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Formulation Of A Phenol-Rich Extract From Unripe Olives (Olea Europaea L.) In Microemulsion To Improve Its Solubility And Intestinal Permeability

Lorenzo Cecchi, Vieri Piazzini, Mario D’Ambrosio, Cristina Luceri, Federica Rocco, Marzia Innocenti, Giulia Vanti, Nadia Mulinacci, Maria Camilla Bergonzi

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The beneficial properties of phenolic compounds from Olea europaea L. are well-known. An olive extract (OE) was prepared from unripe olives (Moraiolo cultivar). The study aimed to formulate OE into a microemulsion (ME) in oral dosage form. OE was extracted from olives with EtOH:H2O (80:20) and characterized by HPLC-DAD. ME composition was stated by a solubility and pseudo-ternary diagram. The ME was chemically and physically characterized, and its stability at 4 °C was analyzed for three months. The ability of the formulation to ameliorate the solubility and the intestinal permeability of OE was evaluated by a Parallel Artificial Membrane Permeability Assay (PAMPA) assay and Caco-2 cells. The total phenolic content of the extract was 39% w/w. The main constituent was oleuropein (31.0%), together with ligstroside (3.1%) and verbascoside (2.4%). The ME was prepared using Capryol 90 as the oily phase, and Cremophor EL and Transcutol (2:1) as surfactant and co-surfactant, respectively. ME droplet size was 14.03 ± 1.36 nm, PdI 0.20 ± 0.08, ζ-potential −1.16 ± 0.48. Stability of ME was confirmed for at least three months. The formulation was loaded with 35 mg/mL of OE, increasing the solubility of the extract by about four times. The enhanced permeability of OE was evaluated by PAMPA, as demonstrated by the Pe value (1.44 ± 0.83 × 10−6 cm/s for OE hydroalcoholic solution, 3.74 ± 0.34 × 10−6 cm/s for OE-ME). Caco-2 cell transport studies confirmed the same results: Papp was 16.14 ± 0.05 × 10−6 cm/s for OE solution and 26.99 ± 0.45 × 10−6 cm/s for OE-ME. ME proved to be a suitable formulation for oral delivery.