Aflatoxin B₁ Induced Structural and Conformational Changes in Bovine Serum Albumin: A Multispectroscopic and Circular Dichroism-Based Study

Abstract

Aflatoxin B 1 (AFB 1 ) is a mutagen that has been categorized as a group 1 human carcinogen by the International Agency for Research on Cancer. It is produced as a secondary metabolite by soil fungi Aspergillus flavus and Aspergillus parasiticus. Here, in this study, the effect of AFB 1 on the structure and conformation of bovine serum albumin (BSA) using multispectroscopic tools like fluorescence spectroscopy, ultraviolet−visible absorption spectroscopy, and circular dichroism spectropolarimetry has been ascertained. Ultraviolet absorption spectroscopy revealed hyperchromicity in the absorption spectra of BSA in the presence of AFB 1 . The binding constant was calculated in the range of 10 4 M −1 , by fluorescence spectroscopy suggesting moderate binding of the toxin to BSA. The study also confirms the static nature of fluorescence quenching. The stoichiometry of binding sites was found to be unity. The competing capability of warfarin for AFB 1 was higher than ibuprofen as calculated from site marker displacement assay. Forster resonance energy transfer confirmed the high efficiency of energy transfer from BSA to AFB 1 . Circular dichroism spectropolarimetry showed a decrease in the α-helix in BSA in the presence of AFB 1 . The melting temperature of BSA underwent an increment in the presence of a mycotoxin from 62.5 to 70.3 °C. Molecular docking confirmed the binding of AFB 1 to subdomain IIA in BSA. ■ HIGHLIGHTS• In this study, binding dynamics of AFB 1 with BSA were explored by UV absorption spectroscopy, fluorescence spectroscopy, and molecular docking.• Molecular docking analysis substantiated that Arg-217, Tyr-149, Arg-256, and Ala-260 residues stabilize the interacting complex via hydrogen bonding.

May phytophenolics alleviate aflatoxins-induced health challenges? A holistic insight on current landscape and future prospects

“…As discussed formerly, AFs displayed a potent binding affinity to human HSA (191) as well as BSA (193). PPs such as resveratrol could compete with AFs to bind to critical active sites of HSA by which showed an influential effect to decrease the bioavailability of AFB1 and displace the stability of AFB1-HSA complex (177).…”

“…Similarly, the results of spectroscopic and computational assays also determined that AFB1 and AFG1 also interacted with subdomain IB residues in HSA ( 192 ). AFB1 also displayed a similar binding affinity to interact with bovine serum albumin (BSA) binding site I with a binding constant of nearly 4.20 × 10 4 M −1 ( 193 ). These outcomes together demonstrated the precise interaction of AFs and HSA, leading to a better understanding of toxicokinetic properties of these mycotoxins.…”

“…Decreasing the affinity of HSA to AFs with chemical compounds sharing similar binding patterns with higher affinities in comparison to AFB1 might bring down the toxicity of this mycotoxin for the human body ( 193 ). Studies have shown that natural products such as PPs interfere with the interaction between AFB1 and HSA and reduce the transportation of AFs to delivery locations ( 177 , 194 ).…”

“…These findings are in agreement with previous outcomes demonstrated that exposure to AFs metabolites is associated with plasma micronutrient deficiencies ( 199 ). However, mycotoxin metabolites could bind to HSA ( 189 , 193 ); therefore, these toxins are easily transported to different parts of the human body and causing chronic health consequences ( 189 ). In the next section, we explain how metabolized AFs derivatives are accounting for prevalence of nCDs.…”

Investigating binding dynamics of trans resveratrol to HSA for an efficient displacement of aflatoxin B1 using spectroscopy and molecular simulation

“…Though, studies aiming at the fate of this hepato-carcinogen in the presence of serum albumin and vice versa are fewer. Recently few studies focused on the binding behavior of AFB 1 with BSA, HSA, and chicken egg albumin 16 – 18 , provided information about its binding constant, site of binding, and thermodynamic parameters. Still, these studies have gaps that need to be filled by an approach that could unload the mycotoxin from the precise binding location in serum albumin, leading to its biotransformation followed by its elimination from the body.…”