Elucidating the Neuroprotective Mechanisms of Tetrahydrocurcumin: A Key Curcumin Metabolite

Abstract

Neurodegenerative disorders such as Alzheimer’s disease and Parkinson’s disease are characterized by progressive “specific” neuronal loss at an “explicit” anatomical site in the brain driven by oxidative stress, mitochondrial dysfunction, neuroinflammation, apoptosis, excitotoxicity, and neurotransmitter dysregulation. Although the natural biogenic “Curcumin” exhibits promising neuroprotective properties, its clinical translation has been limited by poor solubility, rapid metabolic degradation, instability, and low systemic bioavailability. The present study integrates comprehensive in-silico pharmacokinetic modeling with in vitro pharmacodynamic and pharmacogenomic analyses to evaluate Tetrahydrocurcumin (THC), a hydrogenated derivative and a natural bioactive of Curcumin, as a pharmacokinetically optimized and mechanistically robust neuroprotective nutraceutical. An integrated in-silico framework incorporating physicochemical profiling, ADME prediction, pharmacokinetic simulation, molecular docking, and MM/GBSA analysis demonstrated that hydrogenation refines the pharmacological profile of Curcumin. THC exhibited improved aqueous solubility, fewer structural liabilities, enhanced systemic exposure, and markedly more favorable thermodynamic binding free energies at monoamine-degrading enzymes (MAOA, MAOB, and COMT), while maintaining multi-target engagement across dopaminergic and cholinergic receptors. Pharmacokinetic simulations predicted significantly greater plasma exposure (Cmax and AUC) following oral dosing without increased clearance burden, supporting improved bioavailability rather than accumulation. The absence of predicted P-gp substrate liability and preserved blood–brain barrier permeability further supports its potential for central nervous system exposure. In hippocampal HT22 neurons subjected to endogenous neurotoxin, hydrogen peroxide–induced neurotoxicity, THC significantly exerted multifaceted neuroprotection by significantly reducing oxidative stress (ROS and lipid peroxidation; restoring glutathione content), enhanced mitochondrial bioenergetics (increased mitochondrial Complex-I activity); suppressing inflammation (decreased COX and ICE-1 activity); attenuating apoptosis (inhibiting caspase-3 and caspase-8 activation); and increasing cholinergic function through increased ChAT and decreased AChE activity. Pharmacogenomic profiling further revealed that THC remodels oxidative stress, apoptotic, inflammatory, mitochondrial, and cholinergic gene networks toward an adaptive and survival-supportive state. In dopaminergic N27 neurons, THC significantly attenuated oxidative damage, restored Complex-I activity, suppressed inflammatory and apoptotic signaling, the dopamine synthesizing enzyme activity (Tyrosine hydroxylase activity and Aromatic Amino Acid Decarboxylase activity) and inhibited the dopamine degrading enzymes activity (monoamine oxidase and catechol-O-methyl transferase) activity, suggesting stabilization of dopamine metabolism. Importantly, THC exerted significant neuroprotective effects at low concentrations, which fall below the concentration ranges commonly reported for Curcumin in in vitro studies, suggesting potential enhanced prophylactic and therapeutic efficacy. Collectively, these integrated computational, biochemical, and pharmacogenomic findings identify THC as a pharmacokinetically enhanced and pharmacodynamically multi-target neuroprotective natural bioactive that targets and protects converging molecular pathways implicated in Alzheimer’s disease and Parkinson’s disease-related cholinergic and dopaminergic neurodegeneration, supporting its prioritization for further translational investigation.