This paper reports two studies on plant alkaloids. First, alkaloids from the bark of three Aspidosperma species (A. formosanum, A. campus-belus, A. desmanthum, Apocynaceae) were investigated. Hot continuous ethanol extraction, concentration, 2N acetic acid maceration, and standard fractionation yielded about 10% syrupy extract. Compounds isolated included olivatine, uleine, 3-epiuleine, 1,13-dihydro-13-hydroxyuleine, aspidocarpine, lichexanthone, phthalimide, and aspidoalbine. Structures were identified using spectral data (UV, IR, NMR, MS) and comparison with authentic samples. Uleine, present in large quantities, was explored for chemical transformations into antischistosomicidal drug analogues. Lichexanthone probably originated from lichen on the bark, while the source of phthalimide was problematic. Second, a new indolopyridoquinazoline alkaloid, euxylophoricine F (C₁₉H₁₅O₃N₃), was isolated from the bark of Euxylophora paraensis (Rutaceae) from the mother liquors of 1-hydroxyrutaecarpine crystallization. Its structure was determined by spectroscopic methods (UV, IR, NMR, MS) and confirmed by synthesis: condensation of 4-benzyloxy-5-methoxyanthranilic acid methyl ester with 1,2,3,4-tetrahydronorharman-1-one followed by hydrogenolysis. Methylation with MeI-K₂CO₃ and hydrogenolysis reactions converted it to known compounds, supporting the structure. Its co-occurrence with other alkaloids suggests it may be a biogenetic precursor.