Human exposure and stability of a novel Citrus flavanone-based nutraceutical: a multi-matrix analytical approach

Introduction: Citrus flavanone glycosides are widely investigated for their
potential health benefits, including antioxidant, anti-inflammatory, and
cardiometabolic effects; however, human exposure and metabolic fate are
often inferred from plasma measurements alone, despite limited systemic
absorption and extensive intestinal processing.
Methods: In this study, we performed an integrated, translational assessment of
human exposure to a novel Citrus flavanone-based nutraceutical formulation
(FlavonAid™), combining plasma, urinary, and fecal analyses with comprehensive
analytical characterization and stability evaluation. Six healthy volunteers
received a single oral dose (174 mg total flavanones), and flavanone-related
compounds were quantified in plasma, urine, and feces using validated
chromatographic methods.
Results: Accelerated stability testing demonstrated minimal degradation (<3.5%
over 6 months) and high reliability of the formulation. Plasma analysis revealed
low and intermittent systemic exposure, with concentrations frequently close to
analytical limits and no reproducible pharmacokinetic profiles. In contrast, urinary
and fecal analyses showed substantial recovery of flavanone-related compounds
within 24 h. Mass balance analysis indicated that approximately 39% of the
administered dose was recovered in urine and feces during the first 24 h,
mainly as hydrolyzed parent flavanone glycoside equivalents, while shared
low-molecular-weight phenolic metabolites accounted for a major fraction of
the excreted material.
Discussion: Overall, these findings demonstrate that human exposure to Citrus
flavanones is best described through a multi-matrix approach that captures
coordinated intestinal metabolism, partial systemic handling, and prolonged
elimination rather than relying solely on plasma data. This study establishes a
robust methodological framework for evaluating flavanone-based nutraceuticals
in humans and supports further investigation of formulations designed to achieve
sustained intestinal exposure with limited systemic availability.