Novel Synthetic PEGylated Conjugate of α-Lipoic Acid and Tempol Reduces Cell Death in a Neuronal PC12 Clonal Line Subjected to Ischemia

α-Lipoic acid (α-LA), a natural thiol antioxidant, and Tempol, a synthetic free radical scavenger, are known to confer neuroprotection following ischemic insults in both in vivo and in vitro models. The aim of this study was to synthesize and characterize a conjugate of α-LA and Tempol linked by polyethylene glycol (PEG) in order to generate a more efficacious neuroprotectant molecule. AD3 (α-Tempol ester-ω-lipo ester PEG) was synthesized, purified, and characterized by flash chromatography and reverse phase high pressure liquid chromatography and by ¹H nuclear magnetic resonance, infrared spectroscopy, and mass spectrometry. AD3 conferred neuroprotection in a PC12 pheochromocytoma cell line of dopaminergic origin, exposed to oxygen and glucose deprivation (OGD) insult measured by LDH release. AD3 exhibited EC₅₀ at 10 μM and showed a 2-3-fold higher efficacy compared to the precursor moieties, indicating an intrinsic potent neuroprotective activity. AD3 attenuated by 25% the intracellular redox potential, by 54% lipid peroxidation and prevented phosphorylation of ERK, JNK, and p38 by 57%, 22%, and 21%, respectively. Cumulatively, these findings indicate that AD3 is a novel conjugate that confers neuroprotection by attenuation of MAPK phosphorylation and by modulation of the redox potential of the cells.