SLOW-RELEASE OF COPAIBA OIL ADSOLUBILIZED INTO LAYERED DOUBLE HYDROXIDES: A PROMISING MATERIAL FOR SKIN OINTMENTS

In this work, Zn/Al layered double hydroxides intercalated with dodecyl sulfate ion (DS) in molar ratios (Zn2+/Al3+) 2:1, 3:1 and 4:1 were synthesized by co-precipitation method and then they were adsolubilized with essential oil of copaiba in the concentrations of 3, 5, 10, 13 and 15% wt/wt to be used as carriers in therapeutic ointments for skin injury treatments. The XRD results showed a diffraction pattern corresponding to the structure of LDHs with the presence of diffraction peaks referring to the basal reflection planes. Typical stretching and vibration bands of copaiba essential oil in FTIR spectra confirmed the adsolubilization process. The oil release plateau in the ointment was above 80% at normalized values in a time of approximately 20 h, the time required for dissolution and release of molecules adsorbed in the layered structure of the material for molar ratios 2:1 and 3:1 and the release of the solubilized molecules in the interlayer space. In contrast, LDH with a 4:1 molar ratio showed slower release and did not reach the plateau in 48 h, as this material has the ability to retain oil molecules in the LDH for longer, causing a slower release in relation to other molar ratios. The analysis for the non-intercalated copaiba oil showed a gradual increase in the concentration of the oil in the ointment, indicating a different curve profile.