Xylocarpus granatum J. König (Meliaceae), commonly known as ‘dhundul’, is a Bangladeshi mangrove tree, and well distributed in a number of other countries of south‐east Asia, Australia and east Africa. Traditionally, X. granatum has been used as an astringent and febrifuge, and also for the treatment of fever, malaria, thrush, cholera, dysentery and diarrhoea in many countries including Bangladesh. Two limonoids, gedunin and 1α ‐hydroxy‐1,2‐dihydrogedunin, the latter being new, have been isolated from the bark of Xylocarpus granatum by reversed‐phase preparative HPLC, and the structures were confirmed by spectroscopic means. The cytotoxic potential of gedunin has been evaluated by the Promega's CellTiter 96 non‐radioactive cell proliferation assay using the CaCo‐2 colon cancer cell line (IC50 = 16.83 µm ). A summary of the biological activities of gedunin reported to date is also presented.