Anti‐inflammatory and anti‐cancer activity of citral: Optimization of citral‐loaded solid lipid nanoparticles (SLN) using experimental factorial design and LUMiSizer®

&NA; Essential oils containing monoterpenes are widely used in pharmaceuticals and cosmetic products on account of their wide range of bioactive properties (including anti‐cancer activity). Two monoterpenes (citral and geraniol) were firstly tested for their anti‐inflammatory activity in a RAW 264.7 cell line, demonstrating citral to have enhanced capacity to inhibit NO production (ca. 84% for citral and 52% for geraniol at the lowest tested concentration of 5 &mgr;g/ml). As citral showed higher NO inhibitory activity than geraniol, to measure the level of cytotoxicity of citral, AlamarBlue reduction assay was run in two cell models (non‐tumoral HaCaT and tumoral A431). Citral exhibited a strong cytotoxic effect in both cell lines, i.e. cell viability lower that 10% after 24 h exposure at 100 &mgr;g/ml of monoterpene. An optimized solid lipid nanoparticles (SLNs) formulation for citral was further developed by design of experiments (22 factorial design), followed by accelerated stability testing (LUMiSizer®). An optimal SLN composed of 1 wt% of citral, 4 wt% of lipid and 2.5 wt% surfactant were successfully produced by hot high pressure homogenization (hot HPH) showing a mean particle size (Z‐Ave) of 97.7 nm and polydispersity index of 0.249. The produced formulations were analyzed in a high‐end dispersion analyzer LUMiSizer® to characterize any demixing phenomena, demonstrating to be long‐term stable at room temperature (25 °C), exhibiting very low instability indices (0.032 after production and 0.042 after one month of storage).