Exploring the Stability of a Marine Polyphenol Dieckol by Ultraviolet Absorption Spectroscopy

Dieckol is a marine polyphenol with pluripotent pharmacological activity and an excellent safety profile, demonstrating great therapeutic potential for various chronic and viral diseases. Despite its significance, dieckol remains understudied in terms of physicochemical properties and optimal dosage forms for drug delivery or pharmaceutical manufacturing. Given dieckol&quots complex polyphenolic nature, its biological properties may be sensitive to factors such as pH and oxygen, which are commonly encountered in physiological systems and industrial processes. In this study, we explored the UV absorption spectra of dieckol in organic solvent DMSO and aqueous solutions at different pH levels, assessing its stability and reactivity. Dieckol showed high stability in DMSO, indicating its suitability for stock solutions. Absorption spectra at pH 2 and 5 represented the protonated structure, while spectra at pH 7.4 and 12 represent the deprotonated(anionic) structures. We estimated the average pKa of dieckol for the first time using a UV absorption spectroscopic method, yielding a pKa value of 8.1 ± 0.4. Our findings highlight the importance of controlling pH and oxygen concentration in dieckol solutions and provide valuable insights into the physicochemical properties of this promising marine polyphenol in drug formulation, delivery and physiological aspects.