# Formulation Strategies to Improve Oral Bioavailability of Ellagic Acid
## 4 Formulation Strategies for Improving EA Oral Bioavailability
### Inclusion Complexes
#### 4.3.1 EA Inclusion in Cyclodext (CDs)
In this regard, it has to be remembered that very low Z-potential values (\(\zeta<5\) mV) usually translates in particles with high tendency to agglomerate that means physical instability in solution. On the contrary, increasing the charge associated with the particle i.e., \(\zeta\pm 30\) mV or higher, usually prevents particles sticking after collision [65; 66]. Moreover, EE was around 69% and, as highlighted by X-ray diffraction, in the polymeric structure EA was present either in the amorphous form or as a solid-state solution. The release profiles showed that only about 20% of loaded EA was released after 24 h, suggesting strong retention of EA in the NS network. A pharmacokinetic study in rabbits indicated that oral administration of EA-\(\beta\)-CD NS increased EA bioavailability by more than 2-fold if compared to the free EA suspension. In a more recent work, a useful analysis of the preparation processes and experimental conditions for obtaining inclusion complexes was reported [67]. Three inclusion methods were considered, i.e., stirring-ultrasonic, ultrasonic, and grinding. In the first method, which led to the highest EE (84%), EA, dissolved in a small amount of ethanol, was added by slowly dripping into HP-\(\beta\)-CD aqueous solution under stirring, then the mixture was sonicated for 20 min, and finally kept under stirring at rt for further 18 h. The suspension was filtered, concentrated with rotary evaporator and vacuum dried to obtain the inclusion compound. Process conditions were optimized by an orthogonal test design, in which EA:HP-\(\beta\)-CD molar ratio, ethanol concentration, inclusion time and temperature were considered to be experimental parameters. The experimental design showed that EA:HP-\(\beta\)-CD-polar ratio of 1:2, ethanol concentration of 60%, inclusion time of 36 h, and inclusion temperature of 20 \({}^{\circ}\)C were the best conditions. Recently, [PERSON] et al. failed in realizing an effective complexation in HP-\(\beta\)-CD as the first study did, possibly because in this case the phase solubility studies were performed at rt instead of 30 \({}^{\circ}\)C [68]. In fact, a linear increase in EA solubilization was achieved only in alkaline solution, where raising HP-\(\beta\)-CD concentrations up to 300 mM led to a total EA concentration only 2.8-times higher than that without CD. However, the low stability constant of the complex (K1:1 = 4.5 M-1) resulted in a low complexation efficiency with an EA:CD stoichiometric ratio equal to 1:45. Concerning the procedure, the inclusion complex was prepared by spray drying a suspension of EA:CD 1:1 molar ratio in 0.1 M NaOH solution. Furthermore, also methyl-\(\beta\)-CD was used without success, since no complexing ability was found either in water or in basic solution. Finally, Caco-2 cells were employed in an in vitro model of invasive Candida albicans infection to test the bioactivity of EA complexes, but no statistically significant difference was observed in terms of antifungal activity between free or complexed EA, suggesting that complexation apparently did not improve antimycotic efficacy.