This study describes the isolation of bioactive compounds and their in vitro anticancer activities from Melia azedarach L leaves from Karanglor, Karangan, Karanganom Klaten, Central Java-Indonesia. Isolated and characterised were the phenolics, kaempferol 7-O-rutinoside 1 and 4-methoxyresorcinol 3, The anticancer activity of the crude methanol extract of M. azedarach against a number cell lines (LNCaP, MDA-MB-231, and MCF-7) was found to be moderate; kaempferol derivatives were notable for their antiproliferative activities. Computational analysis, including molecular docking simulations and molecular dynamic studies, were used to investigate the feasibility of radiolabelled versions of 1 and 3 as theranostic agents targeting tyrosine kinase-type cell surface receptor HER2 in cancer - the iodinated derivatives 2 and 4, respectively, were used in this investigation as surrogates. The corresponding radioiodinated 2 and 4 were found to have high binding affinities of 10.1 and 5.7 kcal/mol, respectively, and have a good stability on the receptor.