Limonin

The competition among drugs for binding to plasma proteins is regarded as a pharmacokinetic drug interaction. Competition between antitumor agents and other drugs for plasma protein binding can alter the free concentration of the drug, potentially impacting its efficacy and increasing the risk of toxic side effects. Through a range of spectroscopic techniques, this study examined the interaction between limonin and human serum albumin (HSA) in the context of berberine (Ber) and curcumin (Cur) under physiological conditions to clarify the binding mechanisms of binary and ternary systems at the molecular level. As demonstrated by fluorescence quenching experiments, Static quenching was identified as the mechanism of interaction between HSA and limonin. The results of site competition experiments indicated that the binding site between limonin and HSA was site I, a result further supported by molecular docking simulations. Through the use of thermodynamic data calculations, it was determined that limonin forms a stable complex with HSA by establishing hydrogen bonds and van der Waals forces. Circular dichroism (CD) spectroscopy, three-dimensional (3D) fluorescence spectroscopy, and synchronous fluorescence spectroscopy (SFS) employed to validate the notion that limonin perturbed the microenvironment of amino acids and induced conformational changes in HSA. What's more, the presence of Ber or Cur was found to have further modified the alterations observed in the interaction between the original HSA-limonin binary system. In vitro cellular experiments showed that interaction with HSA reduced the antitumor activity of limonin. In contrast, adding Ber or Cur increased the inhibition rate of tumor cells. The coexistence of both Ber and Cur significantly diminished limonin's binding affinity to HSA. The current investigation enhances comprehension regarding the binding characteristics and interaction mechanisms involving limonin, Ber, Cur, and HSA. It explores the potential of HSA as a versatile drug carrier and furnishes theoretical underpinnings for co-administrative strategies.

Recent discoveries have illustrated that Lin28A is an oncogene in various cancers, particularly acute myeloid leukemia (AML). The upregulation of Lin28A can actively contribute to tumorigenesis and migration processes in multiple organs. Hence, the inhibition of Lin28A can be achieved by applying phytochemical herbals and targeting Lin28A protein using a computer-aided drug design (CAAD) approach.

In this study, we comprehensively applied several bioinformatics tools, including gene ontologies, gene enrichment analysis, and protein-protein interactions (PPI), to determine the biological pathways, functional gene ontology, and biological pathway. Furthermore, we investigated a list of phytochemical herbs as a candidate drug by applying a computation technique involving molecular docking, density functional theory (DFT), molecular dynamics simulation (MDs), and pharmacokinetic and physiochemical properties by applying the SwissADME, pkCSM, and Molsoft LLC web-servers.

The Lin28A gene is related to two significant enrichment pathways, including proteoglycans in cancer and the pluripotency of stem cells through interactions with different genes such as MAPK12, MYC, MTOR, and PIK3CA. Interestingly, limonin, 18β Glycyrrhetic Acid, and baicalein have the highest binding energy scores of -8.4, -8.2, and -7.3 kcal/mol, respectively. The DFT study revealed that baicalein has a higher reactivity than limonin and 18β-Glycyrrhetic due to a small energy gap between LUMO and HUMO. Molecular dynamics simulation exhibited that baicalein complex with Lin28A protein is more stable than other complexes during simulation time due to low fluctuation with simulation periods as compared with other complexes, which indicated that baicalein was more fitting to docking and combining in the protein cave because of the largest number of H-bonds available for the docking simulation process. Furthermore, the drug-likeness and ADMET profiles revealed the activity of limonin, baicalein, and 18β-glycyrrhizic Acid, which possess significant inhibiting Lin28A proteins.

This study elucidated that baicalein, 18β-glycyrrhizic, and limonin may be applied as potential candidates for targeting Lin28A as an active oncogene for acute myeloid leukemia.