β-Carotene, α-tocoferol and rosmarinic acid encapsulated within PLA/PLGA microcarriers by supercritical emulsion extraction: Encapsulation efficiency, drugs shelf-life and antioxidant activity

Abstract

β-Carotene (β-CA) is largely used antioxidant with a high sensibility to oxidation when in contact with light and temperature. To improve its shelf life and develop a nutraceutical formulation it was encapsulated into poly-lactic-co-glycolic acid (PLGA) and poly-lactic acid (PLA) carriers using Supercritical Emulsion Extraction (SEE). α-Tocoferol (α-TOC) and Rosmarinic Acid (RA) were proposed as excipients to improve product shelf-life. Different emulsion formulation conditions, such as compositions and mixing rate were used; whereas, SEE operating conditions in the counter-current tower were fixed at 80 bar and 38 °C with an L/G ratio of 0.1. In these conditions, PLA and PLGA carriers with sizes ranges between 1.5 ± 0.5 μm and 0.3 ± 0.1 μm were fabricated with Encapsulation Efficiencies (EEs) between 50–80%. The co-encapsulation of α-TOC with β-CA gained to prolonged drug shelf life; whereas, RA co-encapsulation was not successfully and, in some cases, also reduced β-CA-EE. The poor loading experienced, in the case of RA, was probably due to its high solubility into the high-pressure mixture of carbon dioxide and organic solvent formed during the emulsion extraction. This behaviour was defined “co-extraction effect” and may limit the application of SEE technology in the encapsulation of molecules soluble in the mixture obtained during oily phase extraction. Shelf-life studies were performed after UV irradiation for ten days and after carriers storage for 2 years at 4 °C. The better performance in terms of shelf life was observed for PLGA capsules loaded with β-CA/α-TOC; whereas, PLA formulation with β-CA/α-TOC showed a superior antioxidant activity with an half minimal Inhibitory Concentration (IC50) against the free radical DPPH of 1.8 mg/mL of carriers.