Nasal Administration of a Nanoemulsion Based on Methyl Ferulate and Eugenol Encapsulated in Chitosan Oleate: Uptake Studies in the Central Nervous System

Background/Objectives: The phytochemicals ferulic acid (Fer) and eugenol display neuroprotective effects for their anti-oxidative properties; moreover, eugenol can induce dopamine (DA) release from dopaminergic neuronal cells. However, poor bioavailability and/or fast elimination rate limit their clinical benefits. We therefore propose a new nasal formulation based on a nanoemulsion (NE) for the jointed brain-targeting of eugenol and methyl ferulate (Fer-Me, i.e., a Fer-lipidized derivative maintaining the parent compound anti-oxidative properties). NE was obtained using chitosan oleate, a surfactant combining mucoadhesive and absorption-enhancing properties with stabilizing effects on the dispersion of eugenol, used as a Fer-Me vehicle. Methods: The nasal formulation was obtained by spontaneous emulsification processes; cell viability and uptake studies were performed on an in vitro model of respiratory mucosa (RPMI 2650 cells). After intravenous and nasal administrations, the pharmacokinetic profiles of eugenol and Fer-Me in rats’ bloodstreams and cerebrospinal fluid (CSF) were analyzed via HPLC-UV analysis. Results: The NE dispersed-phase mean diameter was 249.22 ± 32.78 nm; Fer-Me and eugenol loading in NE was about 1 and 2 mg/mL, respectively. NE increased the uptake of loaded compounds by mucosal cells. Following intravenous administration, the Fer-Me plasma half-life was 10.08 ± 0.37 min, and a negligible ability of the compound to permeate in the CSF, compared to eugenol, was observed. NE nasal administration allowed us to sensibly increase the Fer-Me brain-targeting and prolong the eugenol permanence in the CSF. Conclusions: This nasal formulation appears promising to overcome Fer and eugenol pharmacokinetic issues. The possible translational relevance of the present findings is discussed.