A comparison of binding interaction of angelicin and psoralen to bromelain a cysteine protease: Steady-state fluorescence, circular dichroism and molecular docking study

Abstract

Furocoumarins are photo-active arising in several medicinal plants when they are subjected to stress devising varied medicinal applications. Angelicin and psoralen are the two main active components of Psoralea corylifolia L., an herbal-medicinal plant used from early times to treat numerous skin-related disorders. It is extensively dispersed in the therapeutics in Indian and Chinese herbal mode treatment. Here we synthesized two isomeric furocoumarins angelicin and psoralen and investigated their interaction with a cysteine protease proteolytic enzyme bromelain, using different spectroscopic techniques like steady state fluorescence and circular dichroism to understand the binding affinity of the two furocoumarins with bromelain. Bromelain is a well-known phytotherapeutic ingredient displaying widespread medicinal applications. The binding constants and the number of binding sites for the interactions of angelicin and psoralen with bromelain were evaluated using the steady state fluorescence data at 298 K. An in-silico investigation was executed by docking the two isomeric furocoumarins angelicin and psoralen with bromelain which revealed that both bind with the same energy but at different sites, which also alters a little more in the case of psoralen than angelicin the secondary structure of bromelain as evidenced in Circular dichroism spectra. DFT study revealed the stability of both moieties. In conclusion, this study shed light on the effective application of bromelain complexed with angelicin and psoralen, for developing functional foods and also can be considered an effective carrier for angelicin and psoralen.