High-dose ionizing radiation induces severe multi-organ injury, yet no broadly effective, orally available countermeasure has been validated. Here we describe a fully oral, multi-component formulation comprising bioavailable polyphenol derivatives (pterostilbene cocrystals and silybin-phosphatidylcholine), the NAD⁺ precursor nicotinamide riboside, and captopril, an angiotensin-converting enzyme inhibitor with established radiomitigative activity that synergizes with the polyphenols. This combina...