PHARMACOGNOSY EVALUATION AND TOXICITY STUDIES OF THREE CROTALARIA SPECIES (LEGUMINOSAE)

PHARMACOGNOSY EVALUATION AND TOXICITY STUDIES OF THREE CROTALARIA SPECIES (LEGUMINOSAE)

ABSTRACT

The pharmacognostic evaluation of three species of the genus Crotalaria in Zaria is reported with special reference to their pyrrolizidine alkaloid contents and toxicity. The three species are Crotalaria microcarpa, Benth.; Crotalaria naraqutensis. Hutch.; and Crotalaria retusa, L.. Detailed study of their macroscopical and icroscopica) features, physical constants, phytochemical and ethnomedical investigations in addition to toxicity studies were carried out on these species. Parameters for identification of these plants have been determined. Alkaloids were detected in the aerial parts of all the three species except the leaves of C. naraqutensis. This confirms the classical toxonomical relationship between the species. Total alkaloid was determined by titrimetric method to be 0.17% and 0.06% for the leaves of C. retusa and C. microcarpa respectively. For the aerial parts, it was found to be 0.31% for C. retusa, 0.08% for C. microcarpa and 0.06% for C. naraqutensis. Other phytochemical constituents detected in the three Crotalaria species were flavonoids, tannins, carbohydrates and reducing sugars. Both anthraquinones and cardiac glycosides were detected in C. microcarpa only, cyanogenetic glycosides were detected in C naragutensis, while monosaccharides were detected in C. retusa only. Calorimetric Mattocks tests revealed the presence of hepatotoxic pyrrolizidine alkaloid bases in the leaves and aerial parts of C. retusa only of the three species. This plant is therefore the only toxic species among the three investigated. The alkaloids of C. retusa were therefore tested for toxicity on rats and it proved to be toxic to all rats with marked microscopic lesions found principally in the liver, lungs, kidney and intestine. Toxicity pattern was typical of monocrotaline. The qualitative identification of these alkaloids by chromatography indicated that the toxic alkaloid, monocrotaline, was indeed present in C. retusa along with two other alkaloids. A total of four alkaloids were also detected in C microcarpa and two in C naraqutensis aeriel parts. Extractive values of the Crotalaria species showed considerable differences especially for C. microcarpa while C. retusa and C. naraqutensis appear to be closely related. Alcohol soluble extractive value, acid insoluble ash, ash value and moisture content for C.microcarpa were found to be 15, 15, 20 and 5.6 respectively. While for C naraqutensis were determined to be 17.5, 7.5, 2.5 and 3. Values for C. retusa were 14, 12.5, 2 and 2.2. Ethnomedical investigations of Crotalaria species was carried out in Zaria to determine available species, those utilised in ethnomedicine and for fodder and their recipes. Questionnaires were administered to herbalists, herdsmen, veterinary and medical doctors. The exercise revealed a general lack of awareness of the general toxicity of these species among the populace. Crotalaria poisoning was also found to occur in livestock. Suggestions are therefore presented for prevention. The study has also highlighted the importance of evaluating all Crotalaria species in order to distinguish toxic and non-toxic species of this genus and recommendations for further investigations have been made. Crotalaria species are indeed important species with significant pharmaceutical, medical, agricultural and economic implications.

PHARMACOGNOSY EVALUATION AND TOXICITY STUDIES OF THREE CROTALARIA SPECIES (LEGUMINOSAE)