Hydrolysis and Transport Characteristics of Phospholipid Complex of Alkyl Gallates: Potential Sustained Release of Alkyl Gallate and Gallic Acid.

Phospholipid complexes of alkyl gallates (A-GAs) including ethyl gallate (EG), propyl gallate (PG), and butyl gallate (BG) were successfully prepared by the thin film dispersion method. HPLC-UV analysis in an everted rat gut sac model indicated that A-GAs can be liberated from phospholipid complexes, which were further hydrolyzed by intestinal lipase to generate free gallic acid (GA). Both A-GAs and GA are able to cross the membrane, and the hydrolysis rate of A-GAs and the transport rate of GA are positively correlated with the alkyl chain length. Especially, compared with the corresponding physical mixtures, the phospholipid complexes exhibit slower sustained-release of A-GAs and GA. Therefore, the formation of phospholipid complexes is an effective approach to prolong the residence time in vivo and additionally enhance the bioactivities of A-GAs and GA. More importantly, through regulating the carbon skeleton lengths, controlled-release of alkyl gallates and gallic acid from phospholipid complexes will be achieved.