Bioconversion of curcumin into calebin-A by the endophytic fungus Ovatospora brasiliensis EPE-10 MTCC 25236 associated with Curcuma caesia

Calebin-A is a curcuminoid compound reported to be present in Curcuma longa rhizome. The current study was aimed to isolate and characterize calebin-A from Curcuma caesia rhizome and its production through biotransformation approach using endophytic fungus. C. caesia rhizomes of different ages were subjected to analysis in order to investigate the age at which maximum calebin-A content is present. HP-TLC profiles, HPLC retention times and mass spectrometry detector confirmed the occurrence of calebin-A in C. caesia rhizomes of 12 to 14 months of age but not in rhizomes younger to 12 months. Furthermore, an endophytic fungus strain, EPE-10 that was isolated from the medicinal plant C. caesia was identified as Ovatospora brasiliensis based on morphological and molecular characteristics. This strain O. brasiliensis was deposited to the culture collected centre, MTCC Chandigarh, India under the Budapest treaty and was designated with the Accession Number MTCC 25236. Biotransformation process was carried out at 37 ± 0.5 °C with shaking for 7 days after addition of 0.01% w/v curcumin. Extraction of biotransformed products was done by following partition method and the extracts obtained were analyzed using HPTLC, HPLC and LCMS. The data of the study suggested that O. brasiliensis MTCC 25236 was found to convert curcumin to calebin-A in a time dependant manner with optimum conversion at 48 h. Furthermore, O. brasiliensis MTCC 25236 was found to be positive for the Baeyer–Villiger monooxygenase (BVMOs) enzyme activity which could possibly be the mechanism of this bioconversion. The results of this study for the first time indicated that the endophytic fungus identified as O. brasiliensis MTCC 25236 isolated from the C. caesia rhizome could be a possible source for naturally producing calebin-A.