The chemical compositions of non volatile oil extracts from two Annoneceous plant species Monanthotaxis discolor and an undescribed Uvariodendron species which are endemic to Eastern Arc Mountains, Tanzania were determined by GC-MS. The biological activities of extracts and fractionated samples were also determined. Both methanol and dichloromethane extracts of the root bark of M. discolor showed mild antimicrobial activity and had positive brine shrimp test (BST). The BST test for dichloromethane extract of M. discolor root bark were LC50 41.794 µg/ml and that of methanol extract showed LC50 13.560 µg/ml. The petroleum ether and dichloromethane extracts of root bark of Uvariodendron species showed cytotoxicity of LC50 33.06 µg/ml and LC50 35.35 µg/ml, respectively. Twelve major constituents were identified from the dichloromethane extract of M. discolor root bark of which the following compounds were in high composition; α- cadinol (42.85%), (-)-alloaromadendrene (11.7%) aristolone (10.57 %), γ-cadinene (8.72%), δ- cadinene (3.44%) and cubenene (2.28%). The Second fraction of the third repeated column chromatography from the VLC fraction of dichloromethane extract and the first fraction of the VLC of methanol extract root bark revealed, among others 23 components of which the most abundant were; (-)-alloaromadendrene (15.1%), T-cadinol (8.08%), chamigren (5.3%) and γ- Cadinene (5.1%). Other components were also identified from other methanol fractions; (+)- aromadendrene, (18.2%), (-)-alloaromadendrene (12.8%), 4,9-muurodiene (5.3%), T-cadinol (83%), ς-himachelene (0.63%) and ledol (0.3%). The ethanol:dichloromethane (1:1) extract of the leaves of M. discolor showed four different components from those identified from root bark extracts among which heptacosane and tributylamine had percentage composition of (3.42%) and (0.34%),.respectively. The petroleum ether extract of the root bark of the undescribed Uvariodendron species revealed seven components of which the most abundant were methyl eugenol (38.7%) and elemicin (18.2%). For the ethanol extract of stem bark oil mixtures the most abundant components were δ-cadinol (0.25%), methyl eugenol (0.12%), isoelemecene (0.04%), and diisooctyphthalate (0.02%).