AbstractThe objectives of this study are to isolate and determine the chemical compounds from Alphonsea cylindrica bark and also to investigate their antibacterial activities. Samples were collected from Kechau Tui, Kuala Lipis, Pahang. The samples were oven dried, ground and serially extracted by maceration technique using hexane, dichloromethane and methanol. Acid base extraction was performed on the dichloromethane extract. Chemical compounds were isolated and purified by means of various chromatographic techniques. Their structures were elucidated with modern spectroscopic techniques including 1D and 2D NMR, MS, IR, UV as well as comparison with literature review. Antibacterial activity on crude extracts and pure compounds was completed using disc diffusion technique. The results of phytochemical study have led to the isolation of seven chemical compounds which were stigmasterol, kinabaline, muniranine, O-methylmoschatoline, lysicamine, atherospermidine and N-methylouregidione. Compound mu.....