# Formulation Strategies to Improve Oral Bioavailability of Ellagic Acid
## 4 Formulation Strategies for Improving EA Oral Bioavailability
### EA Encapsulated in Polymeric Carriers
#### 4.4.1 Eudragit\({}^{\circledR}\) Microspheres
Concerning EA release at pH 7.4, all products exhibited a rapid initial release followed by a slower sustained phase, with PVA NPs being the fastest, because PVA hydrophilic groups favor water penetration into the NPs compared to the more lipophilic DMAB. However, the release study was not performed simulating the pH conditions of the whole gastrointestinal tract. To study the permeability of NPs, an in situ intestinal study was performed on rats based on the close loop method, even though the disappearance of drug from the luminal side, used for determining permeation, not always correlates with the rate of absorption of the drug in the systemic circulation. EA-DMAB NPs showed the highest uptake (87%) in accordance with their smaller size and higher hydrophobicity. The antioxidant activity was assessed in cell free system and in yeast cell culture model, confirming the good scavenging activity of the encapsulated pomeranate acid. The same research group also investigated the feasibility of EA-loaded PCL NPs in comparison to PLGA NPs using the same emulsion-diffusion-evaporation method, but with an important modification: during the primary emulsion step EA underwent a rapid precipitation that caused its low entrapment, so the authors added the stabilizer to the polymer solution to increase EA solubility [22]. As expected, EE increased from 42% to 52% for DMAB-PLGA NPs and from 55% to 62% for PVA-PLGA NPs, not much different from EE of DMAB-PCL and PVA-PCL NPs (47% and 57% respectively). Since PCL is a slower degrading polymer compared to PLGA, its release profiles yielded slower release rates. The antioxidant potential of EA-DMAB NPs was assessed by evaluating their protective action against cyclosporine A-induced nephrotoxicity in rats: both PLGA- and PCL-based NPs were 3-fold more effective than free EA in kidney protection, thus indicating the improved bioavailability of the encapsulated EA. Unfortunately, PLGA NPs major drawback is rapid opsonization, so that their systemic circulation time is too short. To address this issue, EA was encapsulated in PLGA NPs grafted with poly (ethylene glycol) (PEG) chains to escape to the reticuloendothelial system [73]. In a proof of principle study, NPs were prepared by the double emulsion-solvent evaporation method. Two dichloromethane stock solutions, containing PLGA-PEG and EA respectively, were mixed, added to 200 \(\mu\)L of phosphate-buffered saline solution (PBS) and sonicated. This primary _w/o_ emulsion was emulsified in PVA 1% _w/v_ aqueous solution by sonication. Subsequently, this _w/o/w_ emulsion was first diluted with PVA 1%, then heated for dichloromethane evaporation and finally the obtained NP were dialyzed and lyophilized. The NP showed a diameter of 175 nm with PDI of 0.14. In vitro biological studieson MCF-7 and Hs578T breast cancer cell lines proved a significant activity enhancement of EA in the encapsulated form, being its IC50 values more than 2-fold lower than those of the free form. In a further attempt to curb the phagocytic activity, a combination of CS and PEG was considered to be surface coating material for EA-PLGA NPs [74]. The NPs were prepared by o/w single emulsion-solvent evaporation method as follows. EA and PLGA were separately dissolved in chloroform and emulsified with PVA 2% _w/w_ aqueous solution containing 12% _w/w_ CS and 5% _w/w_ PEG 2 kDa through sonication. The emulsion was stirred overnight up to complete evaporation of the organic solvent. The coated CS-PEG-PLGA NPs were compared to PLGA NPs and PEG-PLGA NPs prepared in the same way. EE was always about 65%, while the mean hydrodynamic diameter was 220 nm for PLGA NPs and CS-PLGA NPs, and 255 nm for CS-PEG-PLGA NPs. As expected, positive charges were present on the surface of CS-PLGA NPs and CS-PEG-PLGA NPs (\(\zeta\) = +27 and \(\zeta\) = +38 mV, respectively); on the contrary, a negative zeta potential characterized PLGA NPs (\(\zeta\) = \(-\)10 mV).