Nanoemulsions to enhance oral bioavailability of Vitex Agnus-castus extract

Vitex agnus castus L. is a native species of the Mediterranean region. The main characteristic constituents are: bicyclic diterpenes, iridoid glycosides (agnuside), lipophilic flavonoids (casticin, penduletin), hydrophilic flavones (luteolin, isovitexin), triglycerides [1]. Therapeutic indications are: premenstrual syndrome (PMS) including symptoms such as mastodynia or mastalgia and menstrual cycle disorders such as polymenorrhoea, oligomenorrhoea or amenorrhoea [2]. In vitro and in vivo experiments have shown that Agnus castus extracts have dopaminergic, prolactin-inhibiting activity through interaction with dopamine D2 receptors. Indeed an increase in serum levels of prolactin is a frequent cause of menstrual irregularities, pre-menstrual syndrome and mastodynia [3]. The project is aimed at developing new oral innovative formulations, which can overcome the limited oral bioavailability increasing the therapeutic efficacy, making “innovative” the formulations with established efficacy. After the optimization of HPLC-DAD-QTOF analytical method for qualitative and quantitative characterization of Agnus castus extract from commercial source, nanoemulsions (NEs) were selected as lipid carriers. Two extract-loaded NEs were prepared: NE1 consisting of triacetin as oil phase, labrasol as surfactant and Cremophor EL as cosurfactant, and NE2 formed by triacetin as the oil phase labrasol and Tween 20 as surfactant and cosurfactant. Both NEs contain about 40 mg/ml of extract. The droplets in the NEs appear dark, and the surroundings are bright under transmission electron microscopy with an average diameter of 11.15 ± 0.07nm and a polydispersity index (PdI) of 0.07 ± 0.01 for NE1 and 8.61 ± 0.08nm and PdI of 0.19 ± 0.05 for NE2. The solubility of the extract was improved about 5 times by NEs compared to water. The passive intestinal permeation by Parallel Artificial Membrane Permeation Assay (PAMPA) and the permeation across Caco-2 cell after preliminary cytotoxicity studies were evaluated. NEs show a good solubilizing effect of the constituents of the extract, as evidenced by different amount of flavonoids and iridoids present in the donor compartment, compared to aqueous solution. The total amount of constituents permeated from NEs into donor compartment is greater than that permeated from saturated aqueous solution.