Acute Dermal Irritation and Acute Dermal Toxicity Tests of Centella asiatica (L.) Herb Extract Nanoemulgel in Comparison with Centella asiatica (L.) Herb Extract Nanoemulsion

Abstract: The application scale of topical formulations made with natural ingredients continues to expand, but safety remains a core concern for the industry. Especially nanoformulations that increase the permeabilityof active ingredients in the skin will potentially increase the toxicity of the formulation. Therefore, the industry commonly combines nanoemulsions with gel bases to produce nanoemulsion gels to improve the formulation’s viscosity and skin safety. The novelty and main objective of this study is to compare the safety of the nanoemulsion and nanoemulsion gel (CHEN) prepared by Centella asiatica (L.) extract. Tests were conducted in accordance with the standard specifications of the OECD 404 acute skin irritation test and OECD 402 acute skin toxicity test. The measurement results showed that CHEN had a particle size of 78.67 ± 0.84 nm and a pH value of 5.09 ± 0.00. Acute skin irritation in rabbits showed that CHEN and the nanoemulsion had primary irritation indices of 0.02 ± 0.13 and 0.08 ± 0.4, respectively, and were categorized as negligible. The acute skin toxicity in rats showed no mortality or significant toxic symptoms, indicating an LD50 value of more than 2000 mg/kg BW. Body weight observations in the nanoemulgel showed an increase of 4.5 ± 13.44 g at the highest dose, whereas in the nanoemulsion preparation there was a decrease of -27.5 ± 12.02 g. The results of liver histopathology analysis showed no necrosis or fatty degeneration, mild to moderate hydropic degeneration, and minimal inflammation, which were reversible. In conclusion, CHEN has the potential to be a safer topical preparation than nanoemulsion preparations. However, further studies, such as subacute, subchronic, and chronic toxicity tests, are still needed because this study was limited to a 14-day observation period. In addition, long-term stability testing is needed to support the development of safer and more stable preparations.