Assessment of the Comparative Interactions of Cuminaldehyde with Bovine Serum Albumin and Human Serum Albumin Through Spectroscopic and Molecular Docking Investigation

Cuminaldehyde, an oxidized aldehyde monoterpene, present in green cumin seeds (Cuminum cyminum Linn, Family-Apiaceae), is traditionally used for the treatment of abdominal colic, dyspepsia, diarrhea, and jaundice. Also, many studies have reported the antioxidant, antibacterial and antifungal effects of cuminaldehyde. Serum albumins are the major soluble and small molecule-binding proteins, present in abundance in the circulatory system of a wide variety of organisms. Studies on the interaction of bioactive molecules with bovine serum albumin (BSA) and human serum albumin (HSA) have attracted enormous interest due to its direct consequence on drug delivery, pharmacokinetics, pharmacodynamics, therapeutic efficacy and drug designing. Our present study is carried out to understand the mechanism of interaction of pharmaceutically important component of spices, cuminaldehyde with BSA and HSA. Fluorescence spectroscopic measurements confirmed that cuminaldehyde interacted with BSA and HSA and quenched its fluorescence intensity via static quenching mechanism. UV-Visible absorption studies and CD-spectroscopy showed the change in secondary conformation of BSA and HSA upon interaction with cuminaldehyde. CD-spectroscopy revealed that HSA is unfolded at lower concentration of cuminaldehyde compared to BSA. The location of binding site for cuminaldehyde in BSA and HSA was investigated by site probe displacement experiments and the results indicated that cuminaldehyde preferred to bind site-I, located in subdomain IIA of both BSA and HSA. Thermodynamic studies revealed that vander Waal's interaction and hydrogen bonding play a major role in cuminaldehyde-BSA system while hydrophobic interactions play vital role in cuminaldehyde-HSA system. The molecular dockings of cuminaldehyde with BSA/HSA further confirmed the formation of the stable BSA/HSA-cuminaldehyde complex and cuminaldehyde binds at site-I of HSA. On the other hand, docking study showed that cuminaldehyde interacts with some residues close to site-I of BSA. Both experimental and theoretical results showed that the Delta G0 values are comparable for both the proteins, which indicate almost equal stability of cuminaldehyde-BSA and cuminaldehyde-HSA complex.