THE PHARMACEUTICAL EVALUATION OF I. GABONENSIS

THE PHARMACEUTICAL EVALUATION OF I. GABONENSIS

Abstract:

This study deals with the pharmacognostic aspects of the leaves, fruits and seeds of Irvingia gabonensls (O’Rorke) Baill, with special reference to its seed fat content. I. gabonensls is a forest tree up to 25 meters high and 2 meters in girth. The plant is widelydistributed in Nigeria especially in the Eastern and Western regions of the country, where the kernels are an important source of food. They are eaten in various parts of West Africa. The plant has two varieties, namely gabonensls with sweet edible fruits and excels a with bitter inedible fruits. Detailed macroscopical, microscopical and phytochemical studies were carried out on the two varieties of the plant and pharmacognostic parameters were established for the identification of the two varieties. Also, some pharmacopoeial standards have been recommended for I. gabonensls leaves and kernels. The composition of the fatty acid in the seed fat was determined by different chromatographic techniques including thin layer chromatography (TLC), gas chromatography/mass spectrometry (GC/MS) and high resolution gas chromatography (HRGC). TLC of the hydrolysed seed fat on silica gel plates impregnated with AgNO3 revealed the presence of viii lauric, myristic, stearic and oleic fatty acids. For GC/MS analysis, the seed fat was first hydrolysed and the free fatty acids (FFE) were derivatized to methyl esters (FAME) before injecting onto a carbowax column. Identification was made by comparing the retention time and mass spectra of the FAME with computerized reference data. The fatty acids identified were capric, lauric, myristic, palmitic, stearic, oleic and linolic acids. The so called “Dika Fat” was indeed found to be a mixture of fat and wax. The “fat” was only partially hydrolysed with aqueous KOH to afford glycerol and the fatty acids. On the other hand, alcoholic KOH hydrolysed the “fat” completely to afford glycerol and an alcohol which was immiscible with water. The percentage composition of the fatty acids in the seed fat was determined by the HRGC of the FAME on a GC equiped with fused silica column. It was found that myristic acid (52.3190 and lauric acid (36.9250 were the principal saturated acids in I. gabonensis var. excels a seed fat. The unsaturated acids were present In very low concentration. Similar results were ontained for I.gabonensis var. gabonensis. The seed fat was evaluated as a possible base for ointment and suppository dosage forms. Wool fat and castor oil were mixed separately with the seed fat in different proportions to produce semisolid preparations of such consistency and composition that ix can be applied on the skin by inunction. The seed fat mixed with either 20% wool fat or with 30% castor oil produced two suitable ointment bases with the desired properties. The rate of release of drugs from these bases was studied using the water soluble resorcinol and the less water soluble s a l i c y l i c acid. The results indicate that the rate of release of resorcinol was lower than the r a t e of release of s a l i c y l i c acid while the ointment bases formulated with the seed fat and wool fat released more drugs than those formulated with the seed fat and castor o i l. A suppository base consisting of wool fat (10%) and the seed fat (90%) was formulated and chloroquine suppositories prepared by incorporating chloroquine phosphate into these bases was further evaluated. The physiological studies on adult rats fed with this formulated seed fat for four weeks, showed significant increase in the serum cholesterol, triglyceride and t o t a l l i p i d levels, indicating that pharmaceutical applications of the seed fat should be regulated to avoid i t s possible side effects. This work highlights the economic potentials of the plant I. gabonensis and indicates the p o s s i b i l i ty of exploiting i t s fat content in addition to the kernel mucilage as a source of raw materials for the pharmaceutical industry.

THE PHARMACEUTICAL EVALUATION OF I. GABONENSIS