Synthesis and characterization of novel flavonoid derivatives via sequential phosphorylation of quercetin

Flavonoids are naturally-occurring polyphenolics that have been implicated in a wide range of biological activities. The major obstacles to flavonoid applications are the poor solubility in common solvents. Phosphorylation of flavonoids yields a new class of flavonoid derivatives which are very soluble in aqueous solutions and hence have the potential to be used in biological studies. We hereby report the sequential phosphorylation of Quercetin leading to the synthesis of Quercetin pentaphosphate (QPP), Apigenin triphosphate (ATRP), 5,4′-Quercetin Diphosphate (5,4′-QDP) and 4′-Quercetin monophosphate (4′-QP) with solubility of 848 mg/mL, 367 mg/mL, 315 μg/mL and 106 μg/mL respectively. The synthesis of 4′-QP, 5,4′-QDP, QPP and ATRP was successful with 85%, 60.5%, 56% and 99% yield respectively. These compounds have been characterized using ¹H NMR, ¹³C NMR, ³¹P NMR.