Abstract: With the aim of obtaining more potent curcumin analogues as well as to study the promise of curcuma endophytes in biotransformation process, fungal transformation of curcumin using an endophytic fungus was investigated. Endopyhtic fungi, existing as non-pathogenic microbes in the tissues of plants, have a capacity to transform certain chemical substances into their more potential analogues. Previous study showed that an endophytic fungus with code CL-Bel-5F, isolated from the rhizome of Curcuma longa L., was able to transform curcumin (1) into its analogue, however, its chemical structure has not been established yet. The purpose of current study, therefore, was to obtain the chemical structure of curcumin analogue produced by endophytic-fungal transformation. The result showed that biotransformation using endophytic fungus CL-Bel-5F, was successfully able to transform curcumin (1) to hexahydrocurcumin (5-hydroxy-1,7-bis(4-hydroxy-3-metoxyphenyl)-hepta-3-one) (2), whose structure was established based upon extensive spectroscopical analyses particularly 1D and 2D-NMR studies.