Liposomal nanodelivery systems generated from proliposomes for pollen extract with improved solubility and in vitro bioaccessibility

This study offers a suitable and easy proliposome-liposome method that enhances the encapsulation ability of liposome structures on poor water-soluble extracts. Pollen phenolic extract (PPE) was studied to show applicability in the proposed method. The poor water-soluble PPE (0.2%, w/v) was encapsulated by liposomes generated from proliposomes (P-liposomes) that were prepared via high-pressure homogenization technique without using any organic solvents and high temperature. Only a few drops of ethanol were used to dissolve poor water-soluble compounds in PPE during the preparation of P-liposomes. The trace amount of ethanol maintained the improvement of PPE solubility in P-liposome dispersion, hence the in vitro bioaccessibility and bioactivity of PPE incorporated in P-liposomes increased. Thus, higher encapsulation efficiency was found in P-liposomes compared to conventional liposomes (C-liposomes) in which the EE was 75 and 73%, respectively. To increase the physical stability of liposome structures, the surface of both P-liposomes and C-liposomes was covered with chitosan. There were found small changes between P-liposomes and C-liposomes in terms of mean diameter size and zeta potential. On the other hand, the bioactivity of encapsulated PPE showed differences in P-liposomes and C-liposomes. The antioxidant capacity of PPE in P-liposomes enhanced approximately two times in CUPRAC and three times in DPPH assays. Also, in vitro bioaccessibility of PPE in P-liposomes increased approximately 4 and 2 folds, respectively, regarding total phenolics and flavonoids. To our knowledge, this is the first report about the increment of encapsulation behavior of liposome structures on low water-soluble extract within an aqueous media.