and sulfamethazine in different n- alcohol + water binary mixtures at temperatures from 293.15 K to 313.15 K was determined and the respective thermodynamic quantities of solution were calculated. Additionally, the preferential solvation parameters of the drug were derived from their thermodynamic solu- tion properties by means of the inverse Kirkwood-Buff integral (IKBI) and the quasi-lattice quasi-chemical (QLQC) methods. From solvent effect studies, it was found that these drugs are sensitive to specific solvation effects. The preferential solvation parameter by methanol, δx1,3 is negative in water-rich but positive in other mixtures; otherwise, in the case of the others two alcohols (ethanol and n-propanol) the preferential solvation parameter is negative in water-rich mixtures and n-alcohol-rich too, and positive in mixtures of intermediate compositions. It is conjecturable that in water-rich mixtures the hydrophobic hydration around aromatic rings and/or methyl groups plays a relevant role in the drug solvation while in ethanol-rich and n-propanol-rich mixtures the solubility parameter is more responsible for the drug solvation. A nonlinear enthalpy-entropy relationships were observed in plots of enthalpy vs. Gibbs energy of solution. The plot of ∆solnH0 vs. ∆solnG0 show two different trends according to the slope obtained, the negative slope indicate that the driving mechanism is the entropy and positive slope indicate that the driving mechanism is the enthalpy. Otherwise, the linear enthalpy-entropy relationship was observed in a plot of enthalpy vs. entropy of solution too, in this case slope higher than one indicate that the driving mechanism is the enthalpy and the slope lower than one indicate that the driving mechanism is the entropy. On the other hand, the estimated solubility values obtained using semi empiric models pre- sent notorious deviations with respect to the experimental values. These results demonstrated that it is necessary to improve the theoretical strategies for estimating this property, and more over, they also demonstrated the great importance of the experimental determination of drugs solubility in those cosolvent mixtures useful in purification methods and dosage forms design.Doctorad

Mecanismo de acción y óptima selección de codisolventes en formas farmacéuticas

La solubilidad es una propiedad físico-química inherente de los principios activos. El reconocimiento de los factores que llevan a cabo el proceso de solubilidad constituyen una exigencia importante en el ámbito de la tecnología y desarrollo de sustancias farmacéuticas. El objetivo de esta memoria es la caracterización de la solubilidad de cuatro sustancias activas (alopurinol y probenecid, que se utilizan para el tratamiento de la hiperuricemia y sus complicaciones, y metamizol magnésico y el naproxeno sódico como analgésico y / o antipirético) en una batería de mezclas disolventes en las que se varia el porcentaje de mezcla de los disolventes, que cubren una amplia gama de polaridad (14-48MPa1 / 2), y a varias temperaturas (15-35 º C). La solubilidad experimental se determina en primer lugar, en concentraciones saturadas a varias temperaturas y diferentes mezclas de codisolventes, mediante técnicas espectrofotométricas. Los perfiles de solubilidad están representados por la solubilidad experimental, expresada en fracción molar, frente parámetro de solubilidad disolvente, el cuál representa la polaridad del disolvente en etanol-agua, acetato de etilo-etanol y hexano-acetato de etilo. El perfil de solubilidad puede estar relacionado con la polaridad de cada fármaco. Se pueden encontrar uno o dos máximos de solubilidad; dos picos son indicativos de efecto camaleónico, que se puede describir cuantitativamente en términos de formación de la cavidad y de interacciones específicas y no específicas, representada por el parámetro de solubilidad de Hildebrand y parámetros de solubilidad ácido-base.Por otra parte, el parámetro de solubilidad de los fármacos y otras características que pueden dar una idea del comportamiento soluble de un fármaco, son determinados y caracterizados para todas las sustancias de estudio.Los modelos de predicción de la solubilidad son una herramienta diseñada para ahorrar recursos económicos y logísticos para la estimación teórica de la solubilidad. Varios modelos matemáticos de predicción de solubilidad se prueban en este trabajo, lo que demuestra que la aplicación de los modelos de estimación de la solubilidad, constituyen una ventaja útil.Otro elemento que afecta el mecanismo que gestiona la solubilidad de los solutos, son los factores termodinámicos. Las magnitudes termodinámicas se estudian ampliamente en este trabajo. Entalpía, entropía y energía libre de Gibbs en la disolución, mezcla o proceso de transferencia serán determinados.Un análisis de la compensación entalpía-entropía confirma la existencia de dos mecanismos diferentes implicados en la solubilidad. Se han encontrado relaciones entalpía- energías de disolución no lineales para el alopurinol y el probenecid, cambiando la pendiente de positivo a negativo en determinadas proporciones. El análisis de compensación para estos medicamentos muestra que en las regiones polares, la estructura de la propia mezcla determina la solubilidad, mientras que a concentraciones de codisolvente mayores, las interacciones soluto-disolvente son el mecanismo dominante dependiendo de la naturaleza del soluto. Los dos derivados salinos muestran un comportamiento lineal en la relación calor de disolución frente a la composición de la mezcla, donde se observa un máximo definido. Estos medicamentos tienen un único máximo de solubilidad, en donde el pico se localiza en la región de agua-etanol. Una compensación entalpía-entropía lineal se observó en las dos fracciones de mezcla, sin embargo, un cambio en la pendiente sugieren que el cambio de solubilidad es determinado por un solo mecanismo: entalpía

Mecanismo de acción y óptima selección de codisolventes en formas farmacéuticas

La solubilidad es una propiedad físico-química inherente de los principios activos. El reconocimiento de los factores que llevan a cabo el proceso de solubilidad constituyen una exigencia importante en el ámbito de la tecnología y desarrollo de sustancias farmacéuticas. El objetivo de esta memoria es la caracterización de la solubilidad de cuatro sustancias activas (alopurinol y probenecid, que se utilizan para el tratamiento de la hiperuricemia y sus complicaciones, y metamizol magnésico y el naproxeno sódico como analgésico y / o antipirético) en una batería de mezclas disolventes en las que se varia el porcentaje de mezcla de los disolventes, que cubren una amplia gama de polaridad (14-48MPa1 / 2), y a varias temperaturas (15-35 º C). La solubilidad experimental se determina en primer lugar, en concentraciones saturadas a varias temperaturas y diferentes mezclas de codisolventes, mediante técnicas espectrofotométricas. Los perfiles de solubilidad están representados por la solubilidad experimental, expresada en fracción molar, frente parámetro de solubilidad disolvente, el cuál representa la polaridad del disolvente en etanol-agua, acetato de etilo-etanol y hexano-acetato de etilo. El perfil de solubilidad puede estar relacionado con la polaridad de cada fármaco. Se pueden encontrar uno o dos máximos de solubilidad; dos picos son indicativos de efecto camaleónico, que se puede describir cuantitativamente en términos de formación de la cavidad y de interacciones específicas y no específicas, representada por el parámetro de solubilidad de Hildebrand y parámetros de solubilidad ácido-base.Por otra parte, el parámetro de solubilidad de los fármacos y otras características que pueden dar una idea del comportamiento soluble de un fármaco, son determinados y caracterizados para todas las sustancias de estudio.Los modelos de predicción de la solubilidad son una herramienta diseñada para ahorrar recursos económicos y logísticos para la estimación teórica de la solubilidad. Varios modelos matemáticos de predicción de solubilidad se prueban en este trabajo, lo que demuestra que la aplicación de los modelos de estimación de la solubilidad, constituyen una ventaja útil.Otro elemento que afecta el mecanismo que gestiona la solubilidad de los solutos, son los factores termodinámicos. Las magnitudes termodinámicas se estudian ampliamente en este trabajo. Entalpía, entropía y energía libre de Gibbs en la disolución, mezcla o proceso de transferencia serán determinados.Un análisis de la compensación entalpía-entropía confirma la existencia de dos mecanismos diferentes implicados en la solubilidad. Se han encontrado relaciones entalpía- energías de disolución no lineales para el alopurinol y el probenecid, cambiando la pendiente de positivo a negativo en determinadas proporciones. El análisis de compensación para estos medicamentos muestra que en las regiones polares, la estructura de la propia mezcla determina la solubilidad, mientras que a concentraciones de codisolvente mayores, las interacciones soluto-disolvente son el mecanismo dominante dependiendo de la naturaleza del soluto. Los dos derivados salinos muestran un comportamiento lineal en la relación calor de disolución frente a la composición de la mezcla, donde se observa un máximo definido. Estos medicamentos tienen un único máximo de solubilidad, en donde el pico se localiza en la región de agua-etanol. Una compensación entalpía-entropía lineal se observó en las dos fracciones de mezcla, sin embargo, un cambio en la pendiente sugieren que el cambio de solubilidad es determinado por un solo mecanismo: entalpía

Activity of complex multifunctional organic compounds in common solvents.

Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2009.The models used in the prediction of activity coefficients are important tools for designing major unit operations (distillation columns, liquid-liquid extractors etc). In the petrochemical and chemical industry, well established methods such as UNIFAC and ASOG are routinely employed for the prediction of the activity coefficient. These methods are, however, reliant on binary group interaction parameters which need to be fitted to reliable experimental data. It is for this reason that these methods are often not applicable to systems which involve complex molecules. In these systems, typically solid-liquid equilibria are of interest where the solid is some pharmaceutical product or intermediate or a molecule of similar complexity (the term complex here refers to situations where molecules contain several functional groups which are either polar, hydrogen bonding, or lead to mesomeric structures in equilibrium). In many applications, due to economic and environmental considerations, a list of no more than 20 solvents is usually considered. It is for this reason that the objective of this work is to develop a method for predicting the activity coefficient of complex multifunctional compounds in some common solvents. The segment activity coefficient approaches proposed by Hansen, MOSCED and the NRTL-SAC models show that it should be possible to “interpolate” between solvents if suitable reference solvents are available (e.g. non-polar, polar and hydrogen bonding). Therefore it is useful to classify the different solvents into suitable categories inside which analogous behaviour should be observed. To accomplish this, a significant amount of data needs to be collected for the common solvents. Data with water as a solvent was freely available and multiple sources were found with suitable data. Both infinite dilution activity coefficient (y∞) and SLE (Solid-Liquid Equilibrium) data were used for model development. The y∞ data were taken from the DDB (Dortmund Data Bank) and SLE data were taken from Beilstein, Chemspider and DDB. The limiting factor for the usage of SLE data was the availability of fusion data (heat of fusion and melting temperature) for the solute. Since y∞ in water is essentially a pure component property it was modelled as such, using the experience gained previously by this group. The overall RMD percentage (in ln y∞) for the training set was 7.3 % for 630 compounds. For the test set the RMD (in ln y∞) was 9.1 % for 25 fairly complex compounds. Typically the temperature dependence of y∞ data is ignored when considering model development such as this. Nevertheless, the temperature dependence was investigated and it was found that a very simple general correlation showed moderate accuracy when predicting the temperature dependence of compounds with low solubility. Data for solvents other than water were very scarce, with insufficient data to develop a model with reasonable accuracy. A novel method is proposed for the alkane solvents, which allows the values in any alkane solvent to be converted to a value in the solvent hexane. The method relies on a first principles application of the solution of groups concept. Quite unexpectedly throughout the course of developing the method, several shortfalls were uncovered in the combinatorial expressions used by UNIFAC and mod. UNIFAC. These shortfalls were empirically accounted for and a new expression for infinite dilution activity coefficient is proposed. This expression is however not readily applicable to mixtures and therefore requires some further attention. The method allows for the extension of the data available in hexane (chosen since it is a common solvent for complex compounds). In the same way as the y∞ data in water, the y∞ data in hexane were modelled as a pure component property. The overall RMD percentage (in ln y∞) for the training set was 21.4 % for 181 compounds. For the test set the RMD (in ln y∞) was 11.7 % for 14 fairly complex compounds. The great advantage of both these methods is that, since they are treated as pure component properties, the number of model parameters grows linearly with the number of groups, unlike with mixture models (UNIFAC, ASOG, etc.) where it grows quadratically. For both the water and the hexane method the predictions of the method developed in this work were compared to the predictions of UNIFAC, mod. UNIFAC, COSMO-RS(OL) and COSMO-SAC. Since water and hexane are not the only solvents of practical interest, a method was developed to interpolate the alcohol behaviour based on the water and hexane behaviour. The ability to predict the infinite dilution activity coefficient in various solvents allowed for the prediction of various other properties, viz. air-water partition coefficient, octanol-water partition coefficient, and water-alcohol cosolvent mixtures. In most cases the predictions of these properties were good, even for the fairly complex compounds tested

The calculation of physicochemical descriptors and their application in predicting properties of drugs and other compounds.

The work presented may be divided into two main sections: The first section focuses on the important aspect of compound descriptor determination. The method by which descriptors are obtained indirectly through compound solubility in organic solvents and direct water-solvent partition measurements is illustrated by example for drug compounds. This approach is extended through the derivation of gas-water and water-solvent partition equations for the n-alcohols which in the future will be available for use in descriptor determination. Importantly, the equation coefficients are also interpreted to deduce various physicochemical properties of the homologous series of alcohols. An alternative method to assign descriptors is probed through reversed-phase HPLC. Measurements are recorded for a series of solutes on several bonded phases and multivariate analysis is used to investigate the interrelationship between columns in an effort to isolate the most suitable phases. The second section is concerned with application of the Abraham General Solvation Equation to examine processes of special interest in drug design; aqueous solubility and intestinal absorption. An algorithm to predict water solubility is obtained containing an additional cross-term which is found to compensate at least partly for a melting point correction term. The amended equation is shown to be comparable in accuracy to commercially available packages for a test set of 268 structurally diverse compounds. Of further importance in drug delivery is the process of intestinal absorption. An extensive literature search provides evaluated absorption data for a large set of drug compounds and forms a strong basis for subsequent QSAR analysis. Intestinal absorption is found to be comparable in humans and rat, and predominantly dependent on the hydrogen-bonding capability of the drug. The mechanism of absorption is considered through transformation of the percent absorption data to an overall rate constant

Thermochemical Study of Crystalline Solutes Dissolved in Ternary Hydrogen-Bonding Solvent Mixtures

The purpose of this dissertation is to investigate the thermochemical properties of nonelectrolyte solutes dissolved in ternary solvent mixtures, and to develop mathematical expressions for predicting and describing behavior in the solvent mixtures. Forty-five ternary solvent systems were studied containing an ether (Methyl tert-butyl ether, Dibutyl ether, or 1,4-Dioxane), an alcohol (1-Propanol, 2-Propanol, 1-Butanol, 2-Butanol, or 2-Methyl-1-propanol), and an alkane (Cyclohexane, Heptane, or 2,2,4-Trimethylpentane) cosolvents. The Combined NIBS (Nearly Ideal Binary Solvent)/Redlich-Kister equation was used to assess the experimental data. The average percent deviation between predicted and observed values was less than ± 2 per cent error, documenting that this model provides a fairly accurate description of the observed solubility behavior. In addition, Mobile Order theory, the Kretschmer-Wiebe model, and the Mecke-Kempter model were extended to ternary solvent mixtures containing an alcohol (or an alkoxyalcohol) and alkane cosolvents. Expressions derived from Mobile Order theory predicted the experimental mole fraction solubility of anthracene in ternary alcohol + alkane + alkane mixtures to within ± 5.8%, in ternary alcohol + alcohol + alkane mixtures to within ± 4.0%, and in ternary alcohol + alcohol + alcohol mixtures to within ± 3.6%. In comparison, expressions derived from the Kretschmer-Wiebe model and the Mecke-Kempter model predicted the anthracene solubility in ternary alcohol + alkane + alkane mixtures to within ± 8.2% and ± 8.8%, respectively. The Kretschmer-Wiebe model and the Mecke-Kempter model could not be extended easily to systems containing two or more alcohol cosolvents

Pharmaceutical Cocrystal Eutectic Analysis: Study of Thermodynamic Stability, Solubility, and Phase Behavior

Cocrystals are an emerging solid-state form to change physicochemical and biopharmaceutical drug properties. This dissertation focuses on the thermodynamic stability and solubility of pharmaceutical cocrystals. Specifically, the objectives are to: (i) develop methods to measure the thermodynamic solubility of metastable cocrystals, (ii) provide models that describe the equilibrium phase behavior of cocrystals based on component and cocrystal properties, (iii) explain the effect of temperature on cocrystal thermodynamic stability, (iv) estimate solubility and stability for different solvents based on component activity coefficients and measured cocrystal solubility in one solvent, and (v) identify mechanisms by which hygroscopic additives affect the stability of mixtures of solid cocrystal components. Cocrystal solubilities were calculated from eutectic concentration measurements where solution is in equilibrium with solid drug and cocrystal. Cocrystal solubility was directly proportional to coformer eutectic concentration and to the solubility of cocrystal components for carbamazepine, caffeine, and theophylline cocrystals. Cocrystal eutectic constants (Keu), the ratio of solution activities of cocrystal components at the eutectic, are fundamental indicators of phase behavior and are a function of the cocrystal to drug solubility ratio (α) in pure solvent. More than forty eutectic constants are presented that demonstrate Keu dependence on i) solvent, ii) complexation, and iii) ionization, as does the solubility of cocrystals. Applications of these findings to the discovery and phase stability of carbamazepine-sarcosine anhydride cocrystals are presented. A solution-mediated mechanism of cocrystal formation is shown for cocrystal components mixed with hygroscopic additives that sorbed moisture. More cocrystal formation occurred for additives that lowered the Keu. Keu temperature dependence is explained by thermodynamic models based on cocrystal and component enthalpies of solution, which are solvent specific. The Keu and α values of carbamazepine-nicotinamide in water decreased with temperature, but for several organic solvents Keu was temperature independent (4-47˚C). Cocrystal solubility and stability was also shown to depend on the component activity coefficients, which were estimated using the component solubilities. The models developed based on component and cocrystal properties combined with methods to estimate cocrystal solubilities from eutectic concentrations provide a useful guide for cocrystal design, synthesis, and selection.Ph.D.Pharmaceutical SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/76018/1/davemail_1.pd

Physicochemical studies of some compounds

Not availabl

Bioactivity of Substituted Copper Pyrithione Complexes

Over the last century, metal complexes have been popularised in therapeutic drug design. Copper complexes have been particularly interesting due to their high stability constants and unique redox chemistry. Simple copper salts, such as CuCl2 have little cytotoxicity, but ligands have been designed that lead to therapeutically activity copper complexes. The copper complex of pyrithione, a well-known ionophore, has recently been identified as a potent antibacterial and anticancer agent. Copper pyrithione has been shown to inactivate β-lactamase enzymes (such as NDM-1), a key enzyme in the mechanism of antibiotic resistance of multidrug-resistant bacteria. Antibiotic resistance being a great threat to human health around the world, copper pyrithione has potential in the development of new drug molecules. Key issues of this complex remain, including its low bacterial selectivity and poor aqueous solubility. This thesis focuses on structural modifications of the copper pyrithione complex with an aim to improve aqueous solubility, as well as optimise bioactivity as antibacterial and anticancer agents. The synthesis and characterisation are described of series of novel copper pyrithione complexes with functional groups variation in the pyrithione ligand. Derivatives include electron donating and electron withdrawing groups, aromatic substituents, and polyethylene glycol (PEG) chains. These complexes are subjected to physiochemical property analysis. Binding constant (log K), lipophilicity (log P) and solubility of some selected complexes are determined, and structure-property correlations are established in some cases. PEG-substituted complexes are highly soluble in water and possess a good balance of solubility and lipophilicity. All complexes are screened against various multidrug-resistant bacterial species and the majority show good activity against Gram-positive bacterial species. One complex, [Cu(5-Me-PT)2], shows good selectivity towards bacterial cells over healthy mammalian Vero cells, which augurs well for their use as novel antibiotics. Antibiotic synergy studies of copper pyrithione complexes alongside β-lactam antibiotics are performed, which shows that copper pyrithione complexes can act in combination with known antibiotics (meropenem and ertapenem) to overcome resistance in β-lactam resistant bacterial strains. Furthermore, cytotoxicity studies are performed with pancreatic carcinoma, bone osteosarcoma and healthy retinal epithelial cells, leading to structure-activity relationships to be proposed. Many novel complexes show high anticancer activity, with one complex [Cu(3-OMe-PT)2] showing particularly notable activity, with nanomolar inhibitory concentration (IC50 value) against pancreatic cancer. In next part of this project, the synthesis and characterisation of a fluorescent tagged copper pyrithione derivative using an alkyne-azide ‘click’ reaction is described. Photoluminescence properties of this complex are determined utilising UV/Vis absorption and fluorescence spectroscopies. Copper conjugation quenches the fluorescence emission of the fluorescent tag to some extent. Fluorescence microscopy study reveals this complex can enter and be visible inside live cells, showing specific localisation around the endoplasmic reticulum. Finally, some non-pyrithione copper complexes are described with an oxygen analogue of pyrithione showing particularly good bioactivity against both bacteria and cancer cells

Supercritical fluid extraction and analysis of indigenous medicinal plants for uterotonic activity.

Thesis (Ph.D.)-University of Natal, Durban, 1997.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