Antioxidant-containing monoolein aqueous dispersions: a preliminary study

The present study describes a preliminary study on the use of monoolein aqueous dispersions (MADs) as delivery systems for antioxidant molecules, namely, ascorbyl palmitate (AP) and alpha-tocopherol (AT). MAD, produced by emulsifying monoolein (4.5% w/w) in water and poloxamer 407 (0.5% w/w) as emulsifier, was characterized in terms of size, morphology, and antioxidant activity by mean of PCS, cryo-TEM, and (2,2-diphenyl-1-picrylhydrazyl) assay. MAD-AP or MAD-AT gave rise to a bimodal size distribution with mean size around 200 nm. All the preparations stored at 25 °C showed quite stable size at least up to 90 days. Cryo-TEM images confirmed MAD size distribution and indicated different MAD morphologies as a function of the loaded antioxidant molecule. Indeed, in the case of MAD-AP, vesicles and cubosomes with the typical inner cubic structure were observed, while vesicles and hexosomes were shown for MAD-AT. The encapsulation efficiency of both antioxidants reached more than 90% with respect to the total amount of drug used for MAD preparation. Moreover, AP and AT antioxidant activity was retained after encapsulation, and in vitro Franz cell experiments showed that the MAD enabled to better control the drug release. These preliminary results suggest that MAD formulations could be further investigated as a potential delivery system for antioxidant supplementation in dietary or cosmetic fields.