Illicium verum L. (Star Anise) Essential Oil: GC/MS Profile, Molecular Docking Study, In Silico ADME Profiling, Quorum Sensing, and Biofilm-Inhibiting Effect on Foodborne Bacteria

Abstract

Illicium verum, or star anise, has many uses ranging from culinary to religious. It has been used in the food industry since ancient times. The main purpose of this study was to determine the chemical composition, antibacterial, antibiofilm, and anti-quorum sensing activities of the essential oil (EO) obtained via hydro-distillation of the aerial parts of Illicium verum. Twenty-four components were identified representing 92.55% of the analyzed essential oil. (E)-anethole (83.68%), limonene (3.19%), and α-pinene (0.71%) were the main constituents of I. verum EO. The results show that the obtained EO was effective against eight bacterial strains to different degrees. Concerning the antibiofilm activity, trans-anethole was more effective against biofilm formation than the essential oil when tested using sub-inhibitory concentrations. The results of anti-swarming activity tested against P. aeruginosa PAO1 revealed that I. verum EO possesses more potent inhibitory effects on the swarming behavior of PAO1 when compared to trans-anethole, with the percentage reaching 38% at a concentration of 100 µg/mL. The ADME profiling of the identified phytocompounds confirmed their important pharmacokinetic and drug-likeness properties. The in silico study using a molecular docking approach revealed a high binding score between the identified compounds with known target enzymes involved in antibacterial and anti-quorum sensing (QS) activities. Overall, the obtained results suggest I. verum EO to be a potentially good antimicrobial agent to prevent food contamination with foodborne pathogenic bacteria.

Keywords: Illicium verum; antibiofilm; chemical composition; in silico; pathogenic bacteria; pharmacokinetics.

Figure 1

Chemical structure of the compounds identified in I. verum EO. All compounds’ names (1–24) are listed in Table 1.

Figure 2

Biofilm formation ability of pathogenic bacteria on various materials. Values are the average of at least three independent determinations. Small letters are used to compare mean values of the optical density (OD_{570 nm}) for each strain with three different materials. Means followed by the same letters are not significantly different at p < 0.05 based on Duncan’s multiple range test.

Figure 3

Biofilm inhibition capacity of I. verum EO and trans-anethole against S. aureus ATCC 6538. MIC = 0.048 mg/mL for the EO and trans-anethole. Values are the average of at least three independent determinations. Means followed by the same letters are not significantly different at p < 0.05 based on Duncan’s multiple range test. Small letters are used to compare mean values of different concentrations for trans-anethole, and capital letters are used to compare means between different concentrations of I. verum EO.

Figure 4

Biofilm eradication capacity of I. verum EO and trans-anethole on polystyrene (A) and glass (B) surfaces against S. aureus ATCC 6538. Values are the average of at least three independent determinations. Means followed by the same letters are not significantly different at p < 0.05 based on Duncan’s multiple range test. Small letters are used to compare mean values of different concentrations for trans-anethole and I. verum EO for each strain.

Figure 5

Effect of different MIC values of I. verum EO and trans-anethole on violacein inhibition in C. violaceum ATCC 12472.

Figure 6

Boiled egg model of studied I. verum EO compounds. The names of the compounds are listed in Table 1.

Figure 7

Bioavailability polygons of compounds identified in I. verum EO based on their physicochemical parameters using ADMET properties. Names of the compounds (1–24) are the same as in Table 1.

Figure 8

Two-dimensional and three-dimensional residual interaction network of the anisyl methyl ketone–1HD2 complex and anisyl methyl ketone–1JIJ complex.

Figure 9

Two-dimensional and three-dimensional residual interaction network of the anisyl methyl ketone–2XCT complex and anisyl methyl ketone–2UV0 complex.

Figure 10

Two-dimensional and three-dimensional residual interaction network of anisyl methyl ketone–3IX3.