An eco-friendly and effective method for isolating essential oil from fresh Kaempferia galanga L.: Process optimization based on entropy weight method and response surface methodology

The bioactive properties of essential oil are strongly associated with their chemical composition. In this work, a novel method of salt-enhanced homogenization pretreatment coupled with solvent-free microwave extraction (HP-SSFME) was developed for extracting essential oil (KGEO) from fresh Kaempferia galanga rhizomes, which significantly improved the extraction efficiency. Gas chromatography was employed to measure the contents of the main active components, ethyl p -methoxycinnamate (EPMC) and ethyl cinnamate (EC) in the essential oil. The extraction process was optimized by the Box-Behnken Design using the comprehensive scores of the yields of EPMC, EC, and KGEO obtained by the entropy weight method. The optimal parameters were determined as follows: amount of sodium chloride was 1.60 %, homogenization speed of 15000 r/min, homogenization time of 4 min, microwave irradiation power of 300 W, microwave irradiation time of 23 min. Under these conditions, the KGEO yield was 5.10 %, EPMC yield was 3.81 %, EC yield was 0.89 %. Compared with the conventional methods, the HP-SSFME method not only significantly increased the extraction yield of KGEO but also remarkably enhanced the yields of EPMC and EC. Additionally, the HP-SSFME method has low CO 2 emission and energy consumption, highlighting its environmental friendliness. Moreover, in terms of antibacterial activity, the HP-SSFME outperformed other methods, demonstrating a more powerful and extensive inhibitory effect against a range of bacteria. This study provides a valuable reference for the efficient extraction and quality control of essential oils from Kaempferia galanga rhizomes.