Insights into cannabinoid-HSA interactions: spectroscopic analysis and molecular docking for binding site characterization.

Cannabinoids are increasingly recognized for their therapeutic potential, yet their pharmacokinetics remain poorly understood due to their high hydrophobicity and complex interactions with plasma proteins. Human serum albumin (HSA), the principal drug carrier in blood, critically influences the distribution, bioavailability, and efficacy of lipophilic compounds. In this study, we comprehensively investigated the binding interactions between HSA and six major cannabinoids (THC, CBD, CBC, CBG, THCV, and CBDV) using fluorescence spectroscopy, synchronous fluorescence scanning (SFS), circular dichroism (CD) spectroscopy, and molecular docking simulations. Fluorescence quenching analysis revealed a static quenching mechanism, supported by quenching rate constants (K_b) exceeding diffusion limits. Temperature-dependent studies and van't Hoff analysis indicated that the interactions were driven primarily by hydrophobic forces, as evidenced by positive entropy and enthalpy changes. CD spectral analysis showed that most cannabinoids induced minimal or stabilizing effects on HSA's α-helical structure, with the exception of CBDV and CBG, which caused more pronounced, concentration-dependent secondary structure changes. Molecular docking localized the binding sites predominantly within Sudlow's sites I, involving key hydrophobic residues such as Ile, Leu, Val and Ala. Together, these findings provide new molecular insights into the transport properties of cannabinoids and highlight the role of albumin in modulating their pharmacokinetic profiles, offering valuable guidance for therapeutic drug design and delivery strategies.