Use of N-oxide and cationic surfactants to enhance antioxidant properties of (+)-usnic acid loaded liposomes

The influence of the presence of synthetic structurally related N-oxide and corresponding cationic surfactants with different chain lengths on the properties of 1,2-dimyristoyl-sn-glycero-3-phosphocholine liposomes was investigated. Their potentiality as delivery systems of (+)-usnic acid was also evaluated by studying its entrapment efficiency and its antioxidant activity. In fact, (+)-usnic acid has many pharmacological properties that, as many natural substances, are often strictly linked to their antioxidant power. N-oxide surfactants can enhance this property and improve the efficacy of the system. Based on this premise, we verified how and to what extent the molecular structure of liposomes components affects this effect: the best antioxidant effectiveness was observed when (+)-usnic acid was included in liposomes containing the N-oxide surfactant with C14 alkyl chain. Our results underline the importance of the hydrophilic/hydrophobic balance of the monomer in determining the properties of the aggregates in which it is included. © 2019 Elsevier B.V.