Essential Oil Extracted from the Leaves of Curcuma Longa L.: Application of an Agro-Industrial Residue in the Development of Anti-Inflammatory Nanoemulsions Intended for Skin Delivery

Curcuma longa L. leaves are a residual material of the rhizome harvest and arouse interest in the investigation of their properties.

This study aimed to extract and characterise the essential oil (EO) from C. longa leaves and compare the feasibility of delivering of the EO and its major compound in nanoemulsions for the further evaluation of in vitro anti-inflammatory activity and preliminary safety profile.

The EO was obtained by hydrodistillation and analysed by gas chromatography (GC-MS). The nanoemulsions were prepared in a high-pressure homogeniser and characterised. The in vitro anti-inflammatory activity was measured using an LPS-stimulated macrophage model (RAW 264.7). The preliminary safety profile was evaluated by cell culture (HaCaT and MRC-5) and by the hen’s egg-chorioallantoic membrane test (HET-CAM).

In the CG-MS analysis, 10 compounds were identified: α-phellandrene (49.93%), terpinolene (27.10%), and 1,8-cineole (15.41%) being the main compounds. All nanoemulsions showed droplet size < 300 nm, polydispersity index < 0.2, and zeta potential <-30 mV, indicative of monodisperse formulations without the tendency for droplet aggregation. The nanoemulsions showed an α-phellandrene content greater than 91.00%. The assessment of the irritant potential by HET-CAM assay shows no irritating effects on the membrane. In the cytotoxicity evaluation, no significant alterations were observed in HaCaT and MRC-5 cells. Regarding the in vitro anti-inflammatory activity, the inhibition of NO production by the EO nanoemulsion was evidenced with a low cytotoxicity rate for α-phellandrene concentrations below 125 µg/mL.

These results show the potential of the EO extracted from leaves, which are a waste product from rhizome harvesting.