Optimization of Extraction Conditions of Antioxidant Components from Henna (Lawsonia Inermis) Using Response Surface Method (RSM)

The Henna plant (Lawsonia inermis) is considered one of the most important medicinal plants due to its high concentration of phenolic chemicals (such as coumarins, flavonoids, naphthalene, and gallic acid derivatives), triterpenoids, steroids, and aliphatic hydrocarbons. To optimize the extraction of phenolic compounds from the methanol extract of Henna leaves, an ultrasonic method was employed and compared with the immersion method. The experiments were conducted using a Box-Behnken design to assess the impact of independent variables on response performance (i.e., the extraction efficiency of phenolic compounds) and to predict the optimal response value. The impact of various factors, including temperature (10, 25, and 40 °C), time (5, 20, and 30 minutes), and pH (6, 7, and 8), on the process efficiency was examined. The findings indicated that the highest extraction efficiency of phenolic compounds, reaching 49.8%, was achieved after 30 minutes at an extraction temperature of 32°C and pH 6.6. Under these conditions, the extraction yield of phenolic compounds was over 15 mg of gallic acid per gram of the initial powder, with an IC50 value of 0.48 mg/ml. A comparison of the two extraction methods revealed that the ultrasound method achieved a 49.8% higher extraction efficiency of active plant compounds compared to the immersion method. Specifically, the extraction efficiency increased from 10.28 mg/g (in terms of gallic acid) with the immersion method to 15.4 mg/g using the ultrasonic method.