This dissertation consists of two parts, Part A and Part B. Part A describes the phytochemical investigations of Berberis jaeschkeana Schneid var. jaeschkeana and Berberis glaucocarpa Stapf (Berberidaceae). A total of twenty two compounds (111-132) were isolated from the two plant species. These include four new compounds namely; 10-hydroxy chondrofoline (111), 8,12,12a-trihydroxy-11,13a-berberin-dione (112) 10-methoxy chondrofoline (113) and docosyl-2-hydroxytetracosanoate (114) and eighteen new source compounds from these plant species. The new source compounds are: berberine (115), palmatine (116), columbamine (117), pseudoberberine (118), gallic acid (119), β-sitosterol (120), 8-hydroxy-7,8- dihydroberberine (121), docosanoic acid (122), methyl gallate (123), oxyacanthine (124), jatrorrhizine (125), 8-oxoberberine (126), β-sitosterol glucoside (127), 8-trichloromethyldihydroberberine (128), pseudopalmatine (129), syringic acid (130), syringaresinol (131) and stigmasterol (132).The structure of all the isolated compounds were determined by various spectroscopic techniques like 1 HNMR, 13 CNMR, HMBC, HSQC, NOESY, COSY, DEPT, EIMS, ESIMS and HRESIMS. The structures of the new source compounds were confirmed by comparing their spectral data with the literature. Part B deal with the biological activities of crude extracts, fractions and compounds. Most of the compounds and fractions were evaluated for their anti-microbial, anti- trypanosomal, anti-fungal and anti-diabetic properties. Anti-microbial properties of fractions and compounds were determined using Alamar blue TM 96-well plate and agar xiv well diffusion method. Anti-fungal properties were evaluated using the tube dilution method. The anti-diabetic properties of fraction and compounds were evaluated by Protein Tyrosine Phosphatase 1B (PTP1B) enzyme method. Berberine (115), 8-trichloromethyldihydroberberine (128), jatrorrhizine (125), columbamine (117), and syringaresinol (131) and the fractions from which these compounds were isolated showed good anti-microbial properties. Similarly berberine (115), berberine chloroform (128), 8- oxoberberine (126), 10-hydroxy chondrofoline (111), syringaresinol (131) and their fractions showed good anti-trypanosomal properties. Most of the isolated compounds and fractions were also tested for their anti-fungal and anti-diabetic properties but none of them displayed significant anti-fungal or anti-diabetic properties. Some of them were moderately active.