Chemical composition and antimicrobial activity of essential oil obtained from the rhizomes of Kaempferia champasakensis: in vitro and molecular docking studies

Kaempferia champasakensis Picheans. & Koonterm (Zingiberaceae) is locally known as "Dia Lien hoa trang" in Vietnam. Despite a previous study on the essential oils (EO) of K. champasakensis leaves, no other studies have reported the chemical components and biological activities of K. champasakensis. Therefore, this study aims to identify the chemical constituents of the EO from the rhizomes of K. champasakensis and evaluate their antimicrobial activity, which has been re-confirmed through molecular docking studies. The gas chromatography-mass spectrometry (GC/MS) analysis revealed sixty-one constituents (95.4%) present in the EO of K. champasakensis rhizomes. Among them, camphene (40.7%), alpha-pinene (10.2%), and beta-pinene (7.6%) were identified as the main compounds in the EO. Bioassays indicated its antimicrobial activity in the order of inhibitory effectiveness: Staphylococcus aureus > Enterococcus faecalis approximate to Candida albicans > Bacillus cereus approximate to Escherichia coli > Salmonella enterica > Pseudomonas aeruginosa. The molecular docking study of ligand-protein interactions involving the major constituents of EO was conducted against target proteins related to Staphylococcus aureus, Enterococcus faecalis, Candida albicans, Bacillus cereus, and Escherichia coli main activities. The results revealed that alpha-pinene exhibited strong binding affinity against E. coli, beta-pinene demonstrated more effective inhibition against E. faecalis and B. cereus, and camphene primarily exhibited activity against C. albicans and S. aureus. Furthermore, the analysis of interactions between the main compounds and the selected proteins was elucidated in the current study. This is the first time that chemical components of the EO of K. champasakensis rhizomes and their antimicrobial activity have been reported. These findings contributed to the basis for further studies on the chemical compositions and biological effects of K. champasakensis.