Phytochemical and Some Bio-activity Studies of Teclea Trichocarpa, Tovomita Mangle, Aspilia Pluriseta, Tephrosia Hildebrandtii, and Milletia Thonningil

Abstract

This thesis describes a chemical and bio activity study of five tropical plant species, namely Teclea trichocarpa Eng., Tovomita mangle G. Mariz., Aspilia pluriseta Schweinf., Tephrosia hildebrandtii Vatke. and Milletia thonningii (Schumach & Thonn.) Bak. From the bark of T. trichocarpa (Rutaceae) has been isolated three 9-acridone alkaloids, melicopicine, tecleanthine I and 6-methoxy tecleanthine. Both melicopicine and tecleanthine exhibited mild antifeedant activity against the African Armyworm, Spodoptera exempta while all the three alkaloids showed antimicrobial activity against the fungus, Cladosporium cucumerinum and the bacterium Bacillus subtilis. A chemical study of the root extract of T. mangle (Guttiferae) led to the isolation of two new benzophenones, benzophenone A and B, both containing the unusual lavundalyl chain. Three kauranoid diterpenoids were isolated from the leaves of A. pluriseta (Compositae), a Kenyan folk-medicinal plant that is widely used for the cure of wounds. The antibacterial activity of these compounds against six gram-positive and gram-negative bacteria is reported. From the roots of the shrub T. hildebrandtii (Leguminosae) was isolated a new flavanonol acetate together with the flavone trans-anhydro-techrostachin. The flavanonol acetate exhibited mild antifeedant activity against the African armyworm. Chemical studies on the seeds of Ill M. thonningii (Leguminosae) led to the isolation of a new pyrano-isoflavone together with three known isoflavones and robustic acid. Structural elucidation of these compounds was performed on the basis of their spectroscopic data and in some cases by chemical transformations. Antifeedant activity tests against S. exempta were done using the leaf disc bioassay with Zea mays. The antifungal activity was determined by the Cladosporium spray bioassay while antibacterial activity was established by the paper-disc method. The range of compounds isolated indicate that there may be a vast reservoir of yet untapped bioactive natural products in tropical flora which may be useful as medicines and pesticides or which may serve as useful models for medicinal and pesticidal compounds.